多重线性回归法测定猪内源磷排泄量及饲料磷真消化率的研究

本研究采用多重线性回归法测定生长猪内源磷排泄量及花生粕和豆粕磷的真消化率。选用6头健康大白×长白阉公猪为试验动物,平均体重为(24.8±1.42)kg。采用6×6拉丁方设计,设6个磷水平(0.09%、0.17%、0.26%、0.35%、0.43%、0.53%),以豆粕、葡萄糖、玉米淀粉等为基础,以花生粕为待测植物性饲料,配制半纯合试验日粮,花生粕和豆粕为磷唯一来源。日粮中添加0.35%Cr2O3作为外源指示剂。试验分6个试验期,每期8 d,6d适应期,2 d收粪期。结果表明,在以g/kg DMI为计量单位条件下,生长猪粪磷的排出量与日粮磷的摄入量呈线性关系(P=0.000 1),回归法测得生长猪内源磷的排泄量为0.526 6 g/kg DMI,花生粕磷的真消化率为28.00%,豆粕磷的真消化率为38.87%。分析粪磷来源发现,内源磷排泄量基本不变(P=0.13),而日粮来源粪磷随日粮含量的增加而增加(P=0.000 1),说明多重线性回归法可用于测定猪内源磷排泄量及非常规植物性饲料磷的真消化率;比较真消化率和表观消化率值说明,真消化率比表观消化率具有较好的重复性。     

二元线性回归法测定生长猪内源磷排泄量及麦麸和豆粕磷的真消化率

本研究采用二元线性回归法测定生长猪内源磷排泄量及麦麸和豆粕磷的真消化率.选用6头健康大白×长白阉公猪为试验动物,平均体重为(34.42±0.64)kg.采用6×6拉丁方设计,设6个总磷水平(0.12%、0.25%、0.28%、0.35%、0.47%和0.54%),日粮以豆粕、葡萄糖、玉米淀粉等为基础原料,麦麸和豆粕为磷来源.日粮中添加0.1%TiO2作为外源指示剂.试验分6个试验期,每期6 d,4 d适应期,2 d收粪期.结果表明,生长猪粪磷的排出量与日粮磷的摄入量呈线性关系(y=0.515 7x-0.0133,R2=0.97,P<0.01),回归法测得生长猪内源磷的排泄量为0.933 0g/kg,麦麸和豆粕磷的真消化率分别为48.07%和47.50%.分析粪磷来源发现,内源磷排泄量基本不变(P>0.05),而粪磷随日粮磷含量的增加而极显著增加(P<0.01).由结果可知,线性回归法可用于测定猪内源磷排泄量及麦麸和豆粕磷的真消化率.     

用线性回归法测定生长母猪内源钙、磷排泄量和豆粕钙、磷真消化率的研究

本文旨在用线性回归法(又称梯度回归法,regression analysis technique,REG)测定生长母猪钙、磷内源排泄和豆粕钙、磷真消化率。选择6头大白×长白二元杂交生长母猪,平均初始体重为(27.6±3.0)kg。采用6×6拉丁方设计,以玉米淀粉-豆粕为基础配制6个不同钙(0.04%、0.09%、0.13%、0.17%、0.22%和0.26%)和磷(0.09%、0.18%、0.27%、0.35%、0.44%和0.53%)水平的半纯合日粮,试验共6期,每期8d,预试期6d,正试期2d。结果得出,以日粮干物质采食量(DMI)为基础,粪钙的排泄量随日粮钙摄入量的增加而线性增加(P<0.01),用回归曲线法得出内源钙排泄量为0.43g/kg DMI,豆粕钙的真消化率为23.41%。以DMI为基础,粪磷总排泄量随日粮磷摄入量的增加而线性增加(P<0.01),内源磷排泄量为0.89g/kg DMI,豆粕磷真消化率为41.44%。钙平均表观消化率比真消化率低28.77%,磷平均表观消化率比真消化率低29.24%。结果显示,不同钙、磷水平的豆粕日粮,钙、磷的表观消化率变化比较大,而真消化率相对稳定。用表观消化率进行饲料配方,会导致钙、磷生物学效价的低估,造成钙、磷过量添加和猪粪钙、粪磷的增加。用真消化率评定钙、磷的生物学效价,比表观消化率更准确,因此在配制动物日粮时更能接近动物实际生产需要量,既不造成浪费也不会出现缺乏。     

