TY - JOUR
AU - van Laar, H.
AB - ABSTRACT An experiment was conducted to determine the effects of diet composition, feeding level (FL), and BW on endogenous phosphorous losses (EPL) using growing-finishing (GF) pigs and sows. After an adaptation period, 48 GF pigs (initial BW 90.5 kg) and 48 just-weaned sows (initial BW 195 kg), both individually housed, were allotted to 12 dietary treatments in a 2 × 3 × 2 factorial arrangement. Treatments were animal type (GF pigs or sows), diet composition (a semipurified starch (STA), inulin (INU), or lignocellulose (CEL) based low-P diet), and FL (2.0 or 3.0 kg/d). Digestibility of DM, OM, CP, crude fat, and carbohydrates (COH), and fecal P excretion (in g/d, mg/kg DMI, and g/(kg BW·d)) were determined using TiO2 as indigestible marker. Digestibility of OM and COH differed among diets (P < 0.001) and was greatest in both types of pigs fed the STA diet and lowest in those fed the CEL diet. While digestibility of OM and COH was similar in sows and GF pigs that were fed the STA diet and the CEL diet, on the INU diet, sows had, compared with GF pigs, a greater digestibility of OM (92.2 vs. 87.2%) and COH (92.5 vs. 88.4%), respectively. Both BW and FL increased fecal P excretion (g/d). When expressed in mg/kg DMI, P excretion was higher in sows than in GF pigs on the STA diet (498 versus 236 mg/kg DMI), the INU diet (526 vs. 316 mg/kg DMI), and the CEL diet (928 vs. 342 mg/kg DMI). When expressed in mg/(kg BW·d), however, P excretion was similar in GF pigs and sows that were fed the STA diet and in those that were fed the INU diet, whereas it was greater in sows than in GF pigs that were fed the CEL diet (11.6 vs. 7.3 mg/(kg BW·d)). The results of this study indicate that EPL (mg/kg DMI) in pigs substantially increase with increasing BW. Application of EPL (mg/kg DMI) determined in GF pigs may underestimate EPL and therefore P requirements in gestating sows. Moreover, EPL is diet dependent and increases with an increasing content of dietary nonstarch polysaccharides (NSP). The degree of this increase may differ between sows and GF pigs and seems to depend on properties of dietary fiber. INTRODUCTION Recommendations for the supply of dietary phosphorous (P) to pigs are generally based on factorial models of P requirements (Jongbloed et al., 2003; GfE, 2008; NRC, 2012). Phosphorous requirements of growing-finishing (GF) pigs and sows are determined by requirements for maintenance, i.e., to replace minimum urinary losses and basal endogenous P losses (EPL) from the gut, P retention in the body, P excretion in milk, and the postabsorptive utilization of dietary P. In earlier models, fecal P losses were considered proportional to BW (Jongbloed et al., 2003; GfE, 2008). More recently, NRC (2012) related basal EPL to feed intake with a value of 190 mg/kg DMI in GF pigs and sows. However, in most studies the effects of BW and DMI were correlated. Therefore, the first aim of this study was to separate the influence of BW and DMI on EPL. Little attention has been paid to diet-specific EPL. Similar to the definition of endogenous AA losses (Stein et al., 2007), basal EPL represent the minimum quantity of P inevitably lost by the pig due to the physical flow of DM through the digestive tract and the metabolic state of the animal and are not influenced by diet composition. Diet-specific EPL may be due to fiber content and composition, as demonstrated for endogenous AA losses with increasing content of dietary nonstarch polysaccharides (NSP), thus reducing protein digestibility (Le Goff and Noblet, 2001; Van der Peet-Schwering et al., 2002; Libao-Mercado et al., 2006). Moreover, an increasing difference in nutrient digestibility between sows and GF pigs with increasing dietary NSP content was observed (Le Goff and Noblet, 2001). We hypothesized that EPL determined in GF pigs underestimate those in sows and that high contents of NSP may increase EPL, with differential effects between sows and GF pigs. Thus, this experiment was conducted to determine the separate effects of BW and DMI and the effects of fermentable and nonfermentable NSP on EPL in GF pigs and gestating sows. MATERIAL AND METHODS The experiment with GF pigs and gestating sows was conducted at the Swine Research Centre of Trouw Nutrition (Sint Anthonis, the Netherlands) from March until July, 2014. All procedures were in agreement with the Dutch law on animal experiments and approved by the Animal Ethics Committee of Utrecht University, the Netherlands. A selection of results of this study has been published in Bikker et al. (2016) to determine basal EPL in sows and GF pigs fed starch based diets. Animals, Housing, and Design In this study with a randomized block design, 2 groups of 24 female GF pigs (Hypor Maxter x Hypor, initial BW 90.5 ± 0.95 kg) and 2 groups of 24 primi- and multiparous just-weaned sows (Hypor Libria, initial BW 195 ± 5.2 kg) were allotted to 12 treatments in a 2 × 3 × 2 factorial arrangement. Blocks were based on BW and parity for GF pigs and sows, respectively, to assure their