How does red light affect layer production, fear, and stress?

How does red light affect layer production, fear, and stress? ABSTRACT Light-emitting diode (LED) light bulbs are becoming more prevalent in layer production as unlike CFLs they are dimmable and are even more energy-efficient than CFLs. There is also discussion on whether the spectrum of light that is produced by the bulb can affect production, stress, and behavior of laying hens. To investigate if differences between how the bulb that produce different wavelengths of light affect these factors, we raised White Leghorn hens under either a bulb that produced white light with the addition of red light (Once, Inc, AgriShift MLL; RED) or a bulb that produced only white light (Overdrive, L10NA19DIM 3000 K; WHITE). Each treatment consisted of 36 White Leghorn hens, and the experiment was replicated three times for a total of 108 hens per treatment. Production parameters including % hens in lay, feed conversion, average egg weight, total eggs per hen, eggshell breaking strength, and Haugh units were measured. Hen fear response during tonic immobility and inversion was documented at 3 time points during the study (18, 42, and 72 wk of age). Stress susceptibility was also quantified using plasma corticosterone, heterophil to lymphocyte ratio, and composite asymmetry score at the same time points as the fear testing. No production parameters were affected by lighting type (P > 0.05). Lighting type did not affect tonic immobility or inversion response (P > 0.05). By 42 wk of age and continuing on until 72 wk of age, the RED treatment had lower plasma corticosterone concentrations, lower heterophil to lymphocyte ratios, and lower composite asymmetry scores than the WHITE treatment (P < 0.05). The results indicate that including red light in the spectrum of light layers are reared under can lower stress susceptibility but had no effect on fear response or production parameters when compared to white light. INTRODUCTION The wavelength of light has been shown to affect behavior, welfare, and performance of the poultry (Manser, 1996; Rozenboim et al., 1999a; 1999b). Birds unlike mammals have retinal photoreceptors responsible for vision and extra-retinal photoreceptors responsible for detecting photoperiod and synchronizing their physiology to the environment (Kumar and Rani, 1999). The location of these photoreceptors are found in three main organs: the eye, pineal gland, and hypothalamus. The retina contains three photoreceptors: rods, cones, and double cones (Perry, 2004). The cones are responsible for color vision and are tetrachromatic in birds (Prescott and Wathes, 1999). Photoreceptive pigments within these cones have a maximum sensitivity to violet (415 nm), blue (455 nm), green (508 nm), or red (571 nm) (Yoshizawa, 1992; Perry, 2004). The pineal gland, which is first sensitive to light at 3 d into embryogenesis (Cooper et al., 2011), controls the secretion of serotonin and melatonin. These hormones are involved in control of circadian rhythm, endocrine functions, mobility, body temperature, and reproduction in poultry (Pelham et al., 1972; Baxter et al., 2014). It has been demonstrated that if white light intensity is under 4 lux it cannot penetrate the skull and reach the pineal gland that results in the repression of the secretion of serotonin and melatonin (Lewis and Morris, 2006). Furthermore, different wavelengths of light directly penetrate the hypothalamus, which cause different effects (Lewis and Morris, 2006). Long wavelength light directly penetrates into the skull and brain, and then reaches the hypothalamus (Baxter et al., 2014). Lights utilizing short wavelengths must be at higher intensities order to affect the hypothalamus (Benoit, 1964; Baxter et al., 2014). Extra-retinal photoreceptors have been found to be sensitive to the red wavelengths of the electromagnetic spectrum (Cedden and Göğer, 1999). Birds perceive light differently due to differences in spectral sensitivity and density of photoreceptive pigments found in their retinas (Prescott and Wathes, 1999). The perceived intensity is relative to the spectral power output of the light and the spectral sensitivity of the bird retina. Red light appears brighter to birds than blue light at lower intensities (Prayitno and Phillips, 1997). Furthermore, the retina can be stimulated with light at low intensities, but the extra-retinal photoreceptors require higher light intensities (Harrison and Becker, 1969). This results in lower wavelengths such as blue or green light requiring higher intensities than longer wavelengths such as red light to stimulate hypothalamic photoreceptors (Pang et al., 1974). The retina of birds has a peak sensitivity to yellow and green wavelengths; however, birds exposed to green light have a delay in the rate of sexual maturity, lower egg production, and lower levels of steroids and GnRH-I mRNA expression (Siopes and Wilson, 1980; Mobarkey et al., 2010; Gongruttananun, 2011; Mobarkey et al., 2013; Baxter et al., 2014). Therefore, if only the retina is stimulated by the green light it will inhibit reproduction (Siopes and Wilson, 1980; Mobarkey et al., 2010; Gongruttananun, 2011; Mobarkey et al., 2013). Conversely, exposure to higher wavelengths has been demonstrated to increase egg production and resulted in higher steroid and gonadotropin concentrations and higher neuropeptide mRNA expression (Foss et al., 1972; Reddy et al., 2012; Hassan et al., 2013; Huber-Eicher et al., 2013; Baxter et al., 2014). Previous studies have shown that laying hens reared under monochromatic red light had higher egg production than those reared under white, green (Pyrzak et al., 1987; Huber-Eicher et al., 2013; Baxter et al., 2014; Svobodova et al.,2015), and blue light-emitting diode (LED) light (Hassan et al., 2013). Borille et al. (2013) found that birds reared under white light produced more eggs than those reared under red light. Li et al. (2014) found that birds reared under red and white light had the heaviest egg, whereas those reared under blue and green light had the lightest eggs. However, egg shell strength was higher in birds reared under green light than those reared under white and blue light (Li et al., 2014). Behavior and stress have also been demonstrated to be affected by light wavelength. Birds have been shown to spend more time sitting or standing under short wavelengths (blue/green) and exhibited more locomotion under longer (red/yellow) wavelengths (Sultana et al., 2013). Birds reared under red/yellow light exhibit tonic immobility for longer periods of time, indicating that they were more fearful than the short-wavelength exposed birds (Sultana et al., 2013). Green light has been demonstrated to reduce time spent feeding (Huber-Eicher et al., 2013). D’Eath and Stone (1999) found that birds reared under red light had lowered social recognition. Archer and Byrd (unpublished data) observed that birds reared with a high level red light had lower stress susceptibility, as indicated by corticosterone, composite asymmetry, and humoral immunity) than those reared under white light or light with a high level of blue light. Svobodova et al. (2015) observed that the lowest mortality rate was 12.65% for the laying hens reared under the red light, whereas the highest mortality was 14.30% for the hens raised under the blue light possibly indicating less stress susceptibility in birds reared under red light. The objective of this study was to determine how two different commercially available LED lights affected laying hen production, fear, and stress. The first light was a warm white LED fixture and the second was a white LED fixture that contained monochromatic red light. Hens were reared under the these lights for an entire lay cycle and it was hypothesized that the addition of red light would increase production and lower fear and stress responses. MATERIALS AND METHODS Animals and Husbandry A total of 216 White Leghorn hens were used in this experiment. Birds were housed starting at 17 wk of age and until the end of the study (72 wk of age) in a two-level A-frame cage system in groups of three hens per cage. Cages measured (520.7 mm deep × 412.8 mm wide × 393.7 mm high). The hens were housed in three rooms that were kept at a consistent temperature of 70°F, and the light schedule had 16 h of light to 8 h of darkness with an average illumination of 