Windrowing poultry litter after a broiler house has been sprinkled with water1

Windrowing poultry litter after a broiler house has been sprinkled with water1 Abstract In-house windrowing of poultry litter between broiler flocks has been promoted as a management practice to improve the litter condition upon chick placement. Before the onset of the current study, low-pressure sprinklers were used during the grow-out period in a broiler house. Different methods of windrowing were then utilized to determine the effect each had on litter composition. Covered, turned, and static 9 d windrow treatments, and one non-windrowed control were applied to a broiler house containing litter used over multiple flock grow-outs. The house was divided into 16 6 × 6 m plots with each treatment being applied to 4 blocks within the house. Litter from each plot was analyzed for particle size, moisture, N, NH3, P, K, pH, and temperature over a 20-day period, with d 20 representing 7 d after chick placement. All variables except particle size were statistically different. Of all the treatments, the covered treatment showed the greatest reduction in moisture over the 20-day period. Nitrogen content was lowest in the turned treatment. Ammonia decreased from d 9 to 20. Both the covered and static treatments were able to reach recommended temperatures in both the core and the periphery of the windrows. Conclusively, in-house windrowing after utilizing low-pressure sprinklers did not improve N retention, reduce NH3 volatilization, or decrease P or K in the litter compared to the control. However, the temperatures obtained in the periphery and core of the covered and static treatments show potential for eliminating pathogens present in the litter. DESCRIPTION OF PROBLEM The poultry industry currently re-uses bedding material over several broiler flock grow-outs. This strategy is practiced due to the increasing cost and decreased availability of traditional pine shaving bedding material. It is also evident that built-up litter yields less footpad dermatitis than fresh litter [1]. However, when broilers are grown on the same bedding or litter material over several flocks, challenges arise. These challenges may include an increase in N, P, and K, as well as NH3. Used litter also can lead to disease outbreaks. In-house windrowing is a technique used by the poultry industry to improve the quality of used broiler litter. The technique is very similar to composting, where litter is piled into a single or multiple rows that extend the length of the broiler house [2]. The piles are then allowed to generate heat over a specific amount of time to reduce pathogenic organisms [3]. The main differences between composting and windrowing are the time it takes to perform, their temperature profiles, and the residual material at the end of the process [2]. To effectively windrow used litter, the moisture content of the litter must exceed 32% but remain less than 35% [4]. However, most litter management practices during a broiler grow-out are designed to reduce litter moisture, and in Mississippi the average litter moisture content is around 24.8%, which can make it hard to accomplish an effective windrowing program [5]. Recently, low-pressure water sprinklers, an alternative or supplement to the commonly used evaporative cooling pads, have been evaluated as a method for cooling birds within a broiler house without reducing the house temperature [6]. This new alternative replaces or supplements the evaporative cooling pad system with a low-pressure (<50 psi) sprinkler system. Not only is the sprinkler system meant to lower the body temperature of poultry, but also lower the airborne particulate matter and NH3 [7]. The use of the sprinkler system will result in temperatures that are similar to or slightly lower than the outside environment. As well, the resulting humidity in the house will be relatively close to the outside environment [6]. The humidity for sprinkler cooling will be lower than that of a traditional cool-cell system and thus may promote a drier climate for the birds. Although the house can run hotter, with improper management, a sprinkler system in the broiler house may increase the moisture content of the litter over the length of the grow-out. If litter moisture is higher at the end of the grow-out, then in theory a more effective windrowing process should occur. Though the concept of higher moisture in the litter contradicts good management practices (GMP), a moisture content above Mississippi's average 24.8% but between 32 and 35% is important, because higher moisture content is directly related to the windrow temperature, and higher temperature can potentially inactivate disease-causing organisms more efficiently [8]. It has been demonstrated by Macklin et al. [9] that an in-house windrow reaching slightly above 50°C for 48 h has the potential to reduce anaerobic and aerobic bacteria and eliminate Salmonella and Campylobacter within the core of the windrow. Fifty degrees Celsius (50°C) also has been an instrumental temperature in reducing pathogenic bacteria within an in-house windrow, and this temperature is also capable of killing or inactivating most viruses, fungi, and parasite eggs [10, 11]. Thus, temperature is necessary for improving litter quality and flock welfare. The EPA 503b rule addresses the temperature requirements to effectively treat litter: exceed 40°C for 120 h and within the 120 h exceed 55°C for 4 h; however, these temperatures are hard to obtain throughout the entirety of a windrow [12, 13, 14]. Previous research has indicated that when litter within the average Mississippi moisture content is windrowed, only the core of the windrow is able to meet temperatures necessary to inactivate disease-causing organisms, not the outer exterior [12, 13]. The need to evenly inactivate pathogens in the litter may be solved by the additional water added to the litter by the sprinkler system. Despite the benefit of reducing pathogenic organisms by windrowing, it is important to determine the effects that the addition of water may have on other parameters related to litter quality (NH3 levels, pH, etc.). If the moisture content of the litter were to exceed 35%, an increase in NH3 production may occur, which could lead to poor chick quality and high mortality rates. Miles et al. [15] noted that moisture and temperature have a direct effect on NH3 volatilization. Higher temperature and a critical point of moisture content will increase NH3 volatilization. However, if the moisture content is below or above the critical point, NH3 volatilization will decrease [15]. Higher moisture also can lead to nutrient runoff due to the excess of free water in the windrow. The excess free water also can lead to compression of the litter, which corresponds to a reduction in particle size and therefore porosity. However, an increase in windrow temperatures from the compression and decrease in porosity of the litter also can cause a decrease in litter pH [16, 17]. Therefore, the objective of this study was to determine the impact that windrowing has on litter quality when the broiler house has utilized low-pressure sprinklers throughout the grow-out period. MATERIALS AND METHODS House Layout One commercial broiler house with the dimensions of 121.9 M long x 13.1 M wide was utilized in this study. The house was divided into 4 blocks, and each block contained 4 treatments that were randomly assigned, providing a total of 16 plots for evaluation (Figure 1). There were 8 plots on either side of the house, and the plots were centered in the middle of the house, leaving 33.5 M on either end of the house. During the treatment term, the house was closed, with no ventilation. Figure 1. View largeDownload slide Treatment arrangement in a commercial broiler house. The commercial house used was 121.9 m in length x 13.1 m in width. There were 16 plots measuring 6.1 × 6.1 m. Four plots denote a block, with each treatment being represented within a block. Treatments included: 1) a treatment in which litter was de-caked but not windrowed (Control), 2) a treatment in which litter was de-caked prior to windrowing, windrowed, and allowed to sit for 9 d (Static), 3) a treatment in which the litter was de-caked prior to windrowing, windrowed, turned in on itself on d 4, and then allowed to sit for 5 d (Turned), and 4) a treatment in which litter was de-caked prior to windrowing, windrowed, covered with 1.2 mm thick plastic, and allowed to sit for 9 d (Covered). There were 2 rows of plots, with 8 plots on either side. Thirty-three-and-a-half meters of space were not utilized on either the evaporative cool cell or exhaust fan ends of the house (not drawn to scale). Figure 1. View largeDownload slide Treatment arrangement in a commercial broiler house. The commercial house used was 121.9 m in length x 13.1 m in width. There were 16 plots measuring 6.1 × 6.1 m. Four plots denote a block, with each treatment being represented within a block. Treatments included: 1) a treatment in which litter was de-caked but not windrowed (Control), 2) a treatment in which litter was de-caked prior to windrowing, windrowed, and allowed to sit for 9 d (Static), 3) a treatment in which the litter was de-caked prior to windrowing, windrowed, turned in on itself on d 4, and then allowed to sit for 5 d (Turned), and 4) a treatment in which litter was de-caked prior to windrowing, windrowed, covered with 1.2 mm thick plastic, and allowed to sit for 9 d (Covered). There were 2 rows of plots, with 8 plots on either side. Thirty-three-and-a-half meters of space were not utilized on either the evaporative cool cell or exhaust fan ends of the house (not drawn to scale). Within the broiler house, the litter consisted of built-up litter that had been previously used by 9 consecutive flocks with the grow-out periods lasting 63 days. The litter profile was 10 to 13 cm deep. There were no previous disease or pathogen concerns associated with the litter in the house. As well, windrowing and chemical amendments were applied previously to the litter. The litter was windrowed every other flock and chemical amendments were applied if necessary between flocks. Low-pressure Sprinkler System During the previous grow-out period, before the onset of this study, the broiler house used a commercial low-pressure sprinkler system (Weeden Sprinkler System) [18]. The system involves low-pressure sprinkler nozzles, which are comparable to normal yard sprinklers with a spinner head. The sprinklers were mounted from the ceiling and ran the length of the house on 2 lines located 3 m from each sidewall with 20 sprinkler nozzles on either line for a total of 40 nozzles. Each nozzle had an output of 15 mL of water per s over an area of 42 m2 [18]. The sprinklers became active when the birds reached 5 wk of age. The Weeden controller utilized a 3-stage program that operated specifically on time intervals. The first stage began when the broilers reached 5 wk of age. The 3 set stages in the sprinkler controller were named stages 1, 2, and 3. Stage 1 was set to run every 30 min, stage 2 was set to run every15 min, and stage 3 was set to run every 5 minutes. At each stage, the system ran for only 20 s between each time interval. The temperature increment between each stage was set for 2.8°C, while the cool-cell system ran 1.7°C above the sprinkler. In 2014, from July 24 to September 25, the low-pressure sprinkler system utilized 80,962 liters of water, while the evaporative cooling pad utilized 133,281 liters. Treatments Each of the 4 treatments was randomly assigned to one of the 4 blocks creating 16 plots. There was a total of 4 replications for each treatment. The treatments consisted of a non-windrowed control, a static windrow, a turned windrow, and a covered windrow. The control was de-caked on d 0 and had no windrow application applied to it. The static treatment was de-caked, windrowed, and then allowed to sit for the following 9 days. The turned