用线性回归法测定生长猪内源钙、磷排泄量和豆粕钙、磷真消化率的研究

用线性回归法（Linear Regression Analysis Technique，REG）测定生长公猪内源钙、磷排泄量和豆粕钙、磷的真消化率。选用6头大白&#215;长白生长阉公猪为试验动物，平均初始体重为（28．6&#177;1．76）kg。采用6&#215;6拉丁方设计，以豆粕-玉米淀粉为基础，配制6个不同钙（0．04％、0．09％、0．13％、0．17％、0．22％、0．26％）、磷（0．09％、0．18％、0．27％、0．35％、0．44％、0．53％）水平的日粮。试验共6期，每期8d，预饲期6d，采样期2d。结果显示，以日粮干物质采食量（DMI）为基础，粪钙的排泄量随日粮钙的摄入量的增加而线性增加（P=0．002〈0．01），通过回归曲线法得出内源钙排泄量为0．6225g／kgDMI，豆粕钙真消化率为44．34％。以日粮干物质采食量（DMI）为基础，粪磷的排泄量随日粮磷的摄人量的增加而线性增加（P=0．025〈0．05），内源磷的排泄量为1．0771g／kgDMI，豆粕磷的真消化率为48．78％。结果表明，不同钙、磷水平的豆粕日粮，钙、磷的表观消化率变化较大，真消化率相对稳定。钙表观消化率平均比真消化率低41．50％，磷表观消化率平均比真消化率低35．51％。日粮配制时用钙、磷表观消化率会低估钙、磷生物学效价，造成钙、磷的过量添加和猪粪钙、粪磷排泄量的增加。因此，日粮配制时用钙、磷真消化率来评定钙、磷的生物学效价更精确。     

线性回归法测定生长猪内源磷排泄量及鱼粉磷真消化率

本研究采用线性回归法测定生长猪内源磷排泄量及鱼粉磷的真消化率.选用5头健康大白×长白阉公猪为试验动物,平均体重为(27.17±0.28)kg.采用5×5拉丁方设计,设5个磷水平(0.08%、0.12%、0.17%、0.21%和0.25%),日粮以葡萄糖和玉米淀粉等为基础原料,鱼粉为磷唯一来源.日粮中添加0.1%TiO2作为外源指示剂.试验分5个试验期,每期6 d,4 d适应期,2 d收粪期.结果表明,生长猪粪磷的排出量与日粮磷的摄入量呈线性关系(y=0.292 7x-0.052 8,R2=0.99,P<0.01),回归法测得生长猪内源磷的排泄量为0.798 5 g/kg,鱼粉磷的真消化率为71.12%.分析粪磷来源发现,内源磷排泄量基本不变(P>0.05),而粪磷随日粮磷含量的增加而增加(P<0.01).由结果可知,线性回归法可用于测定猪内源磷排泄量及鱼粉磷真消化率.     

磷的标准全肠道消化率和真消化率评定及其可加性研究

试验旨在比较使用磷的标准全肠道消化率(STTD)和真消化率(TPD)评定生长猪对玉米和豆粕中磷的利用效率及其是否具有可加性。选用56头平均体重为(30.5±0.8)kg的三元杂种去势公猪随机分为7个处理,每个处理8个重复,每个重复1头猪。对照组(无磷饲粮)用于测定猪的内源磷排泄量,6个试验饲粮按2×3因子试验设计,包含2个磷水平(低磷0.14%或高磷0.24%)和3种待测饲料原料(玉米、豆粕以及玉米豆粕混合物)。结果表明,随饲粮磷水平的提高,生长猪总磷日摄入量、粪磷日排泄量和日可消化磷均极显著增加(P0.01)。生长猪采食低磷饲粮和高磷饲粮测得玉米、豆粕以及玉米豆粕混合物中磷标准全肠道消化率(STTD)分别为42.06%和41.11%、48.73%和48.43%、44.38%和44.23%。低磷饲粮和高磷饲粮组玉米豆粕混合物中磷STTD计算值分别为44.28%和43.55%,与测定值44.38%和44.23%相比无显著差异(P0.05)。线性回归法测得玉米、豆粕以及玉米豆粕混合物磷的真消化率(TPD)为40.71%、49.83%和44.21%。玉米豆粕混合物TPD计算值为43.75%,与测定值44.21%相比差异不显著(P0.05)。由此可见,使用磷STTD和TPD用于生长猪玉米豆粕型饲粮配制时均具有较好的可加性。     