equal distribution among treatments. Treatments were animal type (GF pigs or sows), diet composition (a semipurified starch (STA), inulin (INU), or lignocellulose (CEL) based low-P diet), and feeding level (FL; 2 or 3 kg/d). From weaning to mating, sows received the STA, INU, or CEL diet, while supplemented with an adequate concentration of P from monocalcium phosphate and Ca from limestone to adapt to the composition of the diets. Subsequently, the low-P diets were supplied during 22 d from mating onward. The GF pigs were fed the adequate-P diets during a 14-d adaptation period and received the low-P diets during a 22-d period thereafter. The sows were individually housed in pens of 2.35 × 0.6 m with a partly slatted concrete floor. The GF pigs were individually housed in pens of 2.05 × 1.0 m with partly slatted concrete floor. Environmental conditions, temperature, and ventilation rate were automatically controlled and appropriate for the stage of the pigs. Diets and Feeding The STA, INU, and CEL diets with adequate and low P content (Table 1) mainly differed in starch, fermentable NSP, and nonfermentable NSP content. The STA low-P diet was based on ingredients with the lowest achievable P content, mainly corn starch and sucrose, and with spray-dried porcine plasma powder (Proglobulin 80 P; Sonac, Bad Bremstadt, Germany) and gelatin (Pro-Bind Plus; Sonac, Vuren, the Netherlands) as protein sources. In addition, microbial phytase (500 FTU, Natuphos 10000G, BASF) was included to facilitate digestion and absorption of any residual phytate-P by the pigs to minimize P of dietary origin in the feces (Kerr et al., 2010; Rutherfurd et al., 2014). In the INU low-P diet 200 g/kg demineralized inulin (Prebiofeed 95; Cosucra Groupe Warcoing S.A., Division Socodé, Warcoing, Belgium) was included as source of rapidly fermentable NSP at the expense of 200 g/kg cornstarch. In the CEL low-P diet 200 g/kg lignocellulose (Fibercell; Agromed, Kremsmünster, Austria) was included as source of nonfermentable NSP at the expense of 200 g/kg cornstarch. Titanium dioxide (0.25%) was included in the low-P diet as an indigestible marker. In the adaptation period, monocalcium phosphate and limestone were included in all diets at the expense of cornstarch. All pigs had free access to water from a nipple drinker and feed was manually provided in 2 equal portions per day (700 and 1500 h) as ground diet (3-mm screen) in a dry feeder. Feed refusals were removed and weighed daily before the morning feeding. Table 1. Composition of experimental starch (STA), inuline (INU), and lignocellulose (CEL) based diets (g/kg; as-is basis) Ingredient  STA  INU  CEL  Adequate P  Low P  Adequate P  Low P  Adequate P  Low P  Corn starch1  586.4  611.7  386.4  411.7  386.4  411.7  Sucrose  150.0  150.0  150.0  150.0  150.0  150.0  Inulin1  –  –  200.0  200.0  –  –  Lignocellulose1  50.0  50.0  50.0  50.0  250.0  250.0  Soybean oil  28.6  20.0  28.6  20.0  28.6  20.0  Spray dried plasma1  90.3  90.3  90.3  90.3  90.3  90.3  Gelatin1  50.0  50.0  50.0  50.0  50.0  50.0  L-lysine-HCl  0.4  0.4  0.4  0.4  0.4  0.4  DL-methionine  1.8  1.8  1.8  1.8  1.8  1.8  L-threonine  1.0  1.0  1.0  1.0  1.0  1.0  L-tryptophan  0.5  0.5  0.5  0.5  0.5  0.5  L-isoleucine  1.7  1.7  1.7  1.7  1.7  1.7  Limestone  13.6  8.0  13.6  8.0  13.6  8.0  Monocalcium phosphate  12.6  0  12.6  0  12.6  0  Potassium carbonate  5.0  5.0  5.0  5.0  5.0  5.0  Magnesium oxide  2.0  2.0  2.0  2.0  2.0  2.0  Premix vit. and min.2  5.0  5.0  5.0  5.0  5.0  5.0  Phytase3  0.1  0.1  0.1  0.1  0.1  0.1  Titanium oxide  –  2.5  –  2.5  –  2.5  Chromium oxide mix  1.0  –  1.0  –  1.0  –  Analyzed nutrient content  DM  907  905  915  917  912  912  CP  124.4  125.0  123.1  123.1  125.0  125.0  Crude fiber  35.4  33.8  36.1  33.6  167.0  159.4  Starch  487  509  344  360  333  355  Crude ash  38.1  26.4  37.9  26.7  39.1  27.0  Phosphorous  3.47  0.38  3.77  0.32  3.55  0.42  Calcium  7.32  3.21  7.37  3.08  7.42  3.24  NE, MJ/kg4  10.9  10.9  10.9  10.9  10.9  10.9  AID lysine4  7.30  7.30  7.30  7.3  7.3  7.3  Ingredient  STA  INU  CEL  Adequate P  Low P  Adequate P  Low P  Adequate P  Low P  Corn starch1  586.4  611.7  386.4  411.7  386.4  411.7  Sucrose  150.0  150.0  150.0  150.0  150.0  150.0  Inulin1  –  –  200.0  200.0  –  –  Lignocellulose1  50.0  50.0  50.0  50.0  250.0  250.0  Soybean oil  28.6  20.0  28.6  20.0  28.6  20.0  Spray dried plasma1  90.3  90.3  90.3  90.3  90.3  90.3  Gelatin1  50.0  50.0  50.0  50.0  50.0  50.0  L-lysine-HCl  0.4  0.4  0.4  0.4  0.4  0.4  DL-methionine  1.8  1.8  1.8  1.8  1.8  1.8  L-threonine  1.0  1.0  1.0  1.0  1.0  1.0  L-tryptophan  0.5  0.5  0.5  0.5  0.5  0.5  L-isoleucine  1.7  1.7  1.7  1.7  1.7  1.7  Limestone  13.6  8.0  13.6  8.0  13.6  8.0  Monocalcium phosphate  12.6  0  12.6  0  12.6  0  Potassium carbonate  5.0  5.0  5.0  5.0  5.0  5.0  Magnesium oxide  2.0  2.0  2.0  2.0  2.0  2.0  Premix vit. and min.2  5.0  5.0  5.0  5.0  5.0  5.0  Phytase3  0.1  0.1  0.1  0.1  0.1  0.1  Titanium oxide  –  2.5  –  2.5  –  2.5  