treatment was de-caked, windrowed, turned in on itself on d 4, and then allowed to sit for an additional 5 days. The covered treatment was de-caked, windrowed, covered with 1.2 mm thick plastic, and then allowed to sit for 9 days. The individual windrows, when formed, were 6 m long x 1.5 m wide x 1 m high in depth. Windrows were formed using a tractor equipped with a litter windrow blade [19]. On d 4, turned windrows were turned in on themselves using a skid steer loader. On d 9, all windrows were broken down in their respective plots. The house was then closed for 4 additional d (d 13) until day-old chicks were placed back in the house for the next commercial grow-out. No analysis was performed on placed chicks. Chicks were supplied feed and water ad libitum. Chicks used in this experiment were treated in compliance with the Guide for the Care and Use of Agricultural Animals in Research and Teaching [20]. Sample Collection On day 0, the previous flock was transported for processing. Litter samples were collected on d 4, when the turned treatment was being rolled in on itself; d 9, when all windrows were leveled out; d 13, when the next flock's chicks were placed; and d 20, 7 d after chick placement. Handfuls of litter were collected (at least 20 g) from 5 random locations at varying depths within each plot and then pooled into a Ziploc bag [21]. There were 16 total bags of litter for each d of litter collection. At the lab, 200 g of litter were transferred to smaller Whirl-Pak bags to be analyzed for N, P, and K [22]. Particle Size Particle size of the litter was determined using a Ro-Tap Sieve Shaker [23]. In duplicate, 100 g of litter were weighed and then placed into the first set of sieves (No. 4, 6, 8, 10, 16, 20, and 40). The first set of sieves was allowed to sift for 5 minutes. Upon completion, the litter that was able to sift to the bottom pan was placed on the top of a second set of sieves (No. 50, 70, 100, 140, 200, and 270). The second set of sieves was set in the Ro-Tap and allowed to sift for another 5 minutes. Each sieve was weighed, and then the following equation was used [24]:   \begin{equation*} {{\rm{d}}_{{\rm{gw}}}}{\rm{ = lo}}{{\rm{g}}^{ - 1}}\left[ {\frac{{\sum\nolimits_{{\rm{i = 1}}}^{\rm{n}} {\left( {{{\rm{W}}_{\rm{i}}}\log {{{\rm{\bar d}}}_{\rm{i}}}} \right)} }}{{\sum\nolimits_{{\rm{i = 1}}}^{\rm{n}} {{{\rm{W}}_{\rm{i}}}} }}} \right] \end{equation*} Where: dgw is geometric mean diameter or median size of particles by mass (mm), di is normal sieve aperture size of the ith sieve (mm), Wi is the mass on the ith sieve (g), and n is the number of sieves +1 (pan). Litter Moisture Litter moisture was measured in duplicate for each plot. Each individual litter sample was measured into 15 g samples. The wet weight of the sample was obtained before being placed into a drying oven [25]. Each sample was then placed in a 0.325 m2 drying oven for 24 h at 105°C. Once 24 h had passed, the samples were removed from the drying oven and weighed to determine their dry weight. Moisture content was calculated using the following equation [26]:   \begin{equation*} {\rm{MC}}(\% ) = \frac{{{{\rm{W}}_{{\rm{wet}}}} - {{\rm{W}}_{{\rm{dry}}}}}}{{{{\rm{W}}_{{\rm{wet}}}}}} \times 100 \end{equation*} Where: MC (%) is the percentage of moisture present or moisture content, Wwet is the wet weight, and Wdry is the dry weight. Nitrogen, Phosphoric Acid, and Potash All samples were analyzed by the Mississippi State Chemistry Lab. Phosphoric acid and potash were analyzed by AOAC methods 2006.03a and 2006.03, respectively [27, 28]. Nitrogen was analyzed by the DUMAS method utilizing the Rapid N Cube [29]. NH3 Ammonia generation for the litter was measured on d 9, 13, and 20. Measurements were not recorded on d 4 due to the windrows still in formation. Ammonia production off the litter at floor level was analyzed using an infrared photoaccoustic multi-gas analyzer with a dynamic flux chamber, using the design by Woodbury et al. [30, 31]. NH3 was calculated based on the chamber footprint, sampling time, and the mass of NH3 in the acid trap [30]. The NH3 gas being emitted off the litter was sampled for approximately 10 min to allow the infrared photoaccoustic multi-gas analyzer to calibrate. Ammonia levels were then recorded at 11, 12, and 13 minutes. The 3 readings were then averaged to determine NH3 production. pH Litter pH was analyzed by measuring 10 g of each litter sample in duplicate and then transferring each sample to a 500 mL beaker. Ultra purified water (100 mL) was then added to the beaker containing the 10 g of litter and stirred for approximately 5 min [25]. Using an Accumet Excel XL60 probe [32], the litter-water mixture was tested to obtain a pH reading [33]. Temperature Thermochron i-Button temperature sensors were used to record temperature throughout the house [34]. There were 2 sensors in each plot, both attached to a wooden stake that had one sensor submerged in the litter and the other sensor just below the litter surface. The sensor that was submerged in the litter recorded the temperature at the core of the windrow. The other sensor that was just below the litter's surface recorded the periphery temperature of the windrow. For all treatments, except the control, the periphery sensor was submerged 5.1 cm under the litter surface of the windrow. The control treatment's core sensor was 5.1 cm under the litter surface, while the periphery sensor was just below the surface. The sensors recorded the temperature every 20 min during the experiment, in accordance with their programming. In this experiment, the temperature data collected up to d 9 were used. Temperature data for the outside environment for Mississippi State University (33.4691°, −88.7822°) were collected from the National Climatic Data Center database for the entirety of this project (Table 1) [35]. The temperature of the house during the first 7 d of chick placement was recorded using a Rotem controller and is also displayed in Table 1 [36]. Table 1. Outside ambient temperature from d 1 to d 20 (September 25, 2014 to October 15, 2014). All data retrie- ved from Mississippi State University station, NCDC (33.4691° to 88.7822°). Average inside temperatures were obtained from the Rotem Platinum Plus controller protocol set in accordance with industry standards. Day  Outside temperature  Inside temperature    Max°C  Low°C  Average°C  0  28  14  26  1  29  15  41  2  29  17  44  3  28  17  45  4  28  18  44  5  31  17  43  6  31  16  42  7  32  17  41  8  28  19  38  9  27  9  29  10  21  9  –  11  26  12  –  12  27  17  –  13  31  19  32  14  31  18  32  15  32  19  32  16  31  19  32  17  31  19  32  18  28  21  32  19  29  14  32  20  20  11  30  Day  Outside temperature  Inside temperature    Max°C  Low°C  Average°C  0  28  14  26  1  29  15  41  2  29  17  44  3  28  17  45  4  28  18  44  5  31  17  43  6  31  16  42  7  32  17  41  8  28  19  38  9  27  9  29  10  21  9  –  11  26  12  –  12  27  17  –  13  31  19  32  14  31  18  32  15  32  19  32  16  31  19  32  17  31  19  32  18  28  21  32  19  29  14  32  20  20  11  30  View Large Statistical Analysis All data were analyzed using a randomized complete block design with a split plot over days. The means were separated using Fisher's protected LSD and were considered significant at P ≤ 0.05 [37, 38]. RESULTS AND DISCUSSION A delicate balance exists between improving litter quality and pathogen reduction in poultry litter. This balance is highly dependent on the moisture content of the litter. Litter quality is determined on the basis of the poultry litter's particle size, nitrogen retention, ammonia volatilization, levels of phosphorus and potassium, and pH. Pathogen reduction is obtained through high temperatures. High moisture inclusion will allow the litter to obtain optimal temperatures for pathogen reduction; however, litter quality may experience detrimental effects to overall quality due to the high moisture. Because there is such a thin line concerning moisture content, it is advantageous to utilize a strategy that balances both litter quality and pathogen reduction. The results from the current windrowing experiment in which low-pressure sprinklers were utilized demonstrated no difference in particle size (PS) among d or treatments (P = 0.9226; P = 0.0645; data not shown). Therefore, PS was determined not to be a concern for windrowing, as previous studies also have shown. Keener et al. [39] demonstrated that PS was not an issue if moisture was ≤45% at the start of windrowing and “mechanical mixing” was utilized during or at the end of the windrowing process. In the current study, litter moisture was ≤45% at the beginning of windrowing, and at the end, all treatments were mechanically mixed with a skid steer loader. Although there was not a significant difference for PS, there were differences for moisture content, N, NH3, P, K, and pH. The amount of moisture present in poultry litter can affect NH3 volatilization and microbial growth. Moisture is necessary to produce a windrow that reduces pathogens effectively because the elevated windrow temperature needed to inactivate bacteria is directly influenced by moisture content [8]. As stated previously, 50°C has been seen to reduce, inactivate, or destroy most of the major concerns in litter, such as pathogens, viruses, and parasite eggs [10, 11]. The average moisture content of litter in Mississippi is 24.8%, yet the recommended moisture content for an effective windrow is between 32 and 35% [5, 7]. Due to the use of a low-pressure sprinkler system in the latter wk of broiler rearing, a moisture content above Mississippi's average litter moisture was expected. Even though the sprinklers use a controlled amount of water that creates a wind-chill effect on the birds, some of the sprinkled water also may reach the litter. Therefore, correct management is critical to maintaining proper litter conditions. In this study, the moisture content for all treatments was above 40% at d 4; however, by d 20, the moisture content of litter for all treatments either met or fell below the recommended level of 32% (Figure 2). For the covered treatment, d 4 demonstrated the highest moisture content (60%) compared to all other treatments. However, by d 20 the moisture content of the covered treatment was reduced to 24%, the lowest moisture content of any treatment. The high moisture content for the covered treatment on d 4 is most likely due to the impermeable tarp being placed over the windrow, preventing moisture from evaporating into the air. After the tarp was removed on d 9, the moisture was then able to evaporate and revert to below recommended levels. Only the turned treatment remained at the recommended level of 32% on d 20. For all treatments, we expected the litter to dry out from d 13 to d 20. This is due to the fact that chicks were placed back into the house and ventilation and brooding were required. Overall, the litter moisture content was not in the effective range for windrowing from d 4 to d 9, as it was well above the recommended level. This high-moisture content present in the litter had the potential to increase the quantity of pathogens present in the litter, especially if the windrows did not reach the recommended temperatures for reducing pathogens [40]. Along with a possible increase in pathogens, a higher moisture content in the litter also could result in higher nitrogen loss, ammonia volatilization, and further degradation of litter [8, 41]. Figure 2. View largeDownload slide Treatment by d interaction for percent litter moisture (moisture %). The column consisting of the diagonal lines representsthe static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-e) are significantly different (P = 0.04; SEM = 3.39; N = 4). Figure 2. View largeDownload slide Treatment by d interaction for percent litter moisture (moisture %). The column consisting of the diagonal lines representsthe static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-e) are