40 lux at the feeder height as measured with a light meter (MK350, UPRTek, Jhunan Taiwan). Half of the birds were housed under LED light bulbs which had white and red LEDs (Once, AgriShift® MLM-Red; Red), whereas the other half were housed under LED light bulbs that where only white (Overdrive, L10NA19DIM 3000 K; White). The spectrum of each light type is presented in Figure 1 as measured with a light meter (MK350, UPRTek, Jhunan Taiwan). Each of the three rooms was split down the middle with a light-proof barrier but allowed for the air space to be shared by both treatments. Each room contained both treatments with one on each side of the barrier with each room having 12 replicate cages per treatment. The birds were managed according to the guidelines set forth in the Guide for the Care and Use of Agricultural Animals in Research and Teaching (FASS, 2010) and all procedures were approved by the Texas A&M University animal care committee (IACUC #2015-0235). Figure 1. View largeDownload slide Spectrum of the lighting treatments used in this study. Figure 1. View largeDownload slide Spectrum of the lighting treatments used in this study. Production Measurements Bird performance was evaluated through daily measurements of egg production and egg weight. The former was used to calculate flock production by determining the percentage of the flock that was in lay from day to day; the latter allowed for the calculation of the flock's feed conversion rate. Measurements of feed consumption and feed conversion were calculated monthly based on the weight of the eggs produced and the weight of the feed given to the birds throughout each month. On a biweekly basis, eggs were collected from each cage and analyzed for egg quality measurements including: Haugh unit and shell breaking strength. Haugh units were determined using an automatic scale and albumen-height gage (2/A, Futura, Lohne Germany). Breaking strength was measured using the QC-SPA System (Technical Services and Supplies, York, England). Fear Measurements Tonic immobility and inversion tests to measure fear responses. Both fear tests were conducted at 18, 42, and 72 wk of age within treatment rooms. Tonic immobility testing was carried out as described by Archer and Mench (2014) on all birds. In brief, birds were placed on their backs in a cradle and held there for 15 s. If the bird righted before 10 s, tonic immobility was re-induced up to 3 times. If the bird could not be induced in 3 attempts, it was scored as 0. Latency to right and number of induction attempts was recorded. The test was terminated in 600 s if a bird failed to right and that bird was scored as 600. Longer latency to right indicates greater level of fear. All birds were also subjected to an inversion test, as described by Newberry and Blair (1993) and Archer and Mench (2014). Each bird was removed from its cage and then inverted it by holding it by its legs with one hand until the bird ceased to wing flap, or for 30 s. We determined the duration of and number of wing flaps (Cannon, ZR900, Melville, NY, USA; 24 frames/s). Intensity of flapping was then calculated with greater intensity indicates greater level of fear. Stress Measures At 18, 42, and 72 wk age blood samples were collected from 12 birds per treatment per room. Blood sampling occurred several days after fear testing and took less than 1 min. Between 1 and 2 mL of blood were collected using syringes from wing vein of each bird, and a drop was used to prepare a blood-smear slide. The remaining blood was injected into a plasma separation gel and lithium heparin vaccutainer (BD 368056, BD, Franklin Lakes, NJ), which was temporarily stored in an ice bath. Once all samples had been taken, the vaccutainers were spun down in a Beckman GS-6R centrifuge (Beckman Coulter, Brea, CA) for 15 min at 4,000 RPM to separate the cells from the plasma. The plasma was poured into 2 mL microcentrifuge tubes and stored at −19°C until further analysis. The blood-smear slides were stained using a hematology staining kit (Cat# 25034, Polysciences Inc, Warrington, PA). Plasma corticosterone concentrations were measured using a commercially available ELISA kit (Enzo Life Sciences, ADI-901-097, Farmingdale, NY). The inter and intra-assay %CV were both under 5%. Higher plasma corticosterone concentrations indicate greater stress susceptibility. The heterophil/lymphocyte ratio was measured by taking the blood smear slides prepared earlier and observing them under 1,000X magnification (10X eyepiece and 100X oil emersion lens) using an Omax DCE-2 microscope (Kent, WA). The numbers of both heterophils and lymphocytes observed were counted until the total observed number reached 100. A keystroke counter was used to accurately keep track of the number of cells observed. Greater ratios indicate greater stress susceptibility. Physical asymmetry of all birds was also measured at each time point, following the protocol outlined in Archer and Mench (2013). Using a calibrated Craftsman IP54 Digital Caliper (Sears Holdings, Hoffman Estates, IL), the middle toe length, metatarsal length, and metatarsal width were measured for both the right and left legs. All measurements were done by one individual. The composite asymmetry score was calculated by taking the sum of the absolute value of left minus right of each trait, and then dividing by the total number of traits. Thus, the formula for this trial would be (∣L−R∣MTL+∣L−R∣ML+∣L−R∣MW)/3 = composite asymmetry score. Greater composite asymmetry score indicates greater stress susceptibility. Statistical Analysis To investigate the data, the GLM procedure was used with treatment, testing period, and the interaction of the two as factors. Room/experimental replication was not found to be significant so data were combined. Pen nested within treatment was the error term used to test for treatment effects. The least significant difference test was used to test all planned comparisons. All of the assumptions were tested (Shapiro–Wilk test for normality, Levene's test for homogeneity of variance). No transformations were needed to meet assumptions. All analyses were performed using SAS 9.3 for Windows (SAS Institute Inc.). Significant differences were at P < 0.05. RESULTS Production The production data are presented in Table 1. Lighting treatment did not affect egg shell breaking strength, Haugh units, % of hens in lay, feed conversion, average egg weight, or total eggs produced per bird (P > 0.05). There was also no interaction between lighting treatment and lay period in any of the production parameters measured (P > 0.05). All production parameters measured differed from the 18 to 42 wk period when compared to the 42 to 72 wk period (P < 0.05). Table 1. Egg quality and production of layers reared under two different spectrums of LED light. Treatment Breaking strength (g) Haugh units % Hens in lay Feed conversion (g of feed per g of egg) Average egg weight (g) Total eggs/bird 18 to 42 wk of age Red 3200.2 105.9 93.4 1.92 56.8 137.2 White 3255.8 105.6 91.4 1.91 56.6 134.4 SEM 21.0 0.1 0.7 0.03 0.2 1.4 42 to 72 wk of age Red 3427.0 90.7 81.9 1.72 62.0 177.8 White 3515.0 89.9 80.3 1.71 61.9 174.2 SEM 29.7 0.3 0.9 0.02 0.2 2.5 Overall Red 3320.5 98.2 86.5 1.80 59.7 315.0 White 3389.9 97.7 84.8 1.79 59.5 308.5 SEM 22.5 0.2 0.8 0.02 0.2 3.7 Period 18 to 42 wk 3228a 105.8a 91.4a 1.92a 56.7a 134.4a 42 to 72 wk 3471b 90.3b 80.3b 1.71b 62.0b 174.2b SEM 20.8 0.7 0.8 0.03 0.3 6.2 Treatment F1,143 = 3.75, P = 0.06 F1,143 = 1.93, P = 0.17 F1,143 = 2.19, P = 0.14 F1,23 = 0.00, P = 0.98 F1,143 = 0.27, P = 0.61 F1,23 = 0.30, P = 0.59 Period F1,143 = 46.05, P < 0.001 F1,143 = 1670.35, P < 0.001 F1,143 = 84.98, P < 0.001 F1,23 = 32.91, P = 0.001 F1,143 = 320.89, P < 0.001 F1,23 = 377.86, P < 0.001 Interaction F1,143 = 0.26, P = 0.61 F1,143 = 0.60, P = 0.44 F1,143 = 0.01, P = 0.91 F1,23 = 0.01, P = 0.93 F1,143 = 0.04, P = 0.84 F1,23 = 0.13, P = 0.73 Treatment Breaking strength (g) Haugh units % Hens in lay Feed conversion (g of feed per g of egg) Average egg weight (g) Total eggs/bird 18 to 42 wk of age Red 3200.2 105.9 93.4 1.92 56.8 137.2 White 3255.8 105.6 91.4 1.91 56.6 134.4 SEM 21.0 0.1 0.7 0.03 0.2 1.4 42 to 72 wk of age Red 3427.0 90.7 81.9 1.72 62.0 177.8 White 3515.0 89.9 80.3 1.71 61.9 174.2 SEM 29.7 0.3 0.9 0.02 0.2 2.5 Overall Red 3320.5 98.2 86.5 1.80 59.7 315.0 White 3389.9 97.7 84.8 1.79 59.5 308.5 SEM 22.5 0.2 0.8 