肉鸡饲粮钙磷比对豆粕中磷真消化率的影响

本试验旨在使用线性回归法和差量法研究肉鸡饲粮钙磷比对豆粕中磷真消化率的影响。选用576只15日龄罗氏肉鸡,根据3×3因子完全随机区组设计分为9个处理,每个处理8个重复,每个重复8只鸡。通过添加3个水平的豆粕(30.00%、43.00%和56.00%),研究饲粮钙磷比(1.0、1.5和2.0)对豆粕中磷真消化率测定值的影响。试验期7 d。结果表明:肉鸡体增重、饲料转化效率、回肠食糜磷排泄量和可消化磷均随豆粕水平提高呈线性增加(P0.01),而干物质消化率和磷的表观消化率呈线性降低(P0.01)。提高饲粮钙磷比可显著增加回肠食糜磷排泄量,从而降低可消化磷和磷的表观消化率(P0.01)。使用线性回归法和差量法在钙磷比为2.0时测得豆粕中磷的真消化率分别为40.79%和39.84%,显著低于钙磷比在1.0(53.36%和55.59%)和1.5(56.81%和56.36%)时测得磷的真消化率(P0.05)。由此可见,肉鸡饲粮钙磷比显著影响豆粕中磷真消化率的测定,但真消化率计算方法(线性回归法和差量法)对测定结果无显著影响。     

日粮磷水平对线性回归法测定磷真消化率的影响

本试验旨在研究日粮磷水平对线性回归法测定豆粕中磷真消化率的影响。选用48头平均体重为(36.0±0.1)kg生长公猪,采用2×3因子完全随机区组设计,随机分为6个处理,每个处理8个重复,每个重复1头猪。通过在半纯合日粮(低磷日粮,无玉米添加)和常规日粮(高磷日粮,含50.0%玉米)上添加3个水平豆粕(13.0%、26.0%和39.0%),研究日粮类型(低磷日粮和高磷日粮)对线性回归法测定豆粕中磷真消化率的影响。结果表明:随日粮豆粕水平增加,生长公猪的总磷摄入量、粪磷排泄量、可消化磷和存留磷量呈线性增加(P<0.01)。与低磷日粮相比,采食高磷日粮显著增加日粮总磷摄入量、粪磷排泄量、尿磷排泄量、可消化磷和存留磷(P<0.05)。通过使用线性回归法,生长猪采食高磷日粮测得豆粕中磷的真消化率为36.11%,显著低于采食低磷日粮测得结果 43.38%(P<0.05)。由此可见,由半纯合日粮(低磷日粮)测定得出的豆粕中磷的真消化率显著高于常规日粮(高磷日粮)的测定值,因此在使用半纯合日粮测得饲料原料中磷真消化率的数据用于日粮配置时应考虑上述因素。     

不同方法测定生长猪内源磷排泄量及磷真消化率的比较研究

采用梯度回归法(REG法)和差量法,用豆粕和次粉作为日粮磷唯一来源,分别设计了 2 组总磷(TP)水平为0 .15%、0. 20%、0. 30%、0. 35%梯度饲粮,按4×4拉丁方设计,测定了20 kg生长猪内源磷排泄量和豆粕、次粉磷的真消化率。结果表明,在0 .15%~0 .35%TP水平范围,粪磷的排泄量与磷摄入量之间存在明显的线性关系,动物具有稳定的内源磷排泄量。不同饲料条件下REG法测定的内源磷排泄量与差量法测定结果无显著差异(P>0. 05),2种方法测定内源磷排泄量都是可行的;生长猪内源磷排泄量为0. 65~0. 68 g/kg DMI;次粉磷的真消化率显著高于豆粕(P<0. 01),分别为63.7%和52.1%。     