significantly different (P = 0.04; SEM = 3.39; N = 4). The results of this study indicated that the static 9 d windrow had the highest nitrogen concentration (4.60%) when compared to all other windrow treatments ((P = 0.02); Figure 3). However, all treatments were still below the recommended N level of 5 to 7% [42]. No differences among the control, covered, or turned treatments were determined. N loss usually occurs more in composted manure because of the higher rate of denitrification, which was not discovered among the treatments in this study, as the static treatment had the highest N concentration [43]. However, according to Mahimairaja et al. [43], denitrification occurs under anaerobic conditions, and nitrogen is lost in the form on N2. Therefore, it was expected that the covered treatment would have the greatest loss of N, because a 1.2 mm thick plastic tarp, which should have prevented aerobic conditions, covered the windrow. The plastic also did not allow for the evaporation of moisture from the surface of the windrow, providing an environment more suitable for denitrification. However, it was concluded that the covered, turned, and control treatments were not different in terms of loss of N. Figure 3. View largeDownload slide N levels for all sample plots within a treatment were averaged together to attain the mean N content (%) for each treatment. The column consisting of the diagonal lines represents the static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-b) are significantly different (P = 0.02; SEM = 0.04; N = 16). Figure 3. View largeDownload slide N levels for all sample plots within a treatment were averaged together to attain the mean N content (%) for each treatment. The column consisting of the diagonal lines represents the static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-b) are significantly different (P = 0.02; SEM = 0.04; N = 16). Although N was not different among the covered, turned, or control treatments, all 3 were different when compared to the static treatment but not by an alarming amount (<0.21%). Flory et al. [44] demonstrated the effectiveness of turned windrows in a commercial setting vs. a control. Their results determined that there were no differences in nutrient value or N level among treatments; however, a numerical decrease in N level was apparent among treatments. In the current study, the higher N content demonstrated for the static treatment may be the result of the high temperatures the treatment obtained in its core and periphery. Lavergne et al. [4] demonstrated a correlation between total N and the maximum temperature after the addition of water in static in-house windrows. The results indicated that a windrow that reached a higher temperature had a higher N content than a windrow that had an average temperature [4]. Because the static treatment in our study had one of the highest temperatures among all other treatments, it can be suggested that the elevated N may have been a result of the high temperature. Another reason for the loss of nitrogen during windrowing is ammonia volatilization. Henry and White [41] discovered that a large quantity of N lost during windrowing was due to ammonia volatilization. In the current study, no differences among treatments were found for NH3 production (data not shown). This finding was surprising because poultry manure typically contains 5 to 7% total N, with 60 to 75% of the N in the form of uric acid [42, 45], and when uric acid breaks down, it produces NH3 [46]. Keener et al. [39] reported a reduction in N loss through NH3 volatilization when windrows were covered. Therefore, lower NH3 generation was expected from the static and turned windrow treatments in the current study when compared to our covered treatment. Although there were no differences found for NH3 production among treatments, this result may have been influenced by the high initial moisture contents, which also could have led to the findings for N content. Because NH3 volatilization is one of the major pathways for N loss, it is important to monitor NH3 production over time. However, the monitoring of NH3 production is important for more than just N loss, NH3 production is also a major welfare concern [45]. Over the course of this study, the concentration of NH3 generated directly off the litter was determined to decrease (d 9, 684.67 ppm; d 13, 585.96 ppm; and d 20, 111.96 ppm) (Figure 4). The high NH3 generation at d 9 and 13 may be the result of the high litter moisture created by the low-pressure sprinkler system in concurrence with the evaporative cooling system. As mentioned before, uric acid is less likely to degrade into NH3 if the litter is kept dry [46]. Even as the level of NH3 produced decreased, on d 13 the NH3 concentration being generated by the litter was well above a safe level for day-old chicks. On d 20, the NH3 being generated by the litter into the flux chamber was reduced to 111.96 ppm. The reduction in NH3 production from d 13 to d 20 was most likely the direct result of ventilation and the use of the brooders, as it would dry the litter and therefore reduce NH3 generated by the litter. It is important to note that in this study, the NH3 monitored was that generated directly by the litter into the flux chamber and not the air surrounding the chicks. Due to the ventilation protocol in place in the broiler house, no chicks were under conditions in which the atmospheric NH3 in the house exceeded 25 ppm, the maximum limit for atmospheric ammonia at bird height [47]. Figure 4. View largeDownload slide Ammonia levels of all plots were averaged together for each sampling d to get the mean NH3 levels (ppm) for each day. The light gray column represents the mean NH3 of all plots on d 9. The dark gray column represents the mean NH3 for all plots on d 13. The white column represents the mean NH3 for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.0002; SEM = 56.90; N = 16). Figure 4. View largeDownload slide Ammonia levels of all plots were averaged together for each sampling d to get the mean NH3 levels (ppm) for each day. The light gray column represents the mean NH3 of all plots on d 9. The dark gray column represents the mean NH3 for all plots on d 13. The white column represents the mean NH3 for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.0002; SEM = 56.90; N = 16). In the current study it also was determined that potash and phosphoric acid concentrations increased over time (Figures 5 and 6). Potash increased over a 20-day period at 3.98, 3.93, 4.19, and 4.08% on d 4, 9, 13, and 20, respectively. Phosphoric acid increased over a 20-day period at 5.49, 5.63, 6.07, and 6.12% on d 4, 9, 13, and 20, respectively. It is important to note that an increase in the concentration of P in litter is not a favorable outcome for litter quality. If there is too much P in the litter, then when applied as fertilizer, the high P concentrations could run off into nearby streams, estuaries, or lakes. N, P, and K are all needed for life; however, too much in the environment can cause eutrophication [48]. Eutrophication can result in an increase of algae and deoxygenation of the water, directly killing the ecosystem in that body of water [48, 49]. In this study, the treatments on d 20 had P2O5 and K2O levels of 6 and 4%, respectively. According to a study done by the University of Georgia Cooperative Extension, composted litter has 3 and 2.3% levels of P2O5 and K2O, respectively [50]. One possible explanation for the high level of P and K is the reuse of the litter over several flocks [4, 51]. A study that examined the trend of nutrient content in Mississippi, determined an increasing trend of nutrients until the 20th flock [51]. It also was noted that litter management that utilizes total clean-out will experience lower nutrient levels [51]. With the increasing concern for the environment and the ecosystem, the increase of both P and K is not a desirable outcome. Figure 5. View largeDownload slide Potash (K2O) content for all samples plots was averaged together for each sampling d to obtain the mean potash concentration (%) over a 20-day period. The black column represents the mean potash of all the plots on d 4. The light gray column represents the mean potash of all plots on d 9 when the windrows were broken down. The dark gray column represents the mean potash for all plots on d 13 when chicks were placed into the broiler house. The white column represents the mean potash for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.02; SEM = 0.06; N = 16). Figure 5. View largeDownload slide Potash (K2O) content for all samples plots was averaged together for each sampling d to obtain the mean potash concentration (%) over a 20-day period. The black column represents the mean potash of all the plots on d 4. The light gray column represents the mean potash of all plots on d 9 when the windrows were broken down. The dark gray column represents the mean potash for all plots on d 13 when chicks were placed into the broiler house. The white column represents the mean potash for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.02; SEM = 0.06; N = 16). Figure 6. View largeDownload slide Phosphoric acid (P2O5) levels for all plots were averaged together for each sampling d to obtain the mean phosphoric acid content (%) for each day. The black column represents the mean phosphoric acid of all the plots on d 4. The light gray column represents the mean potash of all plots on d 9. The dark gray column represents the mean potash for all plots on d 13. The white column represents the mean potash for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.0001; SEM = 0.10; N = 16). Figure 6. View largeDownload slide Phosphoric acid (P2O5) levels for all plots were averaged together for each sampling d to obtain the mean phosphoric acid content (%) for each day. The black column represents the mean phosphoric acid of all the plots on d 4. The light gray column represents the mean potash of all plots on d 9. The dark gray column represents the mean potash for all plots on d 13. The white column represents the mean potash for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.0001; SEM = 0.10; N = 16). Liang et al. [8], while evaluating the effects of in-house broiler litter windrowing, noticed an increase in both total P and K in the windrow treatments that were under high-moisture conditions. It was deduced that the increase was relative to P, Ca, and K being the most reliable nutrients to show degradation; but it also was found that the control treatment had greater degradation than the windrow treatments [8]. However, it should also be mentioned that in that study, the control treatment had higher moisture (21.5%) than the highest moisture windrow treatment (19.6%) from the very beginning [8]. In respect to windrowing poultry litter after the utilization of low-pressure sprinkler systems in conjunction with an evaporative cooling system, higher P and K over time may be from the higher degradation occurring as a result of moisture and temperature, which is comparative to the study conducted by Liang et al. [8]. Litter moisture also can have an impact on litter pH. As % moisture is increased, the pH of the litter becomes more basic [52]. In reference to the average pH of poultry litter in Mississippi, which is 8.4, all treatments were in the average range except for the covered treatment on d 4 (8.75) [5]. The pH for the turned treatment was initially low and then increased by d 9 and 13 but reverted to a lower pH by d 20 (8.39, 8.48, 8.55, and 8.26 on d 4, 9, 13, and 20, respectively). Both the static and control windrows demonstrated an increase in pH on d 9, but the pH then decreased from d 13 thru d 20 (Figure 7). The static windrow treatment started at a pH of 8.36 on d 4, increased to 8.43 on d 9, and then decreased to 8.38 and 8.06 on d 13 and 20, respectively. The pH for the control treatment increased from 8.40 on d 4 to 8.59 on d 9, but