0.02 0.2 3.7 Period 18 to 42 wk 3228a 105.8a 91.4a 1.92a 56.7a 134.4a 42 to 72 wk 3471b 90.3b 80.3b 1.71b 62.0b 174.2b SEM 20.8 0.7 0.8 0.03 0.3 6.2 Treatment F1,143 = 3.75, P = 0.06 F1,143 = 1.93, P = 0.17 F1,143 = 2.19, P = 0.14 F1,23 = 0.00, P = 0.98 F1,143 = 0.27, P = 0.61 F1,23 = 0.30, P = 0.59 Period F1,143 = 46.05, P < 0.001 F1,143 = 1670.35, P < 0.001 F1,143 = 84.98, P < 0.001 F1,23 = 32.91, P = 0.001 F1,143 = 320.89, P < 0.001 F1,23 = 377.86, P < 0.001 Interaction F1,143 = 0.26, P = 0.61 F1,143 = 0.60, P = 0.44 F1,143 = 0.01, P = 0.91 F1,23 = 0.01, P = 0.93 F1,143 = 0.04, P = 0.84 F1,23 = 0.13, P = 0.73 a,bSuperscripts within column and time point indicate significant differences P < 0.05. View Large Table 1. Egg quality and production of layers reared under two different spectrums of LED light. Treatment Breaking strength (g) Haugh units % Hens in lay Feed conversion (g of feed per g of egg) Average egg weight (g) Total eggs/bird 18 to 42 wk of age Red 3200.2 105.9 93.4 1.92 56.8 137.2 White 3255.8 105.6 91.4 1.91 56.6 134.4 SEM 21.0 0.1 0.7 0.03 0.2 1.4 42 to 72 wk of age Red 3427.0 90.7 81.9 1.72 62.0 177.8 White 3515.0 89.9 80.3 1.71 61.9 174.2 SEM 29.7 0.3 0.9 0.02 0.2 2.5 Overall Red 3320.5 98.2 86.5 1.80 59.7 315.0 White 3389.9 97.7 84.8 1.79 59.5 308.5 SEM 22.5 0.2 0.8 0.02 0.2 3.7 Period 18 to 42 wk 3228a 105.8a 91.4a 1.92a 56.7a 134.4a 42 to 72 wk 3471b 90.3b 80.3b 1.71b 62.0b 174.2b SEM 20.8 0.7 0.8 0.03 0.3 6.2 Treatment F1,143 = 3.75, P = 0.06 F1,143 = 1.93, P = 0.17 F1,143 = 2.19, P = 0.14 F1,23 = 0.00, P = 0.98 F1,143 = 0.27, P = 0.61 F1,23 = 0.30, P = 0.59 Period F1,143 = 46.05, P < 0.001 F1,143 = 1670.35, P < 0.001 F1,143 = 84.98, P < 0.001 F1,23 = 32.91, P = 0.001 F1,143 = 320.89, P < 0.001 F1,23 = 377.86, P < 0.001 Interaction F1,143 = 0.26, P = 0.61 F1,143 = 0.60, P = 0.44 F1,143 = 0.01, P = 0.91 F1,23 = 0.01, P = 0.93 F1,143 = 0.04, P = 0.84 F1,23 = 0.13, P = 0.73 Treatment Breaking strength (g) Haugh units % Hens in lay Feed conversion (g of feed per g of egg) Average egg weight (g) Total eggs/bird 18 to 42 wk of age Red 3200.2 105.9 93.4 1.92 56.8 137.2 White 3255.8 105.6 91.4 1.91 56.6 134.4 SEM 21.0 0.1 0.7 0.03 0.2 1.4 42 to 72 wk of age Red 3427.0 90.7 81.9 1.72 62.0 177.8 White 3515.0 89.9 80.3 1.71 61.9 174.2 SEM 29.7 0.3 0.9 0.02 0.2 2.5 Overall Red 3320.5 98.2 86.5 1.80 59.7 315.0 White 3389.9 97.7 84.8 1.79 59.5 308.5 SEM 22.5 0.2 0.8 0.02 0.2 3.7 Period 18 to 42 wk 3228a 105.8a 91.4a 1.92a 56.7a 134.4a 42 to 72 wk 3471b 90.3b 80.3b 1.71b 62.0b 174.2b SEM 20.8 0.7 0.8 0.03 0.3 6.2 Treatment F1,143 = 3.75, P = 0.06 F1,143 = 1.93, P = 0.17 F1,143 = 2.19, P = 0.14 F1,23 = 0.00, P = 0.98 F1,143 = 0.27, P = 0.61 F1,23 = 0.30, P = 0.59 Period F1,143 = 46.05, P < 0.001 F1,143 = 1670.35, P < 0.001 F1,143 = 84.98, P < 0.001 F1,23 = 32.91, P = 0.001 F1,143 = 320.89, P < 0.001 F1,23 = 377.86, P < 0.001 Interaction F1,143 = 0.26, P = 0.61 F1,143 = 0.60, P = 0.44 F1,143 = 0.01, P = 0.91 F1,23 = 0.01, P = 0.93 F1,143 = 0.04, P = 0.84 F1,23 = 0.13, P = 0.73 a,bSuperscripts within column and time point indicate significant differences P < 0.05. View Large Fear and Stress Fear and stress response data are presented in Table 2. There was no effect of lighting treatment (P > 0.05) or interaction of lighting treatment and age (P > 0.05) on latency to right during TI testing or in flapping intensity during inversion testing. Differences in latency to right and flapping intensity were observed between the different testing ages (P > 0.05). The layers overall had shorter latency to right (275.2 s) and less intense flapping (4.76 flaps/s) at 42 wk of age when compared to 18 (294.5 s and 5.60 flaps/s) and 72 (342.7 s and 5.34 flaps/s) weeks of age. Table 2. Fear and stress response of layers reared under two different spectrums of LED light. Tonic immobility Inversion Stress measures Treatment Latency to right (s) Flapping intensity (flaps/s) Corticosterone (pg/ml) Heterophil to lymphocyte Ratio Composite asymmetry score (mm) 18 wk of age Red 310.4 5.74 3122 0.40 1.52 White 278.6 5.46 2976 0.35 1.47 SEM 14.6 0.9 313 0.03 0.07 42 wk of age Red 276.3 4.91 6,112a 0.58a 1.15a White 274.1 4.61 10,715b 1.14b 1.59b SEM 13.1 0.16 1,219 0.07 0.06 72 wk of age Red 317.3 5.39 926a 0.80a 1.64a White 368.1 5.29 3,401b 1.50b 2.07b SEM 14.3 0.12 276 0.14 0.07 Overall Red 301.3 5.35 2,912a 0.59a 1.44a White 306.5 5.12 5,697b 0.99b 1.71b SEM 8.1 0.07 425 0.06 0.04 Age 18 wk 294.5a 5.60a 3,049a 0.37a 1.50a 42 wk 275.2a 4.76b 8,413b 0.86b 1.37a 72 wk 342.7b 5.34a 2,163a 1.16c 1.85b SEM 8.1 0.07 425 0.06 0.04 Treatment F1, 633 = 0.12, P = 0.73 F1, 633 = 2.28, P = 0.13 F1,194 = 9.71, P = 0.002 F1,210 = 15.55, P < 0.001 F1,633 = 12.93, P < 0.001 Period F2,633 = 6.14, P = 0.002 F2,633 = 11.51, P < 0.001 F2,194 = 24.93, P < 0.001 F2,210 = 19.68, P < 0.001 F2,633 = 14.17, P < 0.001 Interaction F2, 633 = 2.24, P = 0.11 F2,633 = 0.17, P = 0.84 F2,194 = 3.32, P = 0.04 F2,210 = 5.13, P = 0.007 F2,633 = 4.56, P = 0.01 Tonic immobility Inversion Stress measures Treatment Latency to right (s) Flapping intensity (flaps/s) Corticosterone (pg/ml) Heterophil to lymphocyte Ratio Composite asymmetry score (mm) 18 wk of age Red 310.4 5.74 3122 0.40 1.52 White 278.6 5.46 2976 0.35 1.47 SEM 14.6 0.9 313 0.03 0.07 42 wk of age Red 276.3 4.91 6,112a 0.58a 1.15a White 274.1 4.61 10,715b 1.14b 1.59b SEM 13.1 0.16 1,219 0.07 0.06 72 wk of age Red 317.3 5.39 926a 0.80a 1.64a White 368.1 5.29 3,401b 1.50b 2.07b SEM 14.3 0.12 276 0.14 0.07 Overall Red 301.3 5.35 2,912a 0.59a 1.44a White 306.5 5.12 5,697b 0.99b 1.71b SEM 8.1 0.07 425 0.06 0.04 Age 18 wk 294.5a 5.60a 3,049a 0.37a 1.50a 42 wk 275.2a 4.76b 8,413b 0.86b 1.37a 72 wk 342.7b 5.34a 2,163a 1.16c 1.85b SEM 8.1 0.07 425 0.06 0.04 Treatment F1, 633 = 0.12, P = 0.73 F1, 633 = 2.28, P = 0.13 F1,194 = 9.71, P = 0.002 F1,210 = 15.55, P < 0.001 F1,633 = 12.93, P < 0.001 Period F2,633 = 6.14, P = 0.002 F2,633 = 11.51, P < 0.001 F2,194 = 24.93, P < 0.001 F2,210 = 19.68, P < 0.001 F2,633 = 14.17, P < 0.001 Interaction F2, 633 = 2.24, P = 0.11 F2,633 = 0.17, P = 0.84 F2,194 = 3.32, P = 0.04 F2,210 = 5.13, P = 0.007 F2,633 = 4.56, P = 0.01 a,b,cSuperscripts within column and time point indicate significant differences P < 0.05. View Large Table 2. Fear and stress response of layers reared under two different spectrums of LED light. Tonic immobility Inversion Stress measures Treatment Latency to right (s) Flapping intensity (flaps/s) Corticosterone (pg/ml) Heterophil to lymphocyte Ratio Composite asymmetry score (mm) 18 wk of age Red 310.4 5.74 3122 0.40 1.52 White 278.6 5.46 2976 0.35 1.47 SEM 14.6 0.9 313 0.03 0.07 42 wk of age Red 276.3 4.91 6,112a 0.58a 1.15a White 274.1 4.61 10,715b 1.14b 1.59b SEM 13.1 0.16 1,219 0.07 0.06 72 wk of age Red 317.3 5.39 926a 0.80a 1.64a White 368.1 5.29 3,401b 1.50b 2.07b SEM 14.3 0.12 276 0.14 0.07 Overall Red 301.3 5.35 2,912a 0.59a 1.44a White 306.5 5.12 5,697b 0.99b 1.71b SEM 8.1 0.07 425 0.06 0.04 Age 18 wk 294.5a 5.60a 3,049a 0.37a 1.50a 42 wk 275.2a 4.76b 8,413b 0.86b 1.37a 72 wk 342.7b 5.34a 2,163a 1.16c 1.85b SEM 8.1 0.07 425 0.06 0.04 Treatment F1, 633 = 0.12, P = 0.73 F1, 633 = 2.28, P = 0.13 F1,194 = 9.71, P = 0.002 F1,210 = 15.55, P < 0.001 F1,633 = 12.93, P < 0.001 Period F2,633 = 6.14, P = 0.002 F2,633 = 11.51, P < 0.001 F2,194 = 24.93, P < 0.001 F2,210 = 19.68, P < 0.001 F2,633 = 14.17, P < 0.001 Interaction F2, 633 = 2.24, P = 0.11 F2,633 = 0.17, P = 0.84 F2,194 = 3.32, P = 0.04 F2,210 = 5.13, P = 0.007 F2,633 = 4.56, P = 0.01 Tonic immobility Inversion Stress measures Treatment Latency to right (s) Flapping intensity (flaps/s) Corticosterone (pg/ml) Heterophil to lymphocyte Ratio Composite asymmetry score (mm) 18 wk of age Red 310.4 5.74 3122 0.40 1.52 White 278.6 5.46 2976 0.35 1.47 SEM 14.6 0.9 313 0.03 0.07 42 wk of age Red 276.3 4.91 6,112a 0.58a 1.15a White 274.1 4.61 10,715b 1.14b 1.59b SEM 13.1 0.16 1,219 0.07 0.06 72 wk of age Red 317.3 5.39 926a 0.80a 1.64a White 368.1 5.29 3,401b 1.50b 2.07b SEM 14.3 0.12 276 0.14 0.07 Overall Red 301.3 5.35 2,912a 0.59a 1.44a White 306.5 5.12 5,697b 0.99b 1.71b SEM 8.1 0.07 425 0.06 0.04 Age 18 wk 294.5a 5.60a 3,049a 0.37a 1.50a 42 wk 275.2a 4.76b 8,413b 0.86b 1.37a 72 wk 342.7b 5.34a 2,163a 1.16c 1.85b SEM 8.1 0.07 425 0.06 0.04 Treatment F1, 633 = 0.12, P = 0.73 F1, 633 = 2.28, P = 0.13 F1,194 = 9.71, P = 0.002 F1,210 = 15.55, P < 0.001 F1,633 = 12.93, P < 0.001 Period F2,633 = 6.14, P = 0.002 F2,633 = 11.51, P < 0.001 F2,194 = 24.93, P < 0.001 F2,210 = 19.68, P < 0.001 F2,633 = 14.17, P < 0.001 Interaction F2, 633 = 2.24, P = 0.11 F2,633 = 0.17, P = 0.84 F2,194 = 3.32, P = 0.04 F2,210 = 5.13, P = 0.007 F2,633 = 4.56, P = 0.01 a,b,cSuperscripts within column and time point indicate significant differences P < 0.05. View Large All birds started the study with similar (P > 0.05) plasma corticosterone concentrations, heterophil to lymphocyte ratios, and composite asymmetry scores. However, there was an overall treatment difference (P > 0.05) with the RED treatment having lower plasma corticosterone concentrations (2,912 pg/ml), heterophil to lymphocyte ratios (0.59), and composite asymmetry scores (1.44) than the WHITE treatment (5,697 pg/ml, 0.99, and 1.71, respectively). There was also an interaction (P < 0.05) between lighting treatment and age in the all the stress measures. This is because at 42 wk of age sampling and again at the 72 wk of age sampling all stress measures were lower (P < 0.05) in the RED treatment compared to the WHITE treatment. Differences (P > 0.05) in within measures were also found between the different sampling ages. The 42 d sampling had the highest corticosterone concentrations likely because it was during the summer and heat stress possibly was occurring. DISCUSSION The results of this current study did not illustrate a difference in egg production or quality. This is not consistent with previous research that showed when birds were reared under red light they produced more eggs (Pyrzak et al., 1987; Huber-Eicher et al., 2013; Svobodova et al., 2015). However, the lights used in previous studies were monochromatic red light and were being compared to white light or other monochromatic colors. In this current study, the RED treatment light also contained white light (Figure 1); therefore, it is possible that even though there was more relatively red light in the RED treatment, the WHITE treatment had enough red light to stimulate similar production. Though it is worth noting while not statistically significant the RED treatment did lay on average 6.5 eggs more per bird during the 72 wk study. This amount of extra eggs would be financially significant on a large modern poultry farm. Although the fear response of birds in this current study did not differ, their stress responses did differ. All birds started the experiment with similar stress responses as measured by plasma corticosterone, heterophil to lymphocyte ratio, and composite asymmetry score. However, at the 42 wk of age sampling the RED treatment had lower stress responses in all three measures. This continued at the final sampling at 72 weeks of age. This is consistent with Archer and Byrd (unpublished data) which also observed layers in the early laying phase having lower stress responses when they were reared under similar red lights when compared to birds reared under white lights. Svobodova et al. (2015) also observed lower mortality in birds reared under red light that could be related to this lowered stress response, however, that requires more investigation to confirm. No difference in fear response was observed between treatments. It is possible that any benefits to reduced fear response under red light could have been lost due to how birds perceive light. Red light appears brighter to birds than to humans (Prayitno and Phillips, 1997). The intensity of light used in this current study was set using a light meter designed to measure intensity based on human vision. This could mean that the RED treatment likely perceived the light as brighter compared to the WHITE treatment. Although the retina can be stimulated with light at low intensities, the extra-retinal photoreceptors require higher light intensities (Harrison and Becker, 1969). Therefore, it is possible that the extra-retinal photoreceptors play a larger role in the stress response, though this requires further investigation. Although the RED treatment did not affect egg quality or egg production statistically significantly in this study, it did increase egg production numerically. This increase is consistent with previous research and demonstrates again that red light is an important factor for laying hen production. Furthermore, although the RED treatment did not lower fear responses, it lowered the stress response of the hens in that treatment. This lowered stress response may be related to the numerical increase in total eggs produced per hen though further investigation is needed. The improved stress response of the RED treatment illustrates improved welfare and that optimizing the light spectrum for the age and type of animal may be needed to optimize welfare during production. REFERENCES Archer G. S. , Mench J. A. . 2013 . The effects of light stimulation during incubation on indicators of stress susceptibility in broilers . Poult. Sci. 92 : 3103 – 3108 . Google Scholar Crossref Search ADS PubMed Archer G. S. , Mench J. A. . 2014 . 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The effect of parachlorophenylalanine and active immunization against vasoactive intestinal peptide on reproductive activities of broiler breeder hens photostimulated with green light . Biol. Reprod. 88 : 83 . Google Scholar Crossref Search ADS PubMed Newberry R. C. , Blair R. . 1993 . Behavioral-responses of broiler-chickens to handling-effects of dietary tryptophan and 2 lighting regimens . Poult. Sci . 72 : 1237 – 1244 . Google Scholar Crossref Search ADS PubMed Pang S. F. , Ralph C. L. , Reilly D. P. . 1974 . Melatonin in chicken brain—its origin, diurnal-variation, and regional distribution . Gen. Comp. Endocrinol . 22 : 499 – 506 . Google Scholar Crossref Search ADS PubMed Pelham R. W. , Ralph C. L. , Campbell I. M. . 1972 . Mass spectral identification of melatonin in blood . Biochem. Biophys. Res. Commun. 46 : 1236 – 1241 . Google Scholar Crossref Search ADS PubMed Perry G. C. 2004 . Lighting . Pages 299 – 312 in Welfare of the Laying Hen . Perry G. C. , ed. Vol. 27 . CABI , Cambridge, MA . Prayitno D. S. , Phillips C. J. C. . 1997 . Equating the perceived intensity of coloured lights to hens . Br. Poult. Sci. 38 : 136 – 141 . Google Scholar Crossref Search ADS PubMed Prescott N. B. , Wathes C. M. . 1999 . Spectral sensitivity of the domestic fowl (Gallus g. domesticus) . Br. Poult. Sci . 40 : 332 – 339 . Google Scholar Crossref Search ADS PubMed Pyrzak R. , Snapir N. , Goodman G. , Perek M. . 1987 . The effect of light wavelength on the production and quality of eggs of the domestic hen . Theriogenol. 28 : 947 – 960 . Google Scholar Crossref Search ADS Reddy I. J. , David C. G. , Selvaraju S. , Mondal S. , Kiran G. R. . 2012 . GnRH-1 mRNA, LH surges, steroid hormones, egg production, and intersequence pause days alter in birds exposed to longer wavelength of light in the later stages of production in Gallus gallus domesticus . Trop. Anim. Health Prod . 44 : 1311 – 1317 . Google Scholar Crossref Search ADS PubMed Rozenboim I. , Biran I. , Uni Z. , Robinzon B. , Halevy O. . 1999a . The effect of monochromatic light on broiler growth and development . Poult. Sci. 78 : 135 – 138 . Google Scholar Crossref Search ADS Rozenboim I. , Robinzon B. , Rosenstrauch A. . 1999b . Effect of light source and regimen on growing broilers . Br. Poult. Sci. 40 : 452 – 457 . Google Scholar Crossref Search ADS Siopes T. D. , Wilson W. O. . 1980 . Participation of the eyes in the photosexual response of Japanese Quail (Coturnix-Coturnix-Japonica) . Biol. Reprod. 23 : 352 – 357 . Google Scholar Crossref Search ADS PubMed Sultana S. , Hassan M. R. , Choe H. S. , Ryu K. S. . 2013 . The effect of monochromatic and mixed LED light colour on the behaviour and fear responses of broiler chicken . Avian Biol. Res. 6 : 207 – 214 . Google Scholar Crossref Search ADS Svobodova J. , Tümova E. , Popelarova E. , Chodova D. . 2015 . Effect of light colour on egg production and egg contamination . Czech J. Anim. Sci. 60 : 550 – 556 . Google Scholar Crossref Search ADS Yoshizawa T. 1992 . The road to color-vision—structure, evolution and function of chicken and gecko visual pigments . Photochem. Photobiol. 56 : 859 – 867 . Google Scholar Crossref Search ADS PubMed © 2018 Poultry Science Association Inc. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Poultry Science Oxford University Press

How does red light affect layer production, fear, and stress?