Chromium oxide mix  1.0  –  1.0  –  1.0  –  Analyzed nutrient content  DM  907  905  915  917  912  912  CP  124.4  125.0  123.1  123.1  125.0  125.0  Crude fiber  35.4  33.8  36.1  33.6  167.0  159.4  Starch  487  509  344  360  333  355  Crude ash  38.1  26.4  37.9  26.7  39.1  27.0  Phosphorous  3.47  0.38  3.77  0.32  3.55  0.42  Calcium  7.32  3.21  7.37  3.08  7.42  3.24  NE, MJ/kg4  10.9  10.9  10.9  10.9  10.9  10.9  AID lysine4  7.30  7.30  7.30  7.3  7.3  7.3  1Analyzed P content (g/kg) in corn starch 0.24, inulin (Prebiofeed 95; Speerstra Feed Ingredients, Lemmer, The Netherlands) 0.10, lignocellulose (Fibercell; Agromed, Kremünster, Austria) 0.14, spray-dried plasma (Proglobulin 80P; Sonac, Bad Bramstedt, Germany) 1.03, Gelatin (Pro-Bind Plus; Sonac, Vuren, the Netherlands) 0.97. 2Provided per kg of diet: vitamin A, 10,000 IU; vitamin D3, 2,000 IU; vitamin E, 40 IU; vitamin K3, 2.0 mg; thiamine, 0.75 mg; riboflavin, 5.0 mg; D-pantothenic acid, 15 mg; niacin, 60 mg; vitamin B12, 20 mg; folic acid, 2.5 mg; pyridoxine, 1.0 mg; choline chloride 400 mg; biotin, 300 mg, Fe (FeSO4–H2O), 15 mg Cu (CuSO4–5H2O); 80 mg; Zn (ZnSO4–H2O) 60 mg; Mn (MnO), 40 mg; I (KI), 1.0 mg; Se (Na2SeO3–5H2O), 0.3 mg. 3Provided per kg of diet 500 FTU phytase (Natuphos 5000 G; BASF, Ludwigshafen am Rhein, Germany). 4NE and apparent ileal digestible (AID) lysine based on CVB 2011 Feed Table. Chemical composition and nutritional value of feedstuffs. View Large Table 1. Composition of experimental starch (STA), inuline (INU), and lignocellulose (CEL) based diets (g/kg; as-is basis) Ingredient  STA  INU  CEL  Adequate P  Low P  Adequate P  Low P  Adequate P  Low P  Corn starch1  586.4  611.7  386.4  411.7  386.4  411.7  Sucrose  150.0  150.0  150.0  150.0  150.0  150.0  Inulin1  –  –  200.0  200.0  –  –  Lignocellulose1  50.0  50.0  50.0  50.0  250.0  250.0  Soybean oil  28.6  20.0  28.6  20.0  28.6  20.0  Spray dried plasma1  90.3  90.3  90.3  90.3  90.3  90.3  Gelatin1  50.0  50.0  50.0  50.0  50.0  50.0  L-lysine-HCl  0.4  0.4  0.4  0.4  0.4  0.4  DL-methionine  1.8  1.8  1.8  1.8  1.8  1.8  L-threonine  1.0  1.0  1.0  1.0  1.0  1.0  L-tryptophan  0.5  0.5  0.5  0.5  0.5  0.5  L-isoleucine  1.7  1.7  1.7  1.7  1.7  1.7  Limestone  13.6  8.0  13.6  8.0  13.6  8.0  Monocalcium phosphate  12.6  0  12.6  0  12.6  0  Potassium carbonate  5.0  5.0  5.0  5.0  5.0  5.0  Magnesium oxide  2.0  2.0  2.0  2.0  2.0  2.0  Premix vit. and min.2  5.0  5.0  5.0  5.0  5.0  5.0  Phytase3  0.1  0.1  0.1  0.1  0.1  0.1  Titanium oxide  –  2.5  –  2.5  –  2.5  Chromium oxide mix  1.0  –  1.0  –  1.0  –  Analyzed nutrient content  DM  907  905  915  917  912  912  CP  124.4  125.0  123.1  123.1  125.0  125.0  Crude fiber  35.4  33.8  36.1  33.6  167.0  159.4  Starch  487  509  344  360  333  355  Crude ash  38.1  26.4  37.9  26.7  39.1  27.0  Phosphorous  3.47  0.38  3.77  0.32  3.55  0.42  Calcium  7.32  3.21  7.37  3.08  7.42  3.24  NE, MJ/kg4  10.9  10.9  10.9  10.9  10.9  10.9  AID lysine4  7.30  7.30  7.30  7.3  7.3  7.3  Ingredient  STA  INU  CEL  Adequate P  Low P  Adequate P  Low P  Adequate P  Low P  Corn starch1  586.4  611.7  386.4  411.7  386.4  411.7  Sucrose  150.0  150.0  150.0  150.0  150.0  150.0  Inulin1  –  –  200.0  200.0  –  –  Lignocellulose1  50.0  50.0  50.0  50.0  250.0  250.0  Soybean oil  28.6  20.0  28.6  20.0  28.6  20.0  Spray dried plasma1  90.3  90.3  90.3  90.3  90.3  90.3  Gelatin1  50.0  50.0  50.0  50.0  50.0  50.0  L-lysine-HCl  0.4  0.4  0.4  0.4  0.4  0.4  DL-methionine  1.8  1.8  1.8  1.8  1.8  1.8  L-threonine  1.0  1.0  1.0  1.0  1.0  1.0  L-tryptophan  0.5  0.5  0.5  0.5  0.5  0.5  L-isoleucine  1.7  1.7  1.7  1.7  1.7  1.7  Limestone  13.6  8.0  13.6  8.0  13.6  8.0  Monocalcium phosphate  12.6  0  12.6  0  12.6  0  Potassium carbonate  5.0  5.0  5.0  5.0  5.0  5.0  Magnesium oxide  2.0  2.0  2.0  2.0  2.0  2.0  Premix vit. and min.2  5.0  5.0  5.0  5.0  5.0  5.0  Phytase3  0.1  0.1  0.1  0.1  0.1  0.1  Titanium oxide  –  2.5  –  2.5  –  2.5  Chromium oxide mix  1.0  –  1.0  –  1.0  –  Analyzed nutrient content  DM  907  905  915  917  912  912  CP  124.4  125.0  123.1  123.1  125.0  125.0  Crude fiber  35.4  33.8  36.1  33.6  167.0  159.4  Starch  487  509  344  360  333  355  Crude ash  38.1  26.4  37.9  26.7  39.1  27.0  Phosphorous  3.47  0.38  3.77  0.32  3.55  0.42  Calcium  7.32  3.21  7.37  3.08  7.42  3.24  NE, MJ/kg4  10.9  10.9  10.9  10.9  10.9  10.9  AID lysine4  7.30  7.30  7.30  7.3  7.3  7.3  1Analyzed P content (g/kg) in corn starch 0.24, inulin (Prebiofeed 95; Speerstra Feed Ingredients, Lemmer, The Netherlands) 0.10, lignocellulose (Fibercell; Agromed, Kremünster, Austria) 0.14, spray-dried plasma (Proglobulin 80P; Sonac, Bad Bramstedt, Germany) 1.03, Gelatin (Pro-Bind Plus; Sonac, Vuren, the Netherlands) 0.97. 2Provided per kg of diet: vitamin A, 10,000 IU; vitamin D3, 2,000 IU; vitamin E, 40 IU; vitamin K3, 2.0 mg; thiamine, 0.75 mg; riboflavin, 5.0 mg; D-pantothenic acid, 15 mg; niacin, 60 mg; vitamin B12, 20 mg; folic acid, 2.5 mg; pyridoxine, 1.0 mg; choline chloride 400 mg; biotin, 300 mg, Fe (FeSO4–H2O), 15 mg Cu (CuSO4–5H2O); 80 mg; Zn (ZnSO4–H2O) 60 mg; Mn (MnO), 40 mg; I (KI), 1.0 mg; Se (Na2SeO3–5H2O), 0.3 mg. 3Provided per kg of diet 500 FTU phytase (Natuphos 5000 G; BASF, Ludwigshafen am Rhein, Germany). 