then decreased to 8.48 and 8.16 on d 13 and 20, respectively. For the covered windrow treatment, pH was initially high but over time decreased (8.75, 8.67, 8.36, and 8.02 on d 4, 9, 13, and 20, respectively). However, none of the windrowing treatments or the control treatment reduced the pH to a level that would improve litter quality. If the pH could have been reduced below 7.5, the NH3 concentration also may have been reduced [53]. According to Groot Koerkamp [45], a pH of 7 or below allows NH3 to be bound as ammonium, thus preventing NH3 volatilization. The more basic the pH is (above 5.5), the more readily uric acid is broken down [45]. A lower pH would have stunted NH3 production, substantially yielding more N retention in the litter. Therefore, the results of this study suggest that no windrowing technique improved litter quality when compared to the control treatment, which may be attributed to the higher moisture present at the onset of this study from the utilization of a low-pressure sprinkler system in tangent with an evaporative cooling system. Figure 7. View largeDownload slide Interaction between d and treatment for litter pH (pH). The column consisting of the diagonal lines represents the static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-h) are significantly different (P = 0.003; SEM = 0.70; N = 4). Figure 7. View largeDownload slide Interaction between d and treatment for litter pH (pH). The column consisting of the diagonal lines represents the static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-h) are significantly different (P = 0.003; SEM = 0.70; N = 4). Though the moisture, N, NH3, P, K, and pH results all indicated the treatments did not have a positive effect on litter quality, the temperature results may have impacted the litter environment in a positive manner. According to the EPA 503b rule, for a windrow to effectively reduce pathogens, it must exceed 40°C for 120 h and within the 120 h exceed 55°C for 4 h [14]. To further this rule, it has been recommended that the windrow exceed 50°C for at least 24 h [10]. Other studies, such as Barker et al. [13], Lavergne et al. [4], and Macklin et al. [9], have attempted to reach this benchmark but have been unable to obtain these temperatures in the periphery of the windrow. Additionally, previous research conducted by Schmidt et al. [54], utilizing a 42-point grid, established that the EPA 503b rule could be achieved only within approximately 38.4 ± 26.2% of a windrow. In the current study, both the periphery and core temperatures were monitored using a 2-point system. The static and covered treatments both met the criteria for the EPA 503b rule in the core and periphery (Figures 8 and 9). The turned treatment met the criteria for the EPA 503b rule only in its core (Figure 8). Although a 2-point method is not the most accurate procedure at predicting the entire windrow temperature, utilizing this method is still a valuable resource [9]. Because both the static and covered treatments were effective in reaching 40°C for 120 h, 50°C for 24 h, and 55°C for 4 h in their periphery and core, both treatments have the potential to reduce pathogens, diseases, and parasites present in the litter. Figure 8. View largeDownload slide Core temperatures for all samples were averaged together for each sampling d to attain the mean core temperature (°C) for each day. The black solid line (——) represents the turned treatment, the dotted line (······) represents the static treatment, the dash-dot line (-·-·-·-) represents the covered treatment, and the dashed line (− − −) represents the control treatment. Figure 8. View largeDownload slide Core temperatures for all samples were averaged together for each sampling d to attain the mean core temperature (°C) for each day. The black solid line (——) represents the turned treatment, the dotted line (······) represents the static treatment, the dash-dot line (-·-·-·-) represents the covered treatment, and the dashed line (− − −) represents the control treatment. Figure 9. View largeDownload slide Peripheral temperatures for all samples were averaged together for each sampling d to attain the mean peripheral temperature (°C). The black solid line (——) represents the turned treatment, the dotted line (······) represents the static treatment, the dash-dot line (-·-·-·-) represents the covered treatment, and the dashed line (− − −) represents the control treatment. Figure 9. View largeDownload slide Peripheral temperatures for all samples were averaged together for each sampling d to attain the mean peripheral temperature (°C). The black solid line (——) represents the turned treatment, the dotted line (······) represents the static treatment, the dash-dot line (-·-·-·-) represents the covered treatment, and the dashed line (− − −) represents the control treatment. It is evident from this study that the quality of the litter was affected by the inclusion of additional moisture through the utilization of a low-pressure sprinkler system during the grow-out period. Because of these effects, there were no improvements in N, NH3, P, K, and pH at the conclusion of the windrowing procedure. The temperature in the windrows, however, was increased to an effective range in order to reduce potential pathogens that may have been present in the litter. In future studies, it will be imperative to find a balance between moisture and temperature, so that both litter quality and pathogen reduction can be maximized. CONCLUSIONS AND APPLICATIONS The higher moisture content in the litter resulted in higher NH3 volatilization, a lower percentage of N, and higher P and K over time, after the utilization of in-house windrowing. The moisture content in the litter was above the recommended level of 32 to 35% at the onset of windrowing; however, by d 20, only the static treatment was within the recommended level, and all other treatments and control had been reduced to <30% moisture. Windrowing and management practices reduced the moisture to a safer level for the birds. The higher moisture content in the litter increased the ability of the static and covered treatments to reach the desired temperatures in both the core and surface of those treatments, which is favorable for reducing pathogens, according to the EPA 503b rule. The relatively high moisture present in the litter may be a result of the low-pressure sprinklers being utilized in conjunction with the evaporative cooling system. Further studies should be conducted to compare the effects of the low-pressure sprinklers being utilized alone vs. low-pressure sprinklers being utilized in tangent with evaporative cooling pads on in-house windrowing of poultry litter. Footnotes 1 This publication is a contribution of the Mississippi Agricultural and Forestry Experiment Station. Primary Audience: Flock Supervisors, Quality Assurance Personnel, Researchers REFERENCES AND NOTES 1. Shepherd E. M. 2010. Environmental Effects on Footpad Dermatitis. M.S. Thesis . Univ. Georgia, Athens. 2. Miller F. C. 1996. Composting of municipal solid waste and its components. Pages 115– 154 in Microbiology of solid waste . Palmisano A. C., Barlaz M. A., ed. CRC Press, Boca Raton, FL. 3. Malone B. 2008. Bedding alternatives and windrowing programs. Pages 32– 34 in Proc. Virginia Poult. Health Manage. Semin. , Roanoke, VA. 4. Lavergne T. K., Stephens M. F., Schellinger D., Carney Jr W. and A.. 2006. In-house pasteurization of broiler litter. Publ. 2955. Louisiana State Univ. Agric. Center, Baton Rouge. 5. Terzich M., Pope M. J., Cherry T. E., Hollinger J.. 2000. Survey of pathogens in poultry litter in the United States. J. Appl. Poult. Res . 9: 287– 291. Google Scholar CrossRef Search ADS   6. Liang Y., Tabler G. T., Costello T. A., Berry I. L., Watkins S. E., Thaxton Y. V.. 2014. Cooling broiler chickens by surface wetting: Indoor thermal environment, water usage, and bird performance. Applied Engineering in Agriculture  30: 249– 258. 7. Wood D., Heyst B. V. 2014. Assessment of sprinklers on the removal efficiency of ammonia and particulate matter in a commercial broiler facility. Paper No. 141914276. ASABE, St. Joseph, MI. 8. Liang Y., Payne J. B., Penn C., Tabler G. T., Watkins S. E., VanDevender K. W., Purswell J. L.. 2014. Systematic evaluation of in-house broiler litter windrowing effects on production benefits and environmental impact. J. Appl. Poult. Res.  23: 625– 638. Google Scholar CrossRef Search ADS   9. Macklin K. S., Hess J. B., Bilgili S. F.. 2008. In-house windrow composting and its effects on foodborne pathogens. J. Appl. Poult. Res.  17: 121– 127. Google Scholar CrossRef Search ADS   10. Dumontet S., Dinel H., Baloda S. B.. 1999. Pathogen reduction in sewage sludge by composting and other biological treatments: A review. Biol. Agric. Hort.  16: 409– 430. Google Scholar CrossRef Search ADS   11. Jones P., Martin M.. 2003. A review of the literature on the occurrence and survival of pathogens of animals and humans in green compost. The Waste and Resource Action Programme. WebMD http://www.wrap. org.uk/downloads/LitReviewPathogensAnimalHuman Co-mpost. b1895775.pdf Accessed Jan. 2008. 12. Schmidt A. M., Davis J. D., Purswell J. L., Fan Z., Kiess A. S.. 2013. Spatial variability of heating profiles in windrowed poultry litter. J. Appl. Poult. Res.  22: 319– 328. Google Scholar CrossRef Search ADS   13. Barker K. J., Coufal C. D., Purswell J. L., Davis J. D., Parker H. M., Kidd M. T., McDaniel C. D., Kiess A. S.. 2011. In-house windrowing of a commercial broiler farm during the summer months and its effect on litter composition. J. Appl. Poult. Res.  20: 168– 180. Google Scholar CrossRef Search ADS   14. Code of Federal Regulations. 40 CFR.503 Appendix B. 15. Miles D. M., Rowe D. E., Cathcart T. C.. 2011. High litter moisture content suppresses litter ammonia volatilization. Poult. Sci.  90: 1397– 1405. Google Scholar CrossRef Search ADS PubMed  16. Agnew J. M., Leonard J. J.. 2003. The physical properties of compost. Compost Sci. Util.  11: 238– 264. Google Scholar CrossRef Search ADS   17. Dunlop M. W., Blackall P. J., Stuetz R. M.. 2015. Water addition, evaporation and water holding capacity of poultry litter. Science of the Total Environment  538: 979– 985. Google Scholar CrossRef Search ADS PubMed  18. Weeden Sprinkler System, Weeden Environments, Woodstock, Ontario. 19. Priefert Litter Back Blade , Priefert Manufacturing Co. Inc., Mt. Pleasant, TX. 20. Federation of Animal Science Societies. 2010. Guide for the Care and Use of Agricultural Animals in Research and Teaching. Champaign (IL): Federation of Animal Science. 21. Ziploc bags, S.C. Johnson and Son, Inc. Racine WI. 22. Whirl-Pak bags, Nasco, Fort Atkinson WI. 23. RO-TAP RX-29, W.S. Tyler, Mentor OH. 24. American Society of Agricultural and Biological Engineers. 2008. Method of Determining and Expressing Fineness of Feed Materials by Sieving. S319.4. Am. Soc. Agric. Biol. Eng. , St. Joseph, MI. PubMed PubMed  25. Fischer Scientific Research , Pittsburgh, PA. 26. American Society of Agricultural and Biological Engineers. 2007. Moisture relationships of plant-based agricultural products. Pages 596– 612 in ASABE Standards. 54th ed. Am. Soc. Agric. Biol. Eng. , St. Joseph, MI. 27. AOAC. 2005. Official Methods of Analysis . 18th Ed. AOAC INTERNATONAL. Gaithersburg, MD, Method 2006.03a. 28. AOAC. 2005. Official Methods of Analysis . 18th Ed. AOAC INTERNATONAL. Gaithersburg, MD, Method 2006.03. 29. Rapid N Cube, Elementar Analysensysteme GmbH , Hanau, Germany. 30. Woodbury B. L., Miller D. N., Eigenberg R. A., Nienaber J. A.. 2006. An inexpensive laboratory and field chamber for manure volatile gas analysis. Trans. ASABE  49: 767– 777. Google Scholar CrossRef Search ADS   31. Chillgard RT. MSA Safety , Murrysville, PA. 32. Accumet Excel XL-60, Fisher Scientific Research , Pittsburgh PA. 33. AOAC. 1995. Official Methods of Analysis . 