Poultry Science, Volume 98 (1) – Jan 1, 2019

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© 2018 Poultry Science Association Inc.
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0032-5791
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Abstract

ABSTRACT Light-emitting diode (LED) light bulbs are becoming more prevalent in layer production as unlike CFLs they are dimmable and are even more energy-efficient than CFLs. There is also discussion on whether the spectrum of light that is produced by the bulb can affect production, stress, and behavior of laying hens. To investigate if differences between how the bulb that produce different wavelengths of light affect these factors, we raised White Leghorn hens under either a bulb that produced white light with the addition of red light (Once, Inc, AgriShift MLL; RED) or a bulb that produced only white light (Overdrive, L10NA19DIM 3000 K; WHITE). Each treatment consisted of 36 White Leghorn hens, and the experiment was replicated three times for a total of 108 hens per treatment. Production parameters including % hens in lay, feed conversion, average egg weight, total eggs per hen, eggshell breaking strength, and Haugh units were measured. Hen fear response during tonic immobility and inversion was documented at 3 time points during the study (18, 42, and 72 wk of age). Stress susceptibility was also quantified using plasma corticosterone, heterophil to lymphocyte ratio, and composite asymmetry score at the same time points as the fear testing. No production parameters were affected by lighting type (P > 0.05). Lighting type did not affect tonic immobility or inversion response (P > 0.05). By 42 wk of age and continuing on until 72 wk of age, the RED treatment had lower plasma corticosterone concentrations, lower heterophil to lymphocyte ratios, and lower composite asymmetry scores than the WHITE treatment (P < 0.05). The results indicate that including red light in the spectrum of light layers are reared under can lower stress susceptibility but had no effect on fear response or production parameters when compared to white light. INTRODUCTION The wavelength of light has been shown to affect behavior, welfare, and performance of the poultry (Manser, 1996; Rozenboim et al., 1999a; 1999b). Birds unlike mammals have retinal photoreceptors responsible for vision and extra-retinal photoreceptors responsible for detecting photoperiod and synchronizing their physiology to the environment (Kumar and Rani, 1999). The location of these photoreceptors are found in three main organs: the eye, pineal gland, and hypothalamus. The retina contains three photoreceptors: rods, cones, and double cones (Perry, 2004). The cones are responsible for color vision and are tetrachromatic in birds (Prescott and Wathes, 1999). Photoreceptive pigments within these cones have a maximum sensitivity to violet (415 nm), blue (455 nm), green (508 nm), or red (571 nm) (Yoshizawa, 1992; Perry, 2004). The pineal gland, which is first sensitive to light at 3 d into embryogenesis (Cooper et al., 2011), controls the secretion of serotonin and melatonin. These hormones are involved in control of circadian rhythm, endocrine functions, mobility, body temperature, and reproduction in poultry (Pelham et al., 1972; Baxter et al., 2014). It has been demonstrated that if white light intensity is under 4 lux it cannot penetrate the skull and reach the pineal gland that results in the repression of the secretion of serotonin and melatonin (Lewis and Morris, 2006). Furthermore, different wavelengths of light directly penetrate the hypothalamus, which cause different effects (Lewis and Morris, 2006). Long wavelength light directly penetrates into the skull and brain, and then reaches the hypothalamus (Baxter et al., 2014). Lights utilizing short wavelengths must be at higher intensities order to affect the hypothalamus (Benoit, 1964; Baxter et al., 2014). Extra-retinal photoreceptors have been found to be sensitive to the red wavelengths of the electromagnetic spectrum (Cedden and Göğer, 1999). Birds perceive light differently due to differences in spectral sensitivity and density of photoreceptive pigments found in their retinas (Prescott and Wathes, 1999). The perceived intensity is relative to the spectral power output of the light and the spectral sensitivity of the bird retina. Red light appears brighter to birds than blue light at lower intensities (Prayitno and Phillips, 1997). Furthermore, the retina can be stimulated with light at low intensities, but the extra-retinal photoreceptors require higher light intensities (Harrison and Becker, 1969). This results in lower wavelengths such as blue or green light requiring higher intensities than longer wavelengths such as red light to stimulate hypothalamic photoreceptors (Pang et al., 1974). The retina of birds has a peak sensitivity to yellow and green wavelengths; however, birds exposed to green light have a delay in the rate of sexual maturity, lower egg production, and lower levels of steroids and GnRH-I mRNA expression (Siopes and Wilson, 1980; Mobarkey et al., 2010; Gongruttananun, 2011; Mobarkey et al., 2013; Baxter et al., 2014). Therefore, if only the retina is stimulated by the green light it will inhibit reproduction (Siopes and Wilson, 1980; Mobarkey et al., 2010; Gongruttananun, 2011; Mobarkey et al., 2013). Conversely, exposure to higher wavelengths has been demonstrated to increase egg production and resulted in higher steroid and gonadotropin concentrations and higher neuropeptide mRNA expression (Foss et al., 1972; Reddy et al., 2012; Hassan et al., 2013; Huber-Eicher et al., 2013; Baxter et al., 2014). Previous studies have shown that laying hens reared under monochromatic red light had higher egg production than those reared under white, green (Pyrzak et al., 1987; Huber-Eicher et al., 2013; Baxter et al., 2014; Svobodova et al.,2015), and blue light-emitting diode (LED) light (Hassan et al., 2013). Borille et al. (2013) found that birds reared under white light produced more eggs than those reared under red light. Li et al. (2014) found that birds reared under red and white light had the heaviest egg, whereas those reared under blue and green light had the lightest eggs. However, egg shell strength was higher in birds reared under green light than those reared under white and blue light (Li et al., 2014). Behavior and stress have also been demonstrated to be affected by light wavelength. Birds have been shown to spend more time sitting or standing under short wavelengths (blue/green) and exhibited more locomotion under longer (red/yellow) wavelengths (Sultana et al., 2013). Birds reared under red/yellow light exhibit tonic immobility for longer periods of time, indicating that they were more fearful than the short-wavelength exposed birds (Sultana et al., 2013). Green light has been demonstrated to reduce time spent feeding (Huber-Eicher et al., 2013). D’Eath and Stone (1999) found that birds reared under red light had lowered social recognition. Archer and Byrd (unpublished data) observed that birds reared with a high level red light had lower stress susceptibility, as indicated by corticosterone, composite asymmetry, and humoral immunity) than those reared under white light or light with a high level of blue light. Svobodova et al. (2015) observed that the lowest mortality rate was 12.65% for the laying hens reared under