4NE and apparent ileal digestible (AID) lysine based on CVB 2011 Feed Table. Chemical composition and nutritional value of feedstuffs. View Large Observations and Chemical Analysis Body weight of the pigs was determined at the start of the adaptation period and at the beginning and end of the experimental period. Body weight of the sows at the start of the experimental period was interpolated from the other 2 time points to avoid weighing of the sows at the time of mating and a possible influence on the breeding of the animals. Refused feed was collected and feed intake was calculated on a daily basis. Feed samples were based on a small aliquot of feed collected from each bag used during the trial period. Grab samples of feces were collected during 3 consecutive days at the times of feeding on d 20 to 22 in both GF pigs and sows by grab sampling from spontaneous defecation or via rectal stimulation. The 3-d fecal samples were pooled per animal, homogenized, freeze dried, and ground to pass a 1-mm mesh sieve using a Retsch ZM 100 mill (Retsch GmbH, Haan, Germany). In each of the 2 groups, samples of 2 out of the 4 pigs per treatment combination were analyzed for N and fat content. Ground feed and fecal samples were analyzed for DM by drying at 103°C (ISO 6496), ash by combustion to a constant weight at 550°C (ISO, 5984), N by using the Kjeldahl method (Kjeltec 8400/8460 analyzer and sampler unit (Foss, Hillerød, Denmark; ISO 5983), and crude fat after hydrolysis (ISO 6492). Phosphorus was determined spectrophotometrically (Evolution 201; Thermo scientific, Waltham, MA; ISO 6491), and Ca was determined with atomic absorption spectrometry (AA240 FS; Varian, Palo Alto, CA; ISO 6869). Titanium was determined by spectrophotometer (Evolution 201; Thermo scientific, Waltham, MA) after hydrolysis with H2SO4 (Tecator digestion system; FOSS, Hillerød, Denmark) and subsequent addition of peroxide (Myers et al., 2004). Starch in feed samples was determined using a spectrophotometer (Evolution 201; Thermo scientific, Waltham, MA) after enzymatic conversion into glucose (ISO 15914). The total carbohydrate fraction (CHO) in diets and feces was defined as OM minus CP and crude fat, and thus comprised the sum of starch, sugars, and NSP. Nutrient digestibility was determined using the marker method (Petersen and Stein, 2006). Daily excretion of P was determined assuming complete excretion of titanium ingested in the daily ration (Stein et al., 2007). Statistical Analyses The experimental data were analyzed by ANOVA as a randomized complete block design with group and block as random factors, pig as experimental unit, and animal type (GF pig and sow), dietary composition, FL, and their interactions as fixed factors using GenStat statistical software (GenStat 16th edition). Differences were considered significant at P ≤ 0.05. Fisher protected least significant difference was used to identify pairwise differences (P < 0.05) between dietary treatments within animal type and between GF pigs and sows within dietary treatment. RESULTS The sows on either FL and the GF pigs on the low FL readily consumed their daily ration. The GF pigs fed 3.0 kg/d had feed residuals and realized a mean intake of 2.62, 2.86, and 2.92 kg/d on the STA, INU, and CEL diets, respectively. Excretion of P per kg DMI was based on the actual feed intake. One GF pig transiently suffered from lameness and received a 3-d medical treatment. The other pigs remained healthy throughout the experiment. The pigs supplied the INU based diets were subjectively judged by the farm staff to have more loose feces, especially in the GF period. This was not related to the DM content of the feces, which was lower for the CEL diet compared to the other 2 diets (Table 2). Table 2. Dry matter content of feces (n = 4 per treatment) and apparent total tract digestibility (%; n = 4 per treatment) of OM, CP, crude fat, and carbohydrates (COH)1 in growing-finishing (GF) pigs and gestating sows, determined 20 to 22 d after change-over to a starch (STA), inuline (INU), or lignocellulose (CEL) based low-P diet supplied at a feeding level (FL) of either 2.0 or 3.0 kg/d   FL 2.0 kg/d  FL 3.0 kg/d    P-value2  STA  INU  CEL  STA  INU  CEL  SEM  Animal  FL  Diet  AxFL  AxD  FLxD  DM, g/kg                            GF pigs  373cd  374cd  320ab  353bc  340bc  301a  14.8  0.069  0.004  < 0.001  0.648  0.033  0.430  Sows  459e  411d  338abc  413d  405d  336abc  OM                            GF pigs  93.0def  87.8c  71.9a  93.0def  86.6b  72.1a  0.43  0.050  0.270  < 0.001  0.555  < 0.001  0.220  Sows  93.3ef  92.3de  72.2a  93.2f  92.1d  72.2a  CP                            GF pigs  94.9g  86.8b  91.7cde  95.4g  83.6a  91.4cd  0.39  0.003  0.007  < 0.001  0.217  < 0.001  < 0.001  Sows  95.3g  92.2def  92.6ef  95.1g  