16th ed. Assoc. Off. Anal. Chem. , Arlington, VA. 34. DS-1192 L, Dallas Semiconductor, Sunnyvale, CA. 35. Record of Climatological Observations. NCDC . Accessed Feb. 2017. https://www.ncdc.noaa.gov/cdo-web/datasets/GHCND/stations/GHCND:USC00228374/detail. 36. Rotem Platinum Plus, Rotem Control and Management, Petach-Tikva, Israel. 37. Steel R. G. D., Torrie J. H.. 1980. Principal and Procedures of Statistics: A Biometrical Approach . McGraw-Hill, Inc., New York, NY. 38. SAS Institute. 2012. Statistical Analysis Software. Version 9.4 . SAS Inst. Inc. Cary, NC. 39. Keener H., Wicks M., Michel F., Ekinci K.. 2014. Composting broiler litter. World's Poultry Science Journal  70, December 2014. 40. Wilkinson K. G., Tee E., Tomkins R. B., Hepworth G., Premier R.. 2011. Effect of heating and aging of poultry litter on the persistence of enteric bacteria. Poult. Sci.  90: 10– 18. Google Scholar CrossRef Search ADS PubMed  41. Henry S. T., White R. K.. 1993. Composting broiler litter from two management systems. Transactions of the ASAE  36: 873– 877. Google Scholar CrossRef Search ADS   42. Hansen R. C., Keener H. M., Dick W. A., Marugg C., Hoitink H. A. J.. 1990. Poultry manure composting: Ammonia capture and aeration control. Paper No. 904062. ASAE, St. Joseph's MI. 43. Mahimairaja S., Bolan N. S., Hedley M. J.. 1995. Denitrification losses of N from fresh and composted manures. Soil Biol. Biochem . 27. Pp. 1223– 1225. Google Scholar CrossRef Search ADS   44. Flory G. A., Peer R. W., Barlow B., Hughes D., Malone G. W., McElroy A. P.. 2008. Litter reconditioning as an alternative litter management strategy within the commercial poultry industry. Accessed June 2017. http://www.brownbearcorp.com/studies_and_research/Litter%20Reconditioning%20as%20an%20Alternative%20Litter%20Management%20%20Strategy%201.pdf. 45. Groot Koerkamp P. W. G. 1994. Review on emissions of Ammonia from housing systems for laying hens in relation to sources, processes, building design, and manure handling. Journal of Agricultural Engineering Research . 59: 73– 87. Google Scholar CrossRef Search ADS   46. Carey D. S. 1997. Minimizing N loss from poultry manure amended with ammonia sulfate. M.S. Thesis . The Ohio State University, Columbus, OH. 47. National Chicken Council. 2003. National Chicken Council Animal Welfare Guidelines and Audit Checklist . National Chicken Council, Washington, D.C. 48. Burgos S., Burgos S. A.. 2006. Environmental approaches to poultry feed formulation and management. Int. J. Poult. Sci . 5: 900– 904. Google Scholar CrossRef Search ADS   49. Ongley E. D. 1996. Control of Water Pollution from Agriculture. Ch. 3 . Food and Agriculture Organization of the United Nations. Rome. 50. Cunningham D. L., Ritz C. W., Merka W. C.. 2012. Best management practices for storing and applying poultry litter. The University of Georgia Cooperative Extension. Bulletin 1230. 51. Tabler G. T. 2015. Nutrient Content in Mississippi Broiler Litter . Extension Service of Mississippi State University. Publication 2878. Accessed 29 February 2016. 52. Zhang R., Wienhold B. J.. 2002. The effect of soil moisture on mineral nitrogen, soil electrical conductivity, and pH. Nutr. Cycl. Agroecosys . 63: 251– 254. Google Scholar CrossRef Search ADS   53. Carr L. E., Wheaton F. W., Douglas L. W.. 1990. Empirical models to determine ammonia concentrations from broiler chicken litter. Trans. ASAE  33: 0260– 0265. Google Scholar CrossRef Search ADS   54. Schmidt A. M. 2010. Design and Analysis of Static Windrow Piles for In-House Broiler Litter Composting. PhD Diss.  Mississippi State University, MS. Acknowledgements This publication is a contribution of the Mississippi Agricultural and Forestry Experiment Station (Mississippi State) and is supported by the United States Department of Agriculture Cooperative Agreement under MIS-322280. © 2017 Poultry Science Association Inc. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Poultry Research Oxford University Press

Windrowing poultry litter after a broiler house has been sprinkled with water1

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Oxford University Press
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© 2017 Poultry Science Association Inc.
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1056-6171
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1537-0437
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Abstract

Abstract In-house windrowing of poultry litter between broiler flocks has been promoted as a management practice to improve the litter condition upon chick placement. Before the onset of the current study, low-pressure sprinklers were used during the grow-out period in a broiler house. Different methods of windrowing were then utilized to determine the effect each had on litter composition. Covered, turned, and static 9 d windrow treatments, and one non-windrowed control were applied to a broiler house containing litter used over multiple flock grow-outs. The house was divided into 16 6 × 6 m plots with each treatment being applied to 4 blocks within the house. Litter from each plot was analyzed for particle size, moisture, N, NH3, P, K, pH, and temperature over a 20-day period, with d 20 representing 7 d after chick placement. All variables except particle size were statistically different. Of all the treatments, the covered treatment showed the greatest reduction in moisture over the 20-day period. Nitrogen content was lowest in the turned treatment. Ammonia decreased from d 9 to 20. Both the covered and static treatments were able to reach recommended temperatures in both the core and the periphery of the windrows. Conclusively, in-house windrowing after utilizing low-pressure sprinklers did not improve N retention, reduce NH3 volatilization, or decrease P or K in the litter compared to the control. However, the temperatures obtained in the periphery and core of the covered and static treatments show potential for eliminating pathogens present in the litter. DESCRIPTION OF PROBLEM The poultry industry currently re-uses bedding material over several broiler flock grow-outs. This strategy is practiced due to the increasing cost and decreased availability of traditional pine shaving bedding material. It is also evident that built-up litter yields less footpad dermatitis than fresh litter [1]. However, when broilers are grown on the same bedding or litter material over several flocks, challenges arise. These challenges may include an increase in N, P, and K, as well as NH3. Used litter also can lead to disease outbreaks. In-house windrowing is a technique used by the poultry industry to improve the quality of used broiler litter. The technique is very similar to composting, where litter is piled into a single or multiple rows that extend the length of the broiler house [2]. The piles are then allowed to generate heat over a specific amount of time to reduce pathogenic organisms [3]. The main differences between composting and windrowing are the time it takes to perform, their temperature profiles, and the residual material at the end of the process [2]. To effectively windrow used litter, the moisture content of the litter must exceed 32% but remain less than 35% [4]. However, most litter management practices during a broiler grow-out are designed to reduce litter moisture, and in Mississippi the average litter moisture content is around 24.8%, which can make it hard to accomplish an effective windrowing program [5]. Recently, low-pressure water sprinklers, an alternative or supplement to the commonly used evaporative cooling pads, have been evaluated as a method for cooling birds within a broiler house without reducing the house temperature [6]. This new alternative replaces or supplements the evaporative cooling pad system with a low-pressure (<50 psi) sprinkler system. Not only is the sprinkler system meant to lower the body temperature of poultry, but also lower the airborne particulate matter and NH3 [7]. The use of the sprinkler system will result in temperatures that are similar to or slightly lower than the outside environment. As well, the resulting humidity in the house will be relatively close to the outside environment [6]. The humidity for sprinkler cooling will be lower than that of a traditional cool-cell system and thus may promote a drier climate for the birds. Although the house can run hotter, with improper management, a sprinkler system in the broiler house may increase the moisture content of the litter over the length of the grow-out. If litter moisture is higher at the end of the grow-out, then in theory a more effective windrowing process should occur. Though the concept of higher moisture in the litter contradicts good management practices (GMP), a moisture content above Mississippi's average 24.8% but between 32 and 35% is important, because higher moisture content is directly related to the windrow temperature, and higher temperature can potentially inactivate disease-causing organisms more efficiently [8]. It has been demonstrated by Macklin et al. [9] that an in-house windrow reaching slightly above 50°C for 48 h has the potential to reduce anaerobic and aerobic bacteria and eliminate Salmonella and Campylobacter within the core of the windrow. Fifty degrees Celsius (50°C) also has been an instrumental temperature in reducing pathogenic bacteria within an in-house windrow, and this temperature is also capable of killing or inactivating most viruses, fungi, and parasite eggs [10, 11]. Thus, temperature is necessary for improving litter quality and flock welfare. The EPA 503b rule addresses the temperature requirements to effectively treat litter: exceed 40°C for 120 h and within the 120 h exceed 55°C for 4 h; however, these temperatures are hard to obtain throughout the entirety of a windrow [12, 13, 14]. Previous research has indicated that when litter within the average Mississippi moisture content is windrowed, only the core of the windrow is able to meet temperatures necessary to inactivate disease-causing organisms, not the outer exterior [12, 13]. The need to evenly inactivate pathogens in the litter may be solved by the additional water added to the litter by the sprinkler system. Despite the benefit of reducing pathogenic organisms by windrowing, it is important to determine the effects that the addition of water may have on other parameters related to litter quality (NH3 levels, pH, etc.). If the moisture content of the litter were to exceed 35%, an increase in NH3 production may occur, which could lead to poor chick quality and high mortality rates. Miles et al. [15] noted that moisture and temperature have a direct effect on NH3 volatilization. Higher temperature and a critical point of moisture content will increase NH3 volatilization. However, if the moisture content is below or above the critical point, NH3 volatilization will decrease [15]. Higher moisture also can lead to nutrient runoff due to the excess of free water in the windrow. The excess free water also can lead to compression of the litter, which corresponds to a reduction in particle size and therefore porosity. However, an increase in windrow temperatures from the compression and decrease in porosity of the litter also can cause a decrease in litter pH [16, 17]. Therefore, the objective of this study was to determine the impact that windrowing has on litter quality when the broiler house has utilized low-pressure sprinklers throughout the grow-out period. MATERIALS AND METHODS House Layout One commercial broiler house with the dimensions of 121.9 M long x 13.1 M wide was utilized in this study. The house was divided into 4 blocks, and each block contained 4 treatments that were randomly assigned, providing a total of 16 plots for evaluation (Figure 1). There were 8 plots on either side of the house, and the plots were centered in the middle of the house, leaving 33.5 M on either end of the house. During the treatment term, the house was closed, with no ventilation. Figure 1. View largeDownload slide Treatment arrangement in a commercial broiler house. The commercial house used was 121.9 m in length