the red light, whereas the highest mortality was 14.30% for the hens raised under the blue light possibly indicating less stress susceptibility in birds reared under red light. The objective of this study was to determine how two different commercially available LED lights affected laying hen production, fear, and stress. The first light was a warm white LED fixture and the second was a white LED fixture that contained monochromatic red light. Hens were reared under the these lights for an entire lay cycle and it was hypothesized that the addition of red light would increase production and lower fear and stress responses. MATERIALS AND METHODS Animals and Husbandry A total of 216 White Leghorn hens were used in this experiment. Birds were housed starting at 17 wk of age and until the end of the study (72 wk of age) in a two-level A-frame cage system in groups of three hens per cage. Cages measured (520.7 mm deep × 412.8 mm wide × 393.7 mm high). The hens were housed in three rooms that were kept at a consistent temperature of 70°F, and the light schedule had 16 h of light to 8 h of darkness with an average illumination of 40 lux at the feeder height as measured with a light meter (MK350, UPRTek, Jhunan Taiwan). Half of the birds were housed under LED light bulbs which had white and red LEDs (Once, AgriShift® MLM-Red; Red), whereas the other half were housed under LED light bulbs that where only white (Overdrive, L10NA19DIM 3000 K; White). The spectrum of each light type is presented in Figure 1 as measured with a light meter (MK350, UPRTek, Jhunan Taiwan). Each of the three rooms was split down the middle with a light-proof barrier but allowed for the air space to be shared by both treatments. Each room contained both treatments with one on each side of the barrier with each room having 12 replicate cages per treatment. The birds were managed according to the guidelines set forth in the Guide for the Care and Use of Agricultural Animals in Research and Teaching (FASS, 2010) and all procedures were approved by the Texas A&M University animal care committee (IACUC #2015-0235). Figure 1. View largeDownload slide Spectrum of the lighting treatments used in this study. Figure 1. View largeDownload slide Spectrum of the lighting treatments used in this study. Production Measurements Bird performance was evaluated through daily measurements of egg production and egg weight. The former was used to calculate flock production by determining the percentage of the flock that was in lay from day to day; the latter allowed for the calculation of the flock's feed conversion rate. Measurements of feed consumption and feed conversion were calculated monthly based on the weight of the eggs produced and the weight of the feed given to the birds throughout each month. On a biweekly basis, eggs were collected from each cage and analyzed for egg quality measurements including: Haugh unit and shell breaking strength. Haugh units were determined using an automatic scale and albumen-height gage (2/A, Futura, Lohne Germany). Breaking strength was measured using the QC-SPA System (Technical Services and Supplies, York, England). Fear Measurements Tonic immobility and inversion tests to measure fear responses. Both fear tests were conducted at 18, 42, and 72 wk of age within treatment rooms. Tonic immobility testing was carried out as described by Archer and Mench (2014) on all birds. In brief, birds were placed on their backs in a cradle and held there for 15 s. If the bird righted before 10 s, tonic immobility was re-induced up to 3 times. If the bird could not be induced in 3 attempts, it was scored as 0. Latency to right and number of induction attempts was recorded. The test was terminated in 600 s if a bird failed to right and that bird was scored as 600. Longer latency to right indicates greater level of fear. All birds were also subjected to an inversion test, as described by Newberry and Blair (1993) and Archer and Mench (2014). Each bird was removed from its cage and then inverted it by holding it by its legs with one hand until the bird ceased to wing flap, or for 30 s. We determined the duration of and number of wing flaps (Cannon, ZR900, Melville, NY, USA; 24 frames/s). Intensity of flapping was then calculated with greater intensity indicates greater level of fear. Stress Measures At 18, 42, and 72 wk age blood samples were collected from 12 birds per treatment per room. Blood sampling occurred several days after fear testing and took less than 1 min. Between 1 and 2 mL of blood were collected using syringes from wing vein of each bird, and a drop was used to prepare a blood-smear slide. The remaining blood was injected into a plasma separation gel and lithium heparin vaccutainer (BD 368056, BD, Franklin Lakes, NJ), which was temporarily stored in an ice bath. Once all samples had been taken, the vaccutainers were spun down in a Beckman GS-6R centrifuge (Beckman Coulter, Brea, CA) for 15 min at 4,000 RPM to separate the cells from the plasma. The plasma was poured into 2 mL microcentrifuge tubes and stored at −19°C until further analysis. The blood-smear slides were stained using a hematology staining kit (Cat# 25034, Polysciences Inc, Warrington, PA). Plasma corticosterone concentrations were measured using a commercially available ELISA kit (Enzo Life Sciences, ADI-901-097, Farmingdale, NY). The inter and intra-assay %CV were both under 5%. Higher plasma corticosterone concentrations indicate greater stress susceptibility. The heterophil/lymphocyte ratio was measured by taking the blood smear slides prepared earlier and observing them under 1,000X magnification (10X eyepiece and 100X oil emersion lens) using an Omax DCE-2 microscope (Kent, WA). The numbers of both heterophils and lymphocytes observed were counted until the total observed number reached 100. A keystroke counter was used to accurately keep track of the number of cells observed. Greater ratios indicate greater stress susceptibility. Physical asymmetry of all birds was also measured at each time point, following the protocol outlined in Archer and Mench (2013). Using a calibrated Craftsman IP54 Digital Caliper (Sears Holdings, Hoffman Estates, IL), the middle toe length, metatarsal length, and metatarsal width were measured for both the right and left legs. All measurements were done by one individual. The composite asymmetry score was calculated by taking the sum of the absolute value of left minus right of each trait, and then dividing by the total number of traits. Thus, the formula for this trial would be (∣L−R∣MTL+∣L−R∣ML+∣L−R∣MW)/3 = composite asymmetry score. Greater composite asymmetry score indicates greater stress susceptibility. Statistical Analysis To investigate the data, the GLM procedure was used with treatment, testing period, and the interaction of the two as factors. Room/experimental replication was not found to be significant so data were combined. Pen nested within treatment was the error term used to test for treatment effects. The least significant difference test was used to test all planned comparisons. All of the assumptions were tested (Shapiro–Wilk test for normality, Levene's test for homogeneity of variance). No transformations were needed to meet assumptions. All analyses were performed using SAS 9.3 for Windows (SAS Institute Inc.). Significant differences were at P < 0.05. RESULTS Production The production data are presented in