90.9c  92.9f  Crude fat                            GF pigs  88.1d  80.2abcd  77.1a  85.9bcd  79.9abc  76.3a  2.28  0.703  0.485  < 0.001  0.447  0.006  0.701  Sows  88.2d  78.2ab  80.9abcd  87.6cd  78.2ab  81.7abcd  COH1                            GF pigs  92.8d  89.1c  68.4a  93.1d  87.7b  68.3a  0.41  0.061  0.093  < 0.001  0.967  < 0.001  0.356  Sows  93.0d  92.6d  68.7a  92.7d  92.5d  68.2a    FL 2.0 kg/d  FL 3.0 kg/d    P-value2  STA  INU  CEL  STA  INU  CEL  SEM  Animal  FL  Diet  AxFL  AxD  FLxD  DM, g/kg                            GF pigs  373cd  374cd  320ab  353bc  340bc  301a  14.8  0.069  0.004  < 0.001  0.648  0.033  0.430  Sows  459e  411d  338abc  413d  405d  336abc  OM                            GF pigs  93.0def  87.8c  71.9a  93.0def  86.6b  72.1a  0.43  0.050  0.270  < 0.001  0.555  < 0.001  0.220  Sows  93.3ef  92.3de  72.2a  93.2f  92.1d  72.2a  CP                            GF pigs  94.9g  86.8b  91.7cde  95.4g  83.6a  91.4cd  0.39  0.003  0.007  < 0.001  0.217  < 0.001  < 0.001  Sows  95.3g  92.2def  92.6ef  95.1g  90.9c  92.9f  Crude fat                            GF pigs  88.1d  80.2abcd  77.1a  85.9bcd  79.9abc  76.3a  2.28  0.703  0.485  < 0.001  0.447  0.006  0.701  Sows  88.2d  78.2ab  80.9abcd  87.6cd  78.2ab  81.7abcd  COH1                            GF pigs  92.8d  89.1c  68.4a  93.1d  87.7b  68.3a  0.41  0.061  0.093  < 0.001  0.967  < 0.001  0.356  Sows  93.0d  92.6d  68.7a  92.7d  92.5d  68.2a  a–hMeans within a trait without common superscript are significantly different (P < 0.05). 1Carbohydrates (COH) in feed and feces calculated as OM- CP- crude fat. 2The model included fixed effects of animal type (A, sows, and GF pigs), feeding level (FL), diet (D), and their interactions. View Large Table 2. Dry matter content of feces (n = 4 per treatment) and apparent total tract digestibility (%; n = 4 per treatment) of OM, CP, crude fat, and carbohydrates (COH)1 in growing-finishing (GF) pigs and gestating sows, determined 20 to 22 d after change-over to a starch (STA), inuline (INU), or lignocellulose (CEL) based low-P diet supplied at a feeding level (FL) of either 2.0 or 3.0 kg/d   FL 2.0 kg/d  FL 3.0 kg/d    P-value2  STA  INU  CEL  STA  INU  CEL  SEM  Animal  FL  Diet  AxFL  AxD  FLxD  DM, g/kg                            GF pigs  373cd  374cd  320ab  353bc  340bc  301a  14.8  0.069  0.004  < 0.001  0.648  0.033  0.430  Sows  459e  411d  338abc  413d  405d  336abc  OM                            GF pigs  93.0def  87.8c  71.9a  93.0def  86.6b  72.1a  0.43  0.050  0.270  < 0.001  0.555  < 0.001  0.220  Sows  93.3ef  92.3de  72.2a  93.2f  92.1d  72.2a  CP                            GF pigs  94.9g  86.8b  91.7cde  95.4g  83.6a  91.4cd  0.39  0.003  0.007  < 0.001  0.217  < 0.001  < 0.001  Sows  95.3g  92.2def  92.6ef  95.1g  90.9c  92.9f  Crude fat                            GF pigs  88.1d  80.2abcd  77.1a  85.9bcd  79.9abc  76.3a  2.28  0.703  0.485  < 0.001  0.447  0.006  0.701  Sows  88.2d  78.2ab  80.9abcd  87.6cd  78.2ab  81.7abcd  COH1                            GF pigs  92.8d  89.1c  68.4a  93.1d  87.7b  68.3a  0.41  0.061  0.093  < 0.001  0.967  < 0.001  0.356  Sows  93.0d  92.6d  68.7a  92.7d  92.5d  68.2a    FL 2.0 kg/d  FL 3.0 kg/d    P-value2  STA  INU  CEL  STA  INU  CEL  SEM  Animal  FL  Diet  AxFL  AxD  FLxD  DM, g/kg                            GF pigs  373cd  374cd  320ab  353bc  340bc  301a  14.8  0.069  0.004  < 0.001  0.648  0.033  0.430  Sows  459e  411d  338abc  413d  405d  336abc  OM                            GF pigs  93.0def  87.8c  71.9a  93.0def  86.6b  72.1a  0.43  0.050  0.270  < 0.001  0.555  < 0.001  0.220  Sows  93.3ef  92.3de  72.2a  93.2f  92.1d  72.2a  CP                            GF pigs  94.9g  86.8b  91.7cde  95.4g  83.6a  91.4cd  0.39  0.003  0.007  < 0.001  0.217  < 0.001  < 0.001  Sows  95.3g  92.2def  92.6ef  95.1g  90.9c  92.9f  Crude fat                            GF pigs  88.1d  80.2abcd  77.1a  85.9bcd  79.9abc  76.3a  2.28  0.703  0.485  < 0.001  0.447  0.006  0.701  Sows  88.2d  78.2ab  80.9abcd  87.6cd  78.2ab  81.7abcd  COH1                            GF pigs  92.8d  89.1c  68.4a  93.1d  87.7b  68.3a  0.41  0.061  0.093  < 0.001  0.967  < 0.001  0.356  Sows  93.0d  92.6d  68.7a  92.7d  92.5d  68.2a  a–hMeans within a trait without common superscript are significantly different (P < 0.05). 