x 13.1 m in width. There were 16 plots measuring 6.1 × 6.1 m. Four plots denote a block, with each treatment being represented within a block. Treatments included: 1) a treatment in which litter was de-caked but not windrowed (Control), 2) a treatment in which litter was de-caked prior to windrowing, windrowed, and allowed to sit for 9 d (Static), 3) a treatment in which the litter was de-caked prior to windrowing, windrowed, turned in on itself on d 4, and then allowed to sit for 5 d (Turned), and 4) a treatment in which litter was de-caked prior to windrowing, windrowed, covered with 1.2 mm thick plastic, and allowed to sit for 9 d (Covered). There were 2 rows of plots, with 8 plots on either side. Thirty-three-and-a-half meters of space were not utilized on either the evaporative cool cell or exhaust fan ends of the house (not drawn to scale). Figure 1. View largeDownload slide Treatment arrangement in a commercial broiler house. The commercial house used was 121.9 m in length x 13.1 m in width. There were 16 plots measuring 6.1 × 6.1 m. Four plots denote a block, with each treatment being represented within a block. Treatments included: 1) a treatment in which litter was de-caked but not windrowed (Control), 2) a treatment in which litter was de-caked prior to windrowing, windrowed, and allowed to sit for 9 d (Static), 3) a treatment in which the litter was de-caked prior to windrowing, windrowed, turned in on itself on d 4, and then allowed to sit for 5 d (Turned), and 4) a treatment in which litter was de-caked prior to windrowing, windrowed, covered with 1.2 mm thick plastic, and allowed to sit for 9 d (Covered). There were 2 rows of plots, with 8 plots on either side. Thirty-three-and-a-half meters of space were not utilized on either the evaporative cool cell or exhaust fan ends of the house (not drawn to scale). Within the broiler house, the litter consisted of built-up litter that had been previously used by 9 consecutive flocks with the grow-out periods lasting 63 days. The litter profile was 10 to 13 cm deep. There were no previous disease or pathogen concerns associated with the litter in the house. As well, windrowing and chemical amendments were applied previously to the litter. The litter was windrowed every other flock and chemical amendments were applied if necessary between flocks. Low-pressure Sprinkler System During the previous grow-out period, before the onset of this study, the broiler house used a commercial low-pressure sprinkler system (Weeden Sprinkler System) [18]. The system involves low-pressure sprinkler nozzles, which are comparable to normal yard sprinklers with a spinner head. The sprinklers were mounted from the ceiling and ran the length of the house on 2 lines located 3 m from each sidewall with 20 sprinkler nozzles on either line for a total of 40 nozzles. Each nozzle had an output of 15 mL of water per s over an area of 42 m2 [18]. The sprinklers became active when the birds reached 5 wk of age. The Weeden controller utilized a 3-stage program that operated specifically on time intervals. The first stage began when the broilers reached 5 wk of age. The 3 set stages in the sprinkler controller were named stages 1, 2, and 3. Stage 1 was set to run every 30 min, stage 2 was set to run every15 min, and stage 3 was set to run every 5 minutes. At each stage, the system ran for only 20 s between each time interval. The temperature increment between each stage was set for 2.8°C, while the cool-cell system ran 1.7°C above the sprinkler. In 2014, from July 24 to September 25, the low-pressure sprinkler system utilized 80,962 liters of water, while the evaporative cooling pad utilized 133,281 liters. Treatments Each of the 4 treatments was randomly assigned to one of the 4 blocks creating 16 plots. There was a total of 4 replications for each treatment. The treatments consisted of a non-windrowed control, a static windrow, a turned windrow, and a covered windrow. The control was de-caked on d 0 and had no windrow application applied to it. The static treatment was de-caked, windrowed, and then allowed to sit for the following 9 days. The turned treatment was de-caked, windrowed, turned in on itself on d 4, and then allowed to sit for an additional 5 days. The covered treatment was de-caked, windrowed, covered with 1.2 mm thick plastic, and then allowed to sit for 9 days. The individual windrows, when formed, were 6 m long x 1.5 m wide x 1 m high in depth. Windrows were formed using a tractor equipped with a litter windrow blade [19]. On d 4, turned windrows were turned in on themselves using a skid steer loader. On d 9, all windrows were broken down in their respective plots. The house was then closed for 4 additional d (d 13) until day-old chicks were placed back in the house for the next commercial grow-out. No analysis was performed on placed chicks. Chicks were supplied feed and water ad libitum. Chicks used in this experiment were treated in compliance with the Guide for the Care and Use of Agricultural Animals in Research and Teaching [20]. Sample Collection On day 0, the previous flock was transported for processing. Litter samples were collected on d 4, when the turned treatment was being rolled in on itself; d 9, when all windrows were leveled out; d 13, when the next flock's chicks were placed; and d 20, 7 d after chick placement. Handfuls of litter were collected (at least 20 g) from 5 random locations at varying depths within each plot and then pooled into a Ziploc bag [21]. There were 16 total bags of litter for each d of litter collection. At the lab, 200 g of litter were transferred to smaller Whirl-Pak bags to be analyzed for N, P, and K [22]. Particle Size Particle size of the litter was determined using a Ro-Tap Sieve Shaker [23]. In duplicate, 100 g of litter were weighed and then placed into the first set of sieves (No. 4, 6, 8, 10, 16, 20, and 40). The first set of sieves was allowed to sift for 5 minutes. Upon completion, the litter that was able to sift to the bottom pan was placed on the top of a second set of sieves (No. 50, 70, 100, 140, 200, and 270). The second set of sieves was set in the Ro-Tap and allowed to sift for another 5 minutes. Each sieve was weighed, and then the following equation was used [24]:   \begin{equation*} {{\rm{d}}_{{\rm{gw}}}}{\rm{ = lo}}{{\rm{g}}^{ - 1}}\left[ {\frac{{\sum\nolimits_{{\rm{i = 1}}}^{\rm{n}} {\left( {{{\rm{W}}_{\rm{i}}}\log {{{\rm{\bar d}}}_{\rm{i}}}} \right)} }}{{\sum\nolimits_{{\rm{i = 1}}}^{\rm{n}} {{{\rm{W}}_{\rm{i}}}} }}} \right] \end{equation*} Where: dgw is geometric mean diameter or median size of particles by mass (mm), di is normal sieve aperture size of the ith sieve (mm), Wi is the mass on the ith sieve (g), and n is the number of sieves +1 (pan). Litter Moisture Litter moisture was measured in duplicate for each plot. Each individual litter sample was measured into 15 g samples. The wet weight of the sample was obtained before being placed into a drying oven [25]. Each sample was then placed in a 0.325 m2 drying oven for 24 h at 105°C. Once 24 h had passed, the samples were removed from the drying oven and weighed to determine their dry weight. Moisture content was calculated using the following equation [26]:   \begin{equation*} {\rm{MC}}(\% ) = \frac{{{{\rm{W}}_{{\rm{wet}}}} - {{\rm{W}}_{{\rm{dry}}}}}}{{{{\rm{W}}_{{\rm{wet}}}}}} \times 100 \end{equation*} Where: MC (%) is the percentage of moisture present or moisture content, Wwet is the wet weight, and Wdry is the dry weight. Nitrogen, Phosphoric Acid, and Potash All samples were analyzed by the Mississippi State Chemistry Lab. Phosphoric acid and potash were analyzed by AOAC methods 2006.03a and 2006.03, respectively [27, 28]. Nitrogen was analyzed by the DUMAS method utilizing the Rapid N Cube [29]. NH3 Ammonia generation for the litter was measured on d 9, 13, and 20. Measurements were not recorded on d 4 due to the windrows still in formation. Ammonia production off the litter at floor level was analyzed using an infrared photoaccoustic multi-gas analyzer with a dynamic flux chamber, using the design by Woodbury et al. [30, 31]. NH3 was calculated based on the chamber footprint, sampling time, and the mass of NH3 in the acid trap [30]. The NH3 gas being emitted off the litter was sampled for approximately 10 min to allow the infrared photoaccoustic multi-gas analyzer to calibrate. Ammonia levels were then recorded at 11, 12, and 13 minutes. The 3 readings were then averaged to determine NH3 production. pH Litter pH was analyzed by measuring 10 g of each litter sample in duplicate and then transferring each sample to a 500 mL beaker. Ultra purified water (100 mL) was then added to the beaker containing the 10 g of litter and stirred for approximately 5 min [25]. Using an Accumet Excel XL60 probe [32], the litter-water mixture was tested to obtain a pH reading [33]. Temperature Thermochron i-Button temperature sensors were used to record temperature throughout the house [34]. There were 2 sensors in each plot, both attached to a wooden stake that had one sensor submerged in the litter and the other sensor just below the litter surface. The sensor that was submerged in the litter recorded the temperature at the core of the windrow. The other sensor that was just below the litter's surface recorded the periphery temperature of the windrow. For all treatments, except the control, the periphery sensor was submerged 5.1 cm under the litter surface of the windrow. The control treatment's core sensor was 5.1 cm under the litter surface, while the periphery sensor was just below the surface. The sensors recorded the temperature every 20 min during the experiment, in accordance with their programming. In this experiment, the temperature data collected up to d 9 were used. Temperature data for the outside environment for Mississippi State University (33.4691°, −88.7822°) were collected from the National Climatic Data Center database for the entirety of this project (Table 1) [35]. The temperature of the house during the first 7 d of chick placement was recorded using a Rotem controller and is also displayed in Table 1 [36]. Table 1. Outside ambient temperature from d 1 to d 20 (September 25, 2014 to October 15, 2014). All data retrie- ved from Mississippi State University station, NCDC (33.4691° to 88.7822°). Average inside temperatures were obtained from the Rotem Platinum Plus controller protocol set in accordance with industry standards. Day  Outside temperature  Inside temperature    Max°C  Low°C  Average°C  0  28  14  26  1  29  15  41  2  29  17  44  3  28  17  45  4  28  18  44  5  31  17  43  6  31  16  42  7  32  17  41  8  28  19  38  9  27  9  29  10  21  9  –  11  26  12  –  12  27  17  –  13  31  19  32  14  31  18  32  15  32  19  32  16  31  19  32  17  31  19  32  18  28  21  32  19  29  14  32  20  20  11  30  Day  Outside temperature  Inside temperature    Max°C  Low°C  Average°C  0  28  14  26  1  29  15  41  2  29  17  44  3  28  17  45  4  28  18  44  5  31  17  43  6  31  16  42  7  32  17  41  8  28  19  38  9  27  9  29  10  21  9  –  11  26  12  –  12  27  17  –  13  31  19  32  14  31  18  32  15  32  19  32  16  31  19  32  17  31  19  32  18  28  21  32  19  29  14  32  20  20  11  30  View Large Statistical Analysis All data were analyzed using a randomized complete block design with a split plot over days. The means were separated using Fisher's protected LSD and were considered significant at P ≤ 0.05 [37, 38]. RESULTS AND DISCUSSION A delicate balance exists between improving litter quality and pathogen reduction in poultry litter. This balance is highly dependent on the moisture content of the litter. Litter quality is determined on the basis of the poultry litter's particle size, nitrogen retention, ammonia volatilization, levels of phosphorus and potassium, and pH. Pathogen reduction is obtained through high temperatures. High moisture inclusion will allow the litter to obtain optimal temperatures for pathogen reduction; however, litter