Table 1. Lighting treatment did not affect egg shell breaking strength, Haugh units, % of hens in lay, feed conversion, average egg weight, or total eggs produced per bird (P > 0.05). There was also no interaction between lighting treatment and lay period in any of the production parameters measured (P > 0.05). All production parameters measured differed from the 18 to 42 wk period when compared to the 42 to 72 wk period (P < 0.05). Table 1. Egg quality and production of layers reared under two different spectrums of LED light. Treatment Breaking strength (g) Haugh units % Hens in lay Feed conversion (g of feed per g of egg) Average egg weight (g) Total eggs/bird 18 to 42 wk of age Red 3200.2 105.9 93.4 1.92 56.8 137.2 White 3255.8 105.6 91.4 1.91 56.6 134.4 SEM 21.0 0.1 0.7 0.03 0.2 1.4 42 to 72 wk of age Red 3427.0 90.7 81.9 1.72 62.0 177.8 White 3515.0 89.9 80.3 1.71 61.9 174.2 SEM 29.7 0.3 0.9 0.02 0.2 2.5 Overall Red 3320.5 98.2 86.5 1.80 59.7 315.0 White 3389.9 97.7 84.8 1.79 59.5 308.5 SEM 22.5 0.2 0.8 0.02 0.2 3.7 Period 18 to 42 wk 3228a 105.8a 91.4a 1.92a 56.7a 134.4a 42 to 72 wk 3471b 90.3b 80.3b 1.71b 62.0b 174.2b SEM 20.8 0.7 0.8 0.03 0.3 6.2 Treatment F1,143 = 3.75, P = 0.06 F1,143 = 1.93, P = 0.17 F1,143 = 2.19, P = 0.14 F1,23 = 0.00, P = 0.98 F1,143 = 0.27, P = 0.61 F1,23 = 0.30, P = 0.59 Period F1,143 = 46.05, P < 0.001 F1,143 = 1670.35, P < 0.001 F1,143 = 84.98, P < 0.001 F1,23 = 32.91, P = 0.001 F1,143 = 320.89, P < 0.001 F1,23 = 377.86, P < 0.001 Interaction F1,143 = 0.26, P = 0.61 F1,143 = 0.60, P = 0.44 F1,143 = 0.01, P = 0.91 F1,23 = 0.01, P = 0.93 F1,143 = 0.04, P = 0.84 F1,23 = 0.13, P = 0.73 Treatment Breaking strength (g) Haugh units % Hens in lay Feed conversion (g of feed per g of egg) Average egg weight (g) Total eggs/bird 18 to 42 wk of age Red 3200.2 105.9 93.4 1.92 56.8 137.2 White 3255.8 105.6 91.4 1.91 56.6 134.4 SEM 21.0 0.1 0.7 0.03 0.2 1.4 42 to 72 wk of age Red 3427.0 90.7 81.9 1.72 62.0 177.8 White 3515.0 89.9 80.3 1.71 61.9 174.2 SEM 29.7 0.3 0.9 0.02 0.2 2.5 Overall Red 3320.5 98.2 86.5 1.80 59.7 315.0 White 3389.9 97.7 84.8 1.79 59.5 308.5 SEM 22.5 0.2 0.8 0.02 0.2 3.7 Period 18 to 42 wk 3228a 105.8a 91.4a 1.92a 56.7a 134.4a 42 to 72 wk 3471b 90.3b 80.3b 1.71b 62.0b 174.2b SEM 20.8 0.7 0.8 0.03 0.3 6.2 Treatment F1,143 = 3.75, P = 0.06 F1,143 = 1.93, P = 0.17 F1,143 = 2.19, P = 0.14 F1,23 = 0.00, P = 0.98 F1,143 = 0.27, P = 0.61 F1,23 = 0.30, P = 0.59 Period F1,143 = 46.05, P < 0.001 F1,143 = 1670.35, P < 0.001 F1,143 = 84.98, P < 0.001 F1,23 = 32.91, P = 0.001 F1,143 = 320.89, P < 0.001 F1,23 = 377.86, P < 0.001 Interaction F1,143 = 0.26, P = 0.61 F1,143 = 0.60, P = 0.44 F1,143 = 0.01, P = 0.91 F1,23 = 0.01, P = 0.93 F1,143 = 0.04, P = 0.84 F1,23 = 0.13, P = 0.73 a,bSuperscripts within column and time point indicate significant differences P < 0.05. View Large Table 1. Egg quality and production of layers reared under two different spectrums of LED light. Treatment Breaking strength (g) Haugh units % Hens in lay Feed conversion (g of feed per g of egg) Average egg weight (g) Total eggs/bird 18 to 42 wk of age Red 3200.2 105.9 93.4 1.92 56.8 137.2 White 3255.8 105.6 91.4 1.91 56.6 134.4 SEM 21.0 0.1 0.7 0.03 0.2 1.4 42 to 72 wk of age Red 3427.0 90.7 81.9 1.72 62.0 177.8 White 3515.0 89.9 80.3 1.71 61.9 174.2 SEM 29.7 0.3 0.9 0.02 0.2 2.5 Overall Red 3320.5 98.2 86.5 1.80 59.7 315.0 White 3389.9 97.7 84.8 1.79 59.5 308.5 SEM 22.5 0.2 0.8 0.02 0.2 3.7 Period 18 to 42 wk 3228a 105.8a 91.4a 1.92a 56.7a 134.4a 42 to 72 wk 3471b 90.3b 80.3b 1.71b 62.0b 174.2b SEM 20.8 0.7 0.8 0.03 0.3 6.2 Treatment F1,143 = 3.75, P = 0.06 F1,143 = 1.93, P = 0.17 F1,143 = 2.19, P = 0.14 F1,23 = 0.00, P = 0.98 F1,143 = 0.27, P = 0.61 F1,23 = 0.30, P = 0.59 Period F1,143 = 46.05, P < 0.001 F1,143 = 1670.35, P < 0.001 F1,143 = 84.98, P < 0.001 F1,23 = 32.91, P = 0.001 F1,143 = 320.89, P < 0.001 F1,23 = 377.86, P < 0.001 Interaction F1,143 = 0.26, P = 0.61 F1,143 = 0.60, P = 0.44 F1,143 = 0.01, P = 0.91 F1,23 = 0.01, P = 0.93 F1,143 = 0.04, P = 0.84 F1,23 = 0.13, P = 0.73 Treatment Breaking strength (g) Haugh units % Hens in lay Feed conversion (g of feed per g of egg) Average egg weight (g) Total eggs/bird 18 to 42 wk of age Red 3200.2 105.9 93.4 1.92 56.8 137.2 White 3255.8 105.6 91.4 1.91 56.6 134.4 SEM 21.0 0.1 0.7 0.03 0.2 1.4 42 to 72 wk of age Red 3427.0 90.7 81.9 1.72 62.0 177.8 White 3515.0 89.9 80.3 1.71 61.9 174.2 SEM 29.7 0.3 0.9 0.02 0.2 2.5 Overall Red 3320.5 98.2 86.5 1.80 59.7 315.0 White 3389.9 97.7 84.8 1.79 59.5 308.5 SEM 22.5 0.2 0.8 0.02 0.2 3.7 Period 18 to 42 wk 3228a 105.8a 91.4a 1.92a 56.7a 134.4a 42 to 72 wk 3471b 90.3b 80.3b 1.71b 62.0b 174.2b SEM 20.8 0.7 0.8 0.03 0.3 6.2 Treatment F1,143 = 3.75, P = 0.06 F1,143 = 1.93, P = 0.17 F1,143 = 2.19, P = 0.14 F1,23 = 0.00, P = 0.98 F1,143 = 0.27, P = 0.61 F1,23 = 0.30, P = 0.59 Period F1,143 = 46.05, P < 0.001 F1,143 = 1670.35, P < 0.001 F1,143 = 84.98, P < 0.001 F1,23 = 32.91, P = 0.001 F1,143 = 320.89, P < 0.001 F1,23 = 377.86, P < 0.001 Interaction F1,143 = 0.26, P = 0.61 F1,143 = 0.60, P = 0.44 F1,143 = 0.01, P = 0.91 F1,23 = 0.01, P = 0.93 F1,143 = 0.04, P = 0.84 F1,23 = 0.13, P = 0.73 a,bSuperscripts within column and time point indicate significant differences P < 0.05. View Large Fear and Stress Fear and stress response data are presented in Table 2. There was no effect of lighting treatment (P > 0.05) or interaction of lighting treatment and age (P > 0.05) on latency to right during TI testing or in flapping intensity during inversion testing. Differences in latency to right and flapping intensity were observed between the different testing ages (P > 0.05). The layers overall had shorter latency to right (275.2 s) and less intense flapping (4.76 flaps/s) at 42 wk of age when compared to 18 (294.5 s and 5.60 flaps/s) and 72 (342.7 s and 5.34 flaps/s) weeks of age. Table 2. Fear and stress response of layers reared under two different spectrums of LED light. Tonic immobility Inversion Stress measures Treatment Latency to right (s) Flapping intensity (flaps/s) Corticosterone (pg/ml) Heterophil to lymphocyte Ratio Composite asymmetry score (mm) 18 wk of age Red 310.4 5.74 3122 0.40 1.52 White 278.6 5.46 2976 0.35 1.47 SEM 14.6 0.9 313 0.03 0.07 42 wk of age Red 276.3 4.91 6,112a 0.58a 1.15a White 274.1 4.61 10,715b 1.14b 1.59b SEM 13.1 0.16 1,219 0.07 0.06 72 wk of age Red 317.3 5.39 926a 0.80a 1.64a White 368.1 5.29 3,401b 1.50b 2.07b SEM 14.3 0.12 276 0.14 0.07 Overall Red 301.3 5.35 2,912a 0.59a 1.44a White 306.5 5.12 5,697b 0.99b 1.71b SEM 8.1 0.07 425 0.06 0.04 Age 18 wk 294.5a 5.60a 3,049a 0.37a 1.50a 42 wk 275.2a 4.76b 8,413b 0.86b 1.37a 72 wk 342.7b 5.34a 2,163a 1.16c 1.85b SEM 8.1 0.07 425 0.06 0.04 Treatment F1, 633 = 0.12, P = 0.73 F1, 633 = 2.28, P = 0.13 F1,194 = 9.71, P = 0.002 F1,210 = 15.55, P < 0.001 F1,633 = 12.93, P < 0.001 Period F2,633 = 6.14, P = 0.002 F2,633 = 11.51, P < 0.001 F2,194 = 24.93, P < 0.001 F2,210 = 19.68, P < 0.001 F2,633 = 14.17, P < 0.001 Interaction F2, 633 = 2.24, P = 0.11 F2,633 = 0.17, P = 0.84 F2,194 = 3.32, P = 0.04 F2,210 = 5.13, P = 0.007 F2,633 = 4.56, P = 0.01 Tonic immobility Inversion Stress measures Treatment Latency to right (s) Flapping intensity (flaps/s) Corticosterone (pg/ml) Heterophil to lymphocyte Ratio Composite asymmetry score (mm) 18 wk of age Red 310.4 5.74 3122 0.40 1.52 White 278.6 5.46 2976 0.35 1.47 SEM 14.6 0.9 313 0.03 0.07 42 wk of age Red 276.3 