生长猪基础饲粮组成对磷酸氢钙和磷酸二氢钙中磷的全肠道真消化率的影响

本试验旨在研究生长猪基础饲粮组成对磷酸氢钙(DCP)和磷酸二氢钙(MCP)中磷的全肠道真消化率(TTTD)的影响。试验1选用10头平均体重为(30.4±1.8)kg的生长猪,按照10×8不完全拉丁方设计,分别饲喂含有5个DCP添加水平的玉米-豆粕型和含有5个DCP添加水平的小麦-豆粕型饲粮,进行8期消化试验;试验2选用10头平均体重为(30.9±1.5)kg的生长猪,按照10×8不完全拉丁方设计,分别饲喂含有5个M CP添加水平的玉米-豆粕型和含有5个MCP添加水平的小麦-豆粕型饲粮,进行8期消化试验。每期消化试验包括5 d的饲粮适应期和2 d的粪便收集期。结果表明:1)玉米-豆粕型饲粮的总粪磷排泄量极显著高于小麦-豆粕型饲粮(P0.01),小麦-豆粕型饲粮的全肠道可消化磷含量和磷的表观全肠道消化率(ATTD)极显著高于玉米-豆粕型饲粮(P0.01)。饲粮添加DCP和MCP线性增加总粪磷排泄量、全肠道可消化磷含量及磷的ATTD(P0.01)。2)通过使用线性回归法,测得生长猪采食玉米-豆粕型和小麦-豆粕型饲粮对DCP中磷的TTTD分别为82.33%和82.88%,生长猪采食玉米-豆粕型和小麦-豆粕型饲粮对MCP中磷的TTTD分别为85.88%和84.62%。由此可见,生长猪基础饲粮组成对DCP和MCP中磷的TTTD无显著影响。     

Determination of true digestive utilization of phosphorus and the endogenous phosphorus outputs associated with soybean meal for growing pigs

The objectives of this study were to determine true P digestibility, the gastrointestinal endogenous P outputs associated with soybean meal (SBM), and the role of the large intestine in P digestion in growing pigs. Four Yorkshire barrows, with average initial and final BW of 40 and 58 kg, were fitted with a simple T-cannula at the distal ileum and fed four diets according to a 4 x 4 Latin square design. The diets were cornstarch-based and contained four levels of P (0.098, 0.196, 0.293, and 0.391% on a DM basis) from solvent-extracted conventional SBM. Chromic oxide (3.5 g/kg of diet, as-fed basis) was included as a digestibility marker. Each experimental period consisted of 8 d with a 4-d adaptation period and a 4-d collection of representative ileal digesta (2 d) and fecal (2 d) samples. True ileal and fecal P digestibility values and the ileal and fecal endogenous P outputs associated with SBM were determined by the regression analysis technique. There were no differences (P > 0.05) in true P digestibility values (ileal, 59.0 +/- 8.3 vs. fecal, 51.3 +/- 7.9%, n = 16) and endogenous P outputs (ileal, 0.59 +/- 0.18 vs. fecal, 0.45 +/- 0.21 g/kg of DMI, n = 16) between the ileal and the fecal levels. The endogenous fecal P loss accounted for 8.1 and 17.6% of the NRC (1998) recommended total and available P requirements in growing pigs, respectively. In conclusion, approximately 51% of the total P in conventional SBM is digested in growing pigs. The large intestine does not play an important role in the digestion of P associated with SBM in the growing pig. The fecal loss of the gastrointestinal endogenous P is an important route of P excretion in the growing pig.     

Effects of level of supplemental phytase on ileal digestibility of amino acids, calcium, and phosphorus in dehulled soybean meal for growing pigs.