quality may experience detrimental effects to overall quality due to the high moisture. Because there is such a thin line concerning moisture content, it is advantageous to utilize a strategy that balances both litter quality and pathogen reduction. The results from the current windrowing experiment in which low-pressure sprinklers were utilized demonstrated no difference in particle size (PS) among d or treatments (P = 0.9226; P = 0.0645; data not shown). Therefore, PS was determined not to be a concern for windrowing, as previous studies also have shown. Keener et al. [39] demonstrated that PS was not an issue if moisture was ≤45% at the start of windrowing and “mechanical mixing” was utilized during or at the end of the windrowing process. In the current study, litter moisture was ≤45% at the beginning of windrowing, and at the end, all treatments were mechanically mixed with a skid steer loader. Although there was not a significant difference for PS, there were differences for moisture content, N, NH3, P, K, and pH. The amount of moisture present in poultry litter can affect NH3 volatilization and microbial growth. Moisture is necessary to produce a windrow that reduces pathogens effectively because the elevated windrow temperature needed to inactivate bacteria is directly influenced by moisture content [8]. As stated previously, 50°C has been seen to reduce, inactivate, or destroy most of the major concerns in litter, such as pathogens, viruses, and parasite eggs [10, 11]. The average moisture content of litter in Mississippi is 24.8%, yet the recommended moisture content for an effective windrow is between 32 and 35% [5, 7]. Due to the use of a low-pressure sprinkler system in the latter wk of broiler rearing, a moisture content above Mississippi's average litter moisture was expected. Even though the sprinklers use a controlled amount of water that creates a wind-chill effect on the birds, some of the sprinkled water also may reach the litter. Therefore, correct management is critical to maintaining proper litter conditions. In this study, the moisture content for all treatments was above 40% at d 4; however, by d 20, the moisture content of litter for all treatments either met or fell below the recommended level of 32% (Figure 2). For the covered treatment, d 4 demonstrated the highest moisture content (60%) compared to all other treatments. However, by d 20 the moisture content of the covered treatment was reduced to 24%, the lowest moisture content of any treatment. The high moisture content for the covered treatment on d 4 is most likely due to the impermeable tarp being placed over the windrow, preventing moisture from evaporating into the air. After the tarp was removed on d 9, the moisture was then able to evaporate and revert to below recommended levels. Only the turned treatment remained at the recommended level of 32% on d 20. For all treatments, we expected the litter to dry out from d 13 to d 20. This is due to the fact that chicks were placed back into the house and ventilation and brooding were required. Overall, the litter moisture content was not in the effective range for windrowing from d 4 to d 9, as it was well above the recommended level. This high-moisture content present in the litter had the potential to increase the quantity of pathogens present in the litter, especially if the windrows did not reach the recommended temperatures for reducing pathogens [40]. Along with a possible increase in pathogens, a higher moisture content in the litter also could result in higher nitrogen loss, ammonia volatilization, and further degradation of litter [8, 41]. Figure 2. View largeDownload slide Treatment by d interaction for percent litter moisture (moisture %). The column consisting of the diagonal lines representsthe static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-e) are significantly different (P = 0.04; SEM = 3.39; N = 4). Figure 2. View largeDownload slide Treatment by d interaction for percent litter moisture (moisture %). The column consisting of the diagonal lines representsthe static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-e) are significantly different (P = 0.04; SEM = 3.39; N = 4). The results of this study indicated that the static 9 d windrow had the highest nitrogen concentration (4.60%) when compared to all other windrow treatments ((P = 0.02); Figure 3). However, all treatments were still below the recommended N level of 5 to 7% [42]. No differences among the control, covered, or turned treatments were determined. N loss usually occurs more in composted manure because of the higher rate of denitrification, which was not discovered among the treatments in this study, as the static treatment had the highest N concentration [43]. However, according to Mahimairaja et al. [43], denitrification occurs under anaerobic conditions, and nitrogen is lost in the form on N2. Therefore, it was expected that the covered treatment would have the greatest loss of N, because a 1.2 mm thick plastic tarp, which should have prevented aerobic conditions, covered the windrow. The plastic also did not allow for the evaporation of moisture from the surface of the windrow, providing an environment more suitable for denitrification. However, it was concluded that the covered, turned, and control treatments were not different in terms of loss of N. Figure 3. View largeDownload slide N levels for all sample plots within a treatment were averaged together to attain the mean N content (%) for each treatment. The column consisting of the diagonal lines represents the static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-b) are significantly different (P = 0.02; SEM = 0.04; N = 16). Figure 3. View largeDownload slide N levels for all sample plots within a treatment were averaged together to attain the mean N content (%) for each treatment. The column consisting of the diagonal lines represents the static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-b) are significantly different (P = 0.02; SEM = 0.04; N = 16). Although N was not different among the covered, turned, or control treatments, all 3 were different when compared to the static treatment but not by an alarming amount (<0.21%). Flory et al. [44] demonstrated the effectiveness of turned windrows in a commercial setting vs. a control. Their results determined that there were no differences in nutrient value or N level among treatments; however, a numerical decrease in N level was apparent among treatments. In the current study, the higher N content demonstrated for the static treatment may be the result of the high temperatures the treatment obtained in its core and periphery. Lavergne et al. [4] demonstrated a correlation between total N and the maximum temperature after the addition of water in static in-house windrows. The results indicated that a windrow that reached a higher temperature had a higher N content than a windrow that had an average temperature [4]. Because the static treatment in our study had one of the highest temperatures among all other treatments, it can be suggested that the elevated N may have been a result of the high temperature. Another reason for the loss of nitrogen during windrowing is ammonia volatilization. Henry and White [41] discovered that a large quantity of N lost during windrowing was due to ammonia volatilization. In the current study, no differences among treatments were found for NH3 production (data not shown). This finding was surprising because poultry manure typically contains 5 to 7% total N, with 60 to 75% of the N in the form of uric acid [42, 45], and when uric acid breaks down, it produces NH3 [46]. Keener et al. [39] reported a reduction in N loss through NH3 volatilization when windrows were covered. Therefore, lower NH3 generation was expected from the static and turned windrow treatments in the current study when compared to our covered treatment. Although there were no differences found for NH3 production among treatments, this result may have been influenced by the high initial moisture contents, which also could have led to the findings for N content. Because NH3 volatilization is one of the major pathways for N loss, it is important to monitor NH3 production over time. However, the monitoring of NH3 production is important for more than just N loss, NH3 production is also a major welfare concern [45]. Over the course of this study, the concentration of NH3 generated directly off the litter was determined to decrease (d 9, 684.67 ppm; d 13, 585.96 ppm; and d 20, 111.96 ppm) (Figure 4). The high NH3 generation at d 9 and 13 may be the result of the high litter moisture created by the low-pressure sprinkler system in concurrence with the evaporative cooling system. As mentioned before, uric acid is less likely to degrade into NH3 if the litter is kept dry [46]. Even as the level of NH3 produced decreased, on d 13 the NH3 concentration being generated by the litter was well above a safe level for day-old chicks. On d 20, the NH3 being generated by the litter into the flux chamber was reduced to 111.96 ppm. The reduction in NH3 production from d 13 to d 20 was most likely the direct result of ventilation and the use of the brooders, as it would dry the litter and therefore reduce NH3 generated by the litter. It is important to note that in this study, the NH3 monitored was that generated directly by the litter into the flux chamber and not the air surrounding the chicks. Due to the ventilation protocol in place in the broiler house, no chicks were under conditions in which the atmospheric NH3 in the house exceeded 25 ppm, the maximum limit for atmospheric ammonia at bird height [47]. Figure 4. View largeDownload slide Ammonia levels of all plots were averaged together for each sampling d to get the mean NH3 levels (ppm) for each day. The light gray column represents the mean NH3 of all plots on d 9. The dark gray column represents the mean NH3 for all plots on d 13. The white column represents the mean NH3 for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.0002; SEM = 56.90; N = 16). Figure 4. View largeDownload slide Ammonia levels of all plots were averaged together for each sampling d to get the mean NH3 levels (ppm) for each day. The light gray column represents the mean NH3 of all plots on d 9. The dark gray column represents the mean NH3 for all plots on d 13. The white column represents the mean NH3 for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.0002; SEM = 56.90; N = 16). In the current study it also was determined that potash and phosphoric acid concentrations increased over time (Figures 5 and 6). Potash increased over a 20-day period at 3.98, 3.93, 4.19, and 4.08% on d 4, 9, 13, and 20, respectively. Phosphoric acid increased over a 20-day period at 5.49, 5.63, 6.07, and 6.12% on d 4, 9, 13, and 20, respectively. It is important to note that an increase in the concentration of P in litter is not a favorable outcome for litter quality. If there is too much P in the litter, then when applied as fertilizer, the high P concentrations could run off into nearby streams, estuaries, or lakes. N, P, and K are all needed for life; however, too much in the environment can cause eutrophication [48]. Eutrophication can result in an increase of algae and deoxygenation of the water, directly killing the ecosystem in that body of water [48, 49]. In this study, the treatments on d 20 had P2O5 and K2O levels of 6 and 4%, respectively. According to a study done by the University of Georgia Cooperative Extension, composted litter has 3 and 2.3% levels of P2O5 and K2O, respectively [50]. One possible explanation for the high level of P and K is the reuse of the litter over several flocks [4, 51]. A study that examined the trend of nutrient content in Mississippi, determined an increasing trend of nutrients until the 20th flock [51]. It also was noted that litter management that utilizes total clean-out will experience lower nutrient levels [51]. With the increasing