4.91 6,112a 0.58a 1.15a White 274.1 4.61 10,715b 1.14b 1.59b SEM 13.1 0.16 1,219 0.07 0.06 72 wk of age Red 317.3 5.39 926a 0.80a 1.64a White 368.1 5.29 3,401b 1.50b 2.07b SEM 14.3 0.12 276 0.14 0.07 Overall Red 301.3 5.35 2,912a 0.59a 1.44a White 306.5 5.12 5,697b 0.99b 1.71b SEM 8.1 0.07 425 0.06 0.04 Age 18 wk 294.5a 5.60a 3,049a 0.37a 1.50a 42 wk 275.2a 4.76b 8,413b 0.86b 1.37a 72 wk 342.7b 5.34a 2,163a 1.16c 1.85b SEM 8.1 0.07 425 0.06 0.04 Treatment F1, 633 = 0.12, P = 0.73 F1, 633 = 2.28, P = 0.13 F1,194 = 9.71, P = 0.002 F1,210 = 15.55, P < 0.001 F1,633 = 12.93, P < 0.001 Period F2,633 = 6.14, P = 0.002 F2,633 = 11.51, P < 0.001 F2,194 = 24.93, P < 0.001 F2,210 = 19.68, P < 0.001 F2,633 = 14.17, P < 0.001 Interaction F2, 633 = 2.24, P = 0.11 F2,633 = 0.17, P = 0.84 F2,194 = 3.32, P = 0.04 F2,210 = 5.13, P = 0.007 F2,633 = 4.56, P = 0.01 a,b,cSuperscripts within column and time point indicate significant differences P < 0.05. View Large Table 2. Fear and stress response of layers reared under two different spectrums of LED light. Tonic immobility Inversion Stress measures Treatment Latency to right (s) Flapping intensity (flaps/s) Corticosterone (pg/ml) Heterophil to lymphocyte Ratio Composite asymmetry score (mm) 18 wk of age Red 310.4 5.74 3122 0.40 1.52 White 278.6 5.46 2976 0.35 1.47 SEM 14.6 0.9 313 0.03 0.07 42 wk of age Red 276.3 4.91 6,112a 0.58a 1.15a White 274.1 4.61 10,715b 1.14b 1.59b SEM 13.1 0.16 1,219 0.07 0.06 72 wk of age Red 317.3 5.39 926a 0.80a 1.64a White 368.1 5.29 3,401b 1.50b 2.07b SEM 14.3 0.12 276 0.14 0.07 Overall Red 301.3 5.35 2,912a 0.59a 1.44a White 306.5 5.12 5,697b 0.99b 1.71b SEM 8.1 0.07 425 0.06 0.04 Age 18 wk 294.5a 5.60a 3,049a 0.37a 1.50a 42 wk 275.2a 4.76b 8,413b 0.86b 1.37a 72 wk 342.7b 5.34a 2,163a 1.16c 1.85b SEM 8.1 0.07 425 0.06 0.04 Treatment F1, 633 = 0.12, P = 0.73 F1, 633 = 2.28, P = 0.13 F1,194 = 9.71, P = 0.002 F1,210 = 15.55, P < 0.001 F1,633 = 12.93, P < 0.001 Period F2,633 = 6.14, P = 0.002 F2,633 = 11.51, P < 0.001 F2,194 = 24.93, P < 0.001 F2,210 = 19.68, P < 0.001 F2,633 = 14.17, P < 0.001 Interaction F2, 633 = 2.24, P = 0.11 F2,633 = 0.17, P = 0.84 F2,194 = 3.32, P = 0.04 F2,210 = 5.13, P = 0.007 F2,633 = 4.56, P = 0.01 Tonic immobility Inversion Stress measures Treatment Latency to right (s) Flapping intensity (flaps/s) Corticosterone (pg/ml) Heterophil to lymphocyte Ratio Composite asymmetry score (mm) 18 wk of age Red 310.4 5.74 3122 0.40 1.52 White 278.6 5.46 2976 0.35 1.47 SEM 14.6 0.9 313 0.03 0.07 42 wk of age Red 276.3 4.91 6,112a 0.58a 1.15a White 274.1 4.61 10,715b 1.14b 1.59b SEM 13.1 0.16 1,219 0.07 0.06 72 wk of age Red 317.3 5.39 926a 0.80a 1.64a White 368.1 5.29 3,401b 1.50b 2.07b SEM 14.3 0.12 276 0.14 0.07 Overall Red 301.3 5.35 2,912a 0.59a 1.44a White 306.5 5.12 5,697b 0.99b 1.71b SEM 8.1 0.07 425 0.06 0.04 Age 18 wk 294.5a 5.60a 3,049a 0.37a 1.50a 42 wk 275.2a 4.76b 8,413b 0.86b 1.37a 72 wk 342.7b 5.34a 2,163a 1.16c 1.85b SEM 8.1 0.07 425 0.06 0.04 Treatment F1, 633 = 0.12, P = 0.73 F1, 633 = 2.28, P = 0.13 F1,194 = 9.71, P = 0.002 F1,210 = 15.55, P < 0.001 F1,633 = 12.93, P < 0.001 Period F2,633 = 6.14, P = 0.002 F2,633 = 11.51, P < 0.001 F2,194 = 24.93, P < 0.001 F2,210 = 19.68, P < 0.001 F2,633 = 14.17, P < 0.001 Interaction F2, 633 = 2.24, P = 0.11 F2,633 = 0.17, P = 0.84 F2,194 = 3.32, P = 0.04 F2,210 = 5.13, P = 0.007 F2,633 = 4.56, P = 0.01 a,b,cSuperscripts within column and time point indicate significant differences P < 0.05. View Large All birds started the study with similar (P > 0.05) plasma corticosterone concentrations, heterophil to lymphocyte ratios, and composite asymmetry scores. However, there was an overall treatment difference (P > 0.05) with the RED treatment having lower plasma corticosterone concentrations (2,912 pg/ml), heterophil to lymphocyte ratios (0.59), and composite asymmetry scores (1.44) than the WHITE treatment (5,697 pg/ml, 0.99, and 1.71, respectively). There was also an interaction (P < 0.05) between lighting treatment and age in the all the stress measures. This is because at 42 wk of age sampling and again at the 72 wk of age sampling all stress measures were lower (P < 0.05) in the RED treatment compared to the WHITE treatment. Differences (P > 0.05) in within measures were also found between the different sampling ages. The 42 d sampling had the highest corticosterone concentrations likely because it was during the summer and heat stress possibly was occurring. DISCUSSION The results of this current study did not illustrate a difference in egg production or quality. This is not consistent with previous research that showed when birds were reared under red light they produced more eggs (Pyrzak et al., 1987; Huber-Eicher et al., 2013; Svobodova et al., 2015). However, the lights used in previous studies were monochromatic red light and were being compared to white light or other monochromatic colors. In this current study, the RED treatment light also contained white light (Figure 1); therefore, it is possible that even though there was more relatively red light in the RED treatment, the WHITE treatment had enough red light to stimulate similar production. Though it is worth noting while not statistically significant the RED treatment did lay on average 6.5 eggs more per bird during the 72 wk study. This amount of extra eggs would be financially significant on a large modern poultry farm. Although the fear response of birds in this current study did not differ, their stress responses did differ. All birds started the experiment with similar stress responses as measured by plasma corticosterone, heterophil to lymphocyte ratio, and composite asymmetry score. However, at the 42 wk of age sampling the RED treatment had lower stress responses in all three measures. This continued at the final sampling at 72 weeks of age. This is consistent with Archer and Byrd (unpublished data) which also observed layers in the early laying phase having lower stress responses when they were reared under similar red lights when compared to birds reared under white lights. Svobodova et al. (2015) also observed lower mortality in birds reared under red light that could be related to this lowered stress response, however, that requires more investigation to confirm. No difference in fear response was observed between treatments. It is possible that any benefits to reduced fear response under red light could have been lost due to how birds perceive light. Red light appears brighter to birds than to humans (Prayitno and Phillips, 1997). The intensity of light used in this current study was set using a light meter designed to measure intensity based on human vision. This could mean that the RED treatment likely perceived the light as brighter compared to the WHITE treatment. Although the retina can be stimulated with light at low intensities, the extra-retinal photoreceptors require higher light intensities (Harrison and Becker, 1969). Therefore, it is possible that the extra-retinal photoreceptors play a larger role in the stress response, though this requires further investigation. Although the RED treatment did not affect egg quality or egg production statistically significantly in this study, it did increase egg production numerically. 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Journal

Poultry ScienceOxford University Press

Published: Jan 1, 2019

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