Ileally cannulated pigs were used to assess the effects of four dietary levels of microbial phytase (Natuphos) on the apparent and true digestibility of Ca, P, CP, and AA in dehulled soybean meal. Fourteen pigs (25 kg initial BW) were surgically fitted with T-cannulas at the terminal ileum and assigned to diets in a replicated 7 x 7 Latin square design. Following a 14-d recovery, four diets consisting of 30.5% soybean meal with 0, 500, 1,000, or 1,500 units of phytase/kg of diet were fed. Diets 5 (1.05% lysine, 0.90% Ca, and 0.75% P) and 6 (1.05% lysine, 0.90% Ca, and 0.75% P) contained 35.25% soybean meal and 27.0% soy protein concentrate, respectively. Diet 7 (0.37% lysine, 0.03% Ca, and 0.05% P) was a low-CP, casein-based diet used to estimate the nonspecific endogenous losses of Ca, P, CP, and AA in order to estimate the true digestibility of these nutrients. All diets contained cornstarch and dextrose and were fortified with vitamins and minerals. Chromic oxide was used as an indigestible indicator. The diets were fed daily at 9% of metabolic BW (BW0.75). Apparent and true ileal digestibility of P increased quadratically (P < 0.01) and true digestibility of Ca increased linearly (P < 0.07) with increasing levels of phytase. Apparent digestibility of Ca was unaffected (P = 0.15) by phytase level. Apparent and true ileal digestibility of CP and most AA increased slightly with the addition of 500 units of phytase/kg of diet, but not at higher levels of phytase supplementation (in most cases, cubic effect, P < 0.05). Apparent and true ileal nutrient digestibility coefficients were unaffected by soybean meal source (Diet 1 vs Diet 5), except for arginine and Ca. The apparent and true digestibility coefficients for most of the AA tended (P < 0.10) to be lower in diets containing soy protein concentrate vs the common source of soybean meal used in Diet 5, but ileal digestibilities of Ca and P were unaffected (P = 0.15). In this study, supplemental microbial phytase did not improve the utilization of AA provided by soybean meal but was an effective means of improving Ca and P utilization by growing swine fed soybean meal-based diets.     

Amino acid digestibility in dry extruded-expelled soybean meal fed to pigs and poultry

The digestibility of AA in dry extruded-expelled soybean meal (DESBM) and regular, solvent-extracted soybean meal (SBM) were determined in pigs and poultry. In the pig assay, 4 Cotswold barrows (average initial BW of 80.4 kg) fitted with a T-cannula at the distal ileum were allotted to 4 semipurified diets in a 4 x 4 Latin square design. Diet 1, a low protein diet (5% casein), was used to quantify endogenous CP and AA losses. Diets 2, 3, and 4 were formulated to contain 35% regular, solvent-extracted SBM; batch 1 of DESBM (DESBM-1); and batch 2 of DESBM (DESBM-2), respectively, as the sole source of protein. The DESBM samples were obtained from 2 different batches but were subjected to the same processing conditions. Chromic oxide (0.3%) was included as a digestibility marker in all diets. Compared with DESBM-1 and DESBM-2, apparent ileal digestibility of DM in SBM was greater (P < 0.05). Apparent and true ileal digestibilities of AA in SBM were greater (P < 0.05) compared with DESBM-2. In the poultry assay, 4 dietary treatments were each assigned to adult cecectomized roosters in a completely randomized design. Treatment 1 was a nonnitrogenous diet (NND; 90% sucrose and 10% vegetable oil) used to estimate endogenous N and AA losses. Treatments 2, 3, and 4 contained SBM, DESBM-1, and DESBM-2 as the only source of protein. Each of these diets was fed in 25-g quantities formulated to provide 5 g of CP from the respective soybean meal source. The SBM had greater (P < or = 0.05) true digestibility for isoleucine, leucine, cysteine, proline, serine, and tyrosine compared with DESBM-1. The results indicate that, relative to regular, solvent-extracted soybean meal, AA digestibilities of different batches of dry extruded-expelled soybean meal varied in pigs and poultry.     