concern for the environment and the ecosystem, the increase of both P and K is not a desirable outcome. Figure 5. View largeDownload slide Potash (K2O) content for all samples plots was averaged together for each sampling d to obtain the mean potash concentration (%) over a 20-day period. The black column represents the mean potash of all the plots on d 4. The light gray column represents the mean potash of all plots on d 9 when the windrows were broken down. The dark gray column represents the mean potash for all plots on d 13 when chicks were placed into the broiler house. The white column represents the mean potash for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.02; SEM = 0.06; N = 16). Figure 5. View largeDownload slide Potash (K2O) content for all samples plots was averaged together for each sampling d to obtain the mean potash concentration (%) over a 20-day period. The black column represents the mean potash of all the plots on d 4. The light gray column represents the mean potash of all plots on d 9 when the windrows were broken down. The dark gray column represents the mean potash for all plots on d 13 when chicks were placed into the broiler house. The white column represents the mean potash for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.02; SEM = 0.06; N = 16). Figure 6. View largeDownload slide Phosphoric acid (P2O5) levels for all plots were averaged together for each sampling d to obtain the mean phosphoric acid content (%) for each day. The black column represents the mean phosphoric acid of all the plots on d 4. The light gray column represents the mean potash of all plots on d 9. The dark gray column represents the mean potash for all plots on d 13. The white column represents the mean potash for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.0001; SEM = 0.10; N = 16). Figure 6. View largeDownload slide Phosphoric acid (P2O5) levels for all plots were averaged together for each sampling d to obtain the mean phosphoric acid content (%) for each day. The black column represents the mean phosphoric acid of all the plots on d 4. The light gray column represents the mean potash of all plots on d 9. The dark gray column represents the mean potash for all plots on d 13. The white column represents the mean potash for all plots on d 20. Columns without common superscripts (a-b) are considered significantly different (P = 0.0001; SEM = 0.10; N = 16). Liang et al. [8], while evaluating the effects of in-house broiler litter windrowing, noticed an increase in both total P and K in the windrow treatments that were under high-moisture conditions. It was deduced that the increase was relative to P, Ca, and K being the most reliable nutrients to show degradation; but it also was found that the control treatment had greater degradation than the windrow treatments [8]. However, it should also be mentioned that in that study, the control treatment had higher moisture (21.5%) than the highest moisture windrow treatment (19.6%) from the very beginning [8]. In respect to windrowing poultry litter after the utilization of low-pressure sprinkler systems in conjunction with an evaporative cooling system, higher P and K over time may be from the higher degradation occurring as a result of moisture and temperature, which is comparative to the study conducted by Liang et al. [8]. Litter moisture also can have an impact on litter pH. As % moisture is increased, the pH of the litter becomes more basic [52]. In reference to the average pH of poultry litter in Mississippi, which is 8.4, all treatments were in the average range except for the covered treatment on d 4 (8.75) [5]. The pH for the turned treatment was initially low and then increased by d 9 and 13 but reverted to a lower pH by d 20 (8.39, 8.48, 8.55, and 8.26 on d 4, 9, 13, and 20, respectively). Both the static and control windrows demonstrated an increase in pH on d 9, but the pH then decreased from d 13 thru d 20 (Figure 7). The static windrow treatment started at a pH of 8.36 on d 4, increased to 8.43 on d 9, and then decreased to 8.38 and 8.06 on d 13 and 20, respectively. The pH for the control treatment increased from 8.40 on d 4 to 8.59 on d 9, but then decreased to 8.48 and 8.16 on d 13 and 20, respectively. For the covered windrow treatment, pH was initially high but over time decreased (8.75, 8.67, 8.36, and 8.02 on d 4, 9, 13, and 20, respectively). However, none of the windrowing treatments or the control treatment reduced the pH to a level that would improve litter quality. If the pH could have been reduced below 7.5, the NH3 concentration also may have been reduced [53]. According to Groot Koerkamp [45], a pH of 7 or below allows NH3 to be bound as ammonium, thus preventing NH3 volatilization. The more basic the pH is (above 5.5), the more readily uric acid is broken down [45]. A lower pH would have stunted NH3 production, substantially yielding more N retention in the litter. Therefore, the results of this study suggest that no windrowing technique improved litter quality when compared to the control treatment, which may be attributed to the higher moisture present at the onset of this study from the utilization of a low-pressure sprinkler system in tangent with an evaporative cooling system. Figure 7. View largeDownload slide Interaction between d and treatment for litter pH (pH). The column consisting of the diagonal lines represents the static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-h) are significantly different (P = 0.003; SEM = 0.70; N = 4). Figure 7. View largeDownload slide Interaction between d and treatment for litter pH (pH). The column consisting of the diagonal lines represents the static treatment, the column consisting of dots represents the control treatment, the column consisting of hatched lines represents the covered treatment, and the column consisting of horizontal lines represents the turned treatment. Columns without common superscripts (a-h) are significantly different (P = 0.003; SEM = 0.70; N = 4). Though the moisture, N, NH3, P, K, and pH results all indicated the treatments did not have a positive effect on litter quality, the temperature results may have impacted the litter environment in a positive manner. According to the EPA 503b rule, for a windrow to effectively reduce pathogens, it must exceed 40°C for 120 h and within the 120 h exceed 55°C for 4 h [14]. To further this rule, it has been recommended that the windrow exceed 50°C for at least 24 h [10]. Other studies, such as Barker et al. [13], Lavergne et al. [4], and Macklin et al. [9], have attempted to reach this benchmark but have been unable to obtain these temperatures in the periphery of the windrow. Additionally, previous research conducted by Schmidt et al. [54], utilizing a 42-point grid, established that the EPA 503b rule could be achieved only within approximately 38.4 ± 26.2% of a windrow. In the current study, both the periphery and core temperatures were monitored using a 2-point system. The static and covered treatments both met the criteria for the EPA 503b rule in the core and periphery (Figures 8 and 9). The turned treatment met the criteria for the EPA 503b rule only in its core (Figure 8). Although a 2-point method is not the most accurate procedure at predicting the entire windrow temperature, utilizing this method is still a valuable resource [9]. Because both the static and covered treatments were effective in reaching 40°C for 120 h, 50°C for 24 h, and 55°C for 4 h in their periphery and core, both treatments have the potential to reduce pathogens, diseases, and parasites present in the litter. Figure 8. View largeDownload slide Core temperatures for all samples were averaged together for each sampling d to attain the mean core temperature (°C) for each day. The black solid line (——) represents the turned treatment, the dotted line (······) represents the static treatment, the dash-dot line (-·-·-·-) represents the covered treatment, and the dashed line (− − −) represents the control treatment. Figure 8. View largeDownload slide Core temperatures for all samples were averaged together for each sampling d to attain the mean core temperature (°C) for each day. The black solid line (——) represents the turned treatment, the dotted line (······) represents the static treatment, the dash-dot line (-·-·-·-) represents the covered treatment, and the dashed line (− − −) represents the control treatment. Figure 9. View largeDownload slide Peripheral temperatures for all samples were averaged together for each sampling d to attain the mean peripheral temperature (°C). The black solid line (——) represents the turned treatment, the dotted line (······) represents the static treatment, the dash-dot line (-·-·-·-) represents the covered treatment, and the dashed line (− − −) represents the control treatment. Figure 9. View largeDownload slide Peripheral temperatures for all samples were averaged together for each sampling d to attain the mean peripheral temperature (°C). The black solid line (——) represents the turned treatment, the dotted line (······) represents the static treatment, the dash-dot line (-·-·-·-) represents the covered treatment, and the dashed line (− − −) represents the control treatment. It is evident from this study that the quality of the litter was affected by the inclusion of additional moisture through the utilization of a low-pressure sprinkler system during the grow-out period. Because of these effects, there were no improvements in N, NH3, P, K, and pH at the conclusion of the windrowing procedure. The temperature in the windrows, however, was increased to an effective range in order to reduce potential pathogens that may have been present in the litter. In future studies, it will be imperative to find a balance between moisture and temperature, so that both litter quality and pathogen reduction can be maximized. CONCLUSIONS AND APPLICATIONS The higher moisture content in the litter resulted in higher NH3 volatilization, a lower percentage of N, and higher P and K over time, after the utilization of in-house windrowing. The moisture content in the litter was above the recommended level of 32 to 35% at the onset of windrowing; however, by d 20, only the static treatment was within the recommended level, and all other treatments and control had been reduced to <30% moisture. Windrowing and management practices reduced the moisture to a safer level for the birds. The higher moisture content in the litter increased the ability of the static and covered treatments to reach the desired temperatures in both the core and surface of those treatments, which is favorable for reducing pathogens, according to the EPA 503b rule. The relatively high moisture present in the litter may be a result of the low-pressure sprinklers being utilized in conjunction with the evaporative cooling system. Further studies should be conducted to compare the effects of the low-pressure sprinklers being utilized alone vs. low-pressure sprinklers being utilized in tangent with evaporative cooling pads on in-house windrowing of poultry litter. Footnotes 1 This publication is a contribution of the Mississippi Agricultural and Forestry Experiment Station. Primary Audience: Flock Supervisors, Quality Assurance Personnel, Researchers REFERENCES AND NOTES 1. Shepherd E. M. 2010. Environmental Effects on Footpad Dermatitis. M.S. Thesis . Univ. Georgia, Athens. 2. Miller F. C. 1996. Composting of municipal solid waste and its components. Pages 115– 154 in Microbiology of solid waste . Palmisano A. C., Barlaz M. A., ed. CRC Press, Boca Raton, FL. 3. Malone B. 2008. Bedding alternatives and windrowing programs. Pages 32– 34 in Proc. Virginia Poult. Health Manage. Semin. , Roanoke, VA. 4. Lavergne T. K., Stephens M. F., Schellinger D., Carney Jr W. and A.. 2006. 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Journal of Applied Poultry ResearchOxford University Press

Published: Mar 1, 2018

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