1Carbohydrates (COH) in feed and feces calculated as OM- CP- crude fat. 2The model included fixed effects of animal type (A, sows, and GF pigs), feeding level (FL), diet (D), and their interactions. View Large Digestibility of OM, CP, COH (P < 0.001), and crude fat (P = 0.006) was affected by an interaction between animal type and diet (Table 2). The digestibility of OM, CP, and COH was greater (P < 0.05) in sows than in GF pigs fed the INU diet, but not for the pigs fed the other 2 diets. The digestibility of OM and COH was lower for the CEL diet than for the STA diet in both types of pigs, whereas digestibility of the INU was lower than the STA diet in GF pigs only. The CP digestibility in both sows and GF pigs was higher for the STA diet than for the other 2 diets, whereas CP digestibility of the other 2 diets only differed in GF pigs. The increase in FL reduced the digestibility of CP in the INU diet (P < 0.05) but not in the other 2 diets (interaction FL × D, P < 0.001). In Table 3, fecal P excretion is presented in g/d, mg/kg DMI, and mg/(kg BW·d). The fecal P excretion (g/d) was affected by animal type (P = 0.009), FL (P < 0.001), diet (P < 0.001), and their interactions. For all diets, the P excretion (g/d and mg/kg DMI) was greater in sows than in GF pigs, whereas for P excretion in mg/kg BW this difference between sows and GF pigs was only observed for the CEL diet. An increase in FL increased the P excretion in g/d in both sows and GF pigs, whereas it caused an overall decrease in P excretion expressed in mg/kg DMI. The P excretion (in g/d, mg/kg DMI, and mg/(kg BW·d)) was more than 50% greater in sows and GF pigs fed the CEL diet compared to the STA diet. In GF pigs, the P excretion (g/d, and mg/(kg BW·d)) fed the INU diet was not different from the CEL diet, whereas in sows the P excretion fed the INU diet was not different from the STA diet. Table 3. Fecal phosphorus (P) excretion in growing-finishing (GF) pigs (mean BW 107.5 kg) and gestating sows (mean BW 191 kg; n = 8 per treatment), determined 20 to 22 d after change-over to a starch (STA), inuline (INU), or lignocellulose (CEL) based low-P diet supplied at a feeding level (FL) of either 2.0 or 3.0 kg/d   FL 2.0 kg/d  FL 3.0 kg/d    P-value1  STA  INU  CEL  STA  INU  CEL  SEM  Animal  FL  Diet  AxFL  AxD  FLxD  P, g/d                            GF pigs  0.44a  0.58bc  0.68c  0.54ab  0.83d  0.83d  0.07  0.009  < 0.001  < 0.001  < 0.001  < 0.001  0.004  Sows  0.96d  1.02d  1.76f  1.26e  1.36e  2.44g  P, mg/kg DMI                            GF pigs  242a  317b  374c  230a  316b  311b  30.1  0.009  < 0.001  < 0.001  0.056  < 0.001  0.408  Sows  533ef  559f  964h  464cd  494de  892g  P, mg/(kg BW·d)  GF pigs  4.2a  5.4abc  6.9c  5.0ab  7.2c  7.7c  0.55  0.128  < 0.001  < 0.001  0.124  < 0.001  0.020  Sows  5.3abc  5.5abc  10.2d  5.9abc  6.9bc  13.0e    FL 2.0 kg/d  FL 3.0 kg/d    P-value1  STA  INU  CEL  STA  INU  CEL  SEM  Animal  FL  Diet  AxFL  AxD  FLxD  P, g/d                            GF pigs  0.44a  0.58bc  0.68c  0.54ab  0.83d  0.83d  0.07  0.009  < 0.001  < 0.001  < 0.001  < 0.001  0.004  Sows  0.96d  1.02d  1.76f  1.26e  1.36e  2.44g  P, mg/kg DMI                            GF pigs  242a  317b  374c  230a  316b  311b  30.1  0.009  < 0.001  < 0.001  0.056  < 0.001  0.408  Sows  533ef  559f  964h  464cd  494de  892g  P, mg/(kg BW·d)  GF pigs  4.2a  5.4abc  6.9c  5.0ab  7.2c  7.7c  0.55  0.128  < 0.001  < 0.001  0.124  < 0.001  0.020  Sows  5.3abc  5.5abc  10.2d  5.9abc  6.9bc  13.0e  a–hMeans within a trait without common superscript are significantly different (P < 0.05). 1The model included fixed effects of animal type (A, sows, and GF pigs), feeding level (FL), diet (D), and their interactions. View Large Table 3. Fecal phosphorus (P) excretion in growing-finishing (GF) pigs (mean BW 107.5 kg) and gestating sows (mean BW 191 kg; n = 8 per treatment), determined 20 to 22 d after change-over to a starch (STA), inuline (INU), or lignocellulose (CEL) based low-P diet supplied at a feeding level (FL) of either 2.0 or 3.0 kg/d   FL 2.0 kg/d  FL 3.0 kg/d    P-value1  STA  INU  CEL  STA  INU  CEL  SEM  Animal  FL  Diet  AxFL  AxD  FLxD  P, g/d                            GF pigs  0.44a  0.58bc  0.68c  0.54ab  0.83d  0.83d  0.07  0.009  < 0.001  < 0.001  < 0.001  < 0.001  0.004  Sows  0.96d  1.02d  1.76f  1.26e  1.36e  2.44g  P, mg/kg DMI                            GF pigs  242a  317b  374c  230a  316b  311b  30.1  0.009  < 0.001  < 0.001  0.056  < 0.001  0.408  Sows  533ef  559f  964h  464cd  494de  892g  P, mg/(kg BW·d)  GF pigs  4.2a  5.4abc  6.9c  5.0ab  7.2c  7.7c  0.55  0.128  < 0.001  < 0.001  0.124  < 0.001  0.020  Sows  5.3abc  5.5abc  10.2d  5.9abc  6.9bc  13.0e    FL 2.0 kg/d  FL 3.0 kg/d    P-value1  STA  INU  CEL  STA  INU  CEL  SEM  Animal  FL  Diet  AxFL  AxD  FLxD  P, g/d                            GF pigs  0.44a  0.58bc  0.68c  0.54ab  0.83d  0.83d  0.07  0.009  < 0.001  < 0.001  < 0.001  < 0.001  0.004  Sows  0.96d  1.02d  1.76f  1.26e  1.36e  2.44g  P, mg/kg DMI                            GF pigs  242a  317b  374c  230a  316b  311b  30.1  0.009  < 0.001  < 0.001  0.056  < 0.001  0.408  Sows  533ef  559f  964h  464cd  494de  892g  P, mg/(kg BW·d)  GF pigs  4.2a  5.4abc  6.9c  5.0ab  7.2c  7.7c  0.55  0.128  < 0.001  < 0.001  0.124  < 0.001  0.020  Sows  5.3abc  5.5abc  10.2d  5.9abc  6.9bc  13.0e  a–hMeans within a trait without common superscript are significantly different (P < 0.05). 1The model included fixed effects of animal type (A, sows, and GF pigs), feeding level (FL), diet (D), and their interactions. View Large DISCUSSION The analyzed P content in the low-P STA, INU, and CEL diet of 0.38, 0.32, and 0.42 g/kg, respectively, reflected the expected contents of 0.3 g/kg, based on the analyzed P content of the ingredients and confirmed adequate diet manufacturing. Although the diets were not completely free of P, we assume that the contribution of dietary P to fecal P excretion was negligible. We used ingredients with a high digestibility (Jongbloed and Kemme, 1990; Almeida and Stein, 2011; Alves et al., 2016), and phytase was included to enhance digestibility of a potentially minor amount of phytate-P in corn starch (Kerr et al., 2010; Rutherfurd et al., 2014). Digestibility of Nutrients The higher digestibility of OM, CP, crude fat, and COH in the STA diet compared to the INU and CEL diets was expected because total tract digestibility of nutrients in both sows and GF pigs generally decrease with increasing NSP content in the diet (Le Goff and Noblet, 2001; Rijnen et al. 2001; Rijnen, 2003). This is explained by the lack of digestive enzymes to degrade dietary NSP and the increase in endogenous losses with increasing NSP content (Libao-Mercado et al., 2006). Digestibility of nutrients is greater in highly fermentable NSP sources like INU (Souza da Silva et al., 2013) than in nonfermentable NSP sources like CEL (Baumgärtel et al., 2008; CVB, 2016). This explains the lower digestibility of OM and COH in the CEL diet compared to the INU diet. The CP digestibility, however, was lower in the INU diet than in the CEL diet. This effect of INU inclusion on CP digestibility was also reported for GF pigs by Lynch et al. (2007) and may be explained by increased excretion of bacterial protein synthesized during fermentation of NSP in the digestive tract (Le Goff and Noblet, 2001) using N from dietary origin or urea-N from the systemic circulation. In addition, effects of NSP sources on CP digestibility mediated by an effect on passage rate as reported by Hooda et al. (2011) cannot be excluded. The digestibility of nutrients was similar in GF pigs and sows fed the STA diet and in GF pigs and sows fed the CEL diet, whereas it was greater in sows than in GF pigs fed the INU diet. This is in line with results of Noblet and Le Goff (2001) reporting that the biggest difference in nutrient digestibility between sows and GF pigs is observed for ingredients rich in potentially fermentable NSP. The STA diet contained 61% corn starch and the digestibility of nutrients in corn starch is similar in sows and GF pigs (Noblet and Le Goff, 2001). The CEL diet contained 25% lignocellulose, which is resistant to degradation in the gastrointestinal tract in both sows and GF pigs (Noblet and Le Goff, 2001). Inulin in the INU diet is highly fermentable. The greater digestion of INU in sows than in GF pigs indicates a greater capacity for fermentation in sows, possibly related to a larger hindgut volume, a lower passage rate in the hindgut, and differences in hindgut microbiota (Noblet and Le Goff, 2001). The increase in FL decreased the COH digestibility in GF pigs (from 89.1 to 87.7%) but not in sows, suggesting that their digestive capacity may have limited maximum digestion of the INU diet in GF pigs. Fecal P Excretion In many studies, digestibility and excretion of P have been determined after an adaptation period of 4 to 5 d (Fan et al., 2001; Petersen and Stein, 2006). Nonetheless, Jongbloed (1987) argued that a 14-d period is required to allow adaptation to a diet limited in P content as used in P digestibility studies. Furthermore, Van der Peet-Schwering et al. (2002) concluded that sows completely adapt to an NSP-rich diet in a 2-wk period. Thus, we used a minimum 14-d period to adapt to the low-P diet in the present study. We have previously concluded that a minimum period of 14 d is necessary to obtain a stable basal fecal endogenous P excretion in pigs fed the STA diet with low-P content. The P excretion decreased from d 7 to d 14 after onset of feeding the low P diet, with no significant decrease thereafter (Bikker et al., 2016). The fecal P excretion in GF pigs fed the STA diet of 236 mg/kg DMI is in agreement with the studies of Almeida and Stein (2010) and Son and Kim (2015), who reported values for EPL of 199 and 214 mg/kg DMI, respectively. Fecal P excretion of a starch-based diet is often referred to as basal EPL and is used to calculate standardized P digestibility of feed ingredients (Petersen and Stein, 2006; Almeida and Stein, 2010). Petersen and Stein (2006) suggested that a high content of dietary fiber may increase total fecal EPL because of an increase in diet-dependent EPL. Indeed, inclusion of INU and CEL in the diets increased the fecal mg P excretion/kg DMI in GF pigs. In pigs, dietary fiber is the main substrate for microbiota in the gastrointestinal tract. Inclusion of dietary fiber has been shown to promote bacterial growth, resulting in a greater fecal excretion of amino acids, lipids, and minerals, including P, of bacterial origin (Mosenthin et al., 1994; Metzler and Mosenthin, 2008). Both soluble (e.g., inulin) and insoluble fiber (e.g., lignocellulose) sources may increase intestinal epithelial cell proliferation rate and the sloughing off of epithelial cells (Metzler and Mosenthin, 2008). This likely explains the increase in fecal P excretion in GF pigs that were fed the INU and CEL diets. Son and Kim (2015), however, did not find an effect of the inclusion of cellulose in P-free diets on fecal P excretion. These authors used a microcrystalline cellulose product, which was partly depolymerized cellulose from purified wood pulp, and suggested that this perhaps had a minimal physical influence on sloughing off of epithelial cells. Moreover, they included 4%, 8%, or 12% of cellulose at the expense of corn starch, whereas we replaced corn starch with 20% inulin or lignocellulose. The difference in inclusion level of cellulose may have contributed to the different effects on fecal P excretion between these 2 studies. Son and Kim (2015), however, suggested that the physical or chemical properties of dietary fiber are probably a more critical factor for EPL than the concentration of the dietary fiber. The results of our study indicate that dietary NSP increase fecal EPL above the level of basal EPL determined using low-fiber, starch-based diets. This implies that the P digestibility of feed ingredients as determined by replacing (corn) starch, using the regression method (Fan et al., 2001) or the substitution method (Fang et al., 2007) includes an unspecified fraction of diet-specific EPL and reflects the standardized rather than true P digestibility. The mean P excretion in sows fed the STA diet was 498 mg/kg DMI, approximately 2 times greater than in GF pigs on the STA diet at the same FL. Presumably, the difference between GF pigs and sows is largely explained by the effect of BW because the difference is much smaller and not significant when P excretion is expressed in mg/kg BW. In this study, the effects of BW and FL were separated, and the results illustrate that both have an independent effect on EPL. In Bikker et al. (2016) these effects were quantified by multiple linear regression. Our results imply that the adoption of an estimate of P excretion (mg/kg DMI) in GF pigs results in an underestimation of EPL for gestating sows. We cannot exclude that differences in physiological state between growing pigs and reproductive sows also influence fecal P excretion and influenced the EPL as determined in this study. However, we assume that differences in the postabsorptive P metabolism related to the reproductive state of the sows would more likely result in an effect on P excretion in the urine rather than P excretion via the feces. In both sows and GF pigs, the CEL diet increased the fecal P excretion compared to the STA diet, but the magnitude of increase was much bigger in sows. The inclusion of 20% lignocellulose at the expense of starch increased the EPL by 430 and 107 mg/kg DMI in sows and GF pigs, respectively. The reason of this large difference is not quite clear. It seems not related to differences in digestion and fermentation because of the similar digestibility of the CEL diet in GF pigs and sows (Table 2). We speculate that the passage of the bulk of indigestible lignocellulose with high water binding capacity may induce sloughing off of cells in proportion to the size of the bigger digestive tract in sows compared to GF pigs. In addition, contrary to the GF pigs, the INU diet did not increase the P excretion in sows on both the low and high FL. The small difference in digestibility of OM and COH between the STA and the INU diet in sows (1.0% and 0.3% unit difference, respectively) compared to GF pigs (5.8% and 4.5% difference, respectively) and a potentially slower passage rate in the hindgut of sows might be the reason that we did not find an increase in fecal P excretion in sows fed the INU diet. These differential effects of especially nonfermentable NSP between sows and GF pigs have important consequences because it may imply that diet-specific EPL of NSP-rich feed ingredients are greater in gestating sows than in growing pigs. Thus, the standardized P digestibility of these ingredients, as commonly determined in GF pigs (e.g., NRC, 2012; CVB, 2016), may overestimate the standardized P digestibility for gestating sows. Conclusion The results of this study indicate that EPL in pigs independently respond to increasing BW and DMI, and that EPL in gestating sows exceed these of GF pigs. Application of basal EPL (mg/kg DMI) determined in GF pigs may underestimate EPL in gestating sows. Endogenous P losses are diet dependent and will increase with increasing content of dietary NSP. The degree of this increase may differ between sows and GF pigs and may depend on the properties, e.g., fermentability of dietary fiber. LITERATURE CITED Almeida F. N. Stein H. H. 2010. 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TI - Endogenous phosphorus losses in growing-finishing pigs and gestating sows
JO - Journal of Animal Science
DO - 10.2527/jas.2016.1041
DA - 2017-04-01
UR - https://www.deepdyve.com/lp/oxford-university-press/endogenous-phosphorus-losses-in-growing-finishing-pigs-and-gestating-VLSn90rRJc
SP - 1637
EP - 1643
VL - 95
IS - 4
DP - DeepDyve
ER -