Digestibility of phosphorus in growing pigs as influenced by source and concentration of dietary phosphorus and collection site

The current study examined the influence of source and concentration of dietary phosphorus (P) on the apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of P in growing pigs. Eighteen cannulated barrows (25 ± 5 kg) were allotted to a triplicate 6 × 3 incomplete Latin square design with six diets and three periods. The diets comprised of soybean meal (SBM) or distillers' dried grain with solubles ( DDGS) as sole sources of dietary P, and three concentrations of P (2.0, 2.5 or 3.0 g/kg) in a 2 × 3 factorial arrangement. The AID and ATTD of P were not different (p = 0.37) in all diets. Apparent digestibility of P was affected (p < 0.01) by source and concentration of P. There was no interaction between source and concentration of dietary P on the apparent digestibility of P. Determined by regression analysis, the true ileal digestibility of P was 58.3% or 57.6%, and true total tract digestibility of P was 56.0% or 62.6%, for SBM or DDGS, respectively. The regression-derived ileal endogenous P loss (EPL) was 0.61 or 0.13 g/kg DM intake, and total tract EPL was 0.53 or 0.35 g/kg DM intake, for SBM or DDGS, respectively. In conclusion, the study demonstrated that both the source and concentration of dietary P affect the digestibility of P in growing pigs.     

A Comparative Study of the Difference Method and the Enzyme-Hydrolyzed Casein Method for Determining True Amino Acid Digestibilities and Endogenous Amino Acid Losses in Duck Feed

In this study,we examined the variations between the difference method and the enzyme-hydrolyzed casein method for determining endogenous amino acid loss and the true amino acid digestibility in ducks fed normal protein-containing diets.These methods were compared to the nitrogen-free(N-free)diet method.The difference method was based on soybean meal as the only protein source,with the experimental diets containing crude protein levels at 15% and 20%.The enzyme-hydrolyzed casein method was based on enzyme-hydrolyzed casein meal as the protein source,with the experimental diet containing a crude protein level of 17.5%.The N-free diet was prepared with starches and paper fibers.In each method,64 Tianfu meat drakes(7-weeks-old)with an average body weight of 2.77±0.16 kg were used and divided into four groups,and fed four different diets.Each group contained four replicates of four drakes and they were force fed trial diets according to the Sirbald method for detecting their apparent amino acid digestibility,endogenous amino acid loss and true amino acid digestibility.The results demonstrated that using the difference,enzyme-hydrolyzed casein and N-free diet methods,endogenous amino acid losses were 0.9946,1.2243 and 0.9297 mg/g dry matter intake(DMI),respectively.The true amino acid digestibility measured by the difference method was 88.93%±4.43%.Using the enzyme-hydrolyzed casein method with two dietary crude protein levels of 15% and 20%,the digestibility was 91.15%±4.33% and 91.97%±4.16%,respectively,and by the N-free diet methods with two dietary crude protein levels of 15% and 20%,it was 88.55%±4.29% and 88.82%±4.61%,respectively.The results suggested that when the dietary protein level was 15% to 20 %,the true amino acid digestibility and endogenous amino acid loss as determined by the difference method was more accurate than the values determined by the enzyme-hydrolyzed casein method.     

低磷日粮对生长猪生产性能、养分消化率和经济效益的影响

选用288头体重26kg左右、体质健康的杜×长×大三元杂交生长猪,随机分为两组,每组三个重复,以玉米-豆粕-小麦型为基础日粮,对照组日粮参照NRC(1998)标准设计,试验组日粮添加0.33%的磷酸氢钙,且日粮的有效磷(AP)水平为0.205%。试验期30d。研究了低磷日粮对生长猪的生长性能、养分利用及其对环境的影响。结果表明:在不影响猪磷营养需要的条件下,能有效的改善猪排泄物中磷对环境的污染,具有极大的经济和生态效益。     

Estimation of true phosphorus digestibility and endogenous phosphorus loss in growing pigs fed conventional and low-phytate soybean meals

This study reevaluated the method of regressing of total P output against dietary P intake to simultaneously estimate true P digestibility and endogenous P loss in growing pigs fed either conventional or low-phytate soybean meal (SBM). Four isocaloric diets were formulated to contain increasing concentrations of each type of SBM (8 diets total), and therefore contained increasing concentrations of dietary P. Dietary P and Ca concentrations were deficient because they were supplied solely by SBM, and Ca:total P ratios were less than 1:1. Sixteen barrows (initial BW 17.7 +/- 1.8 kg) were surgically fitted with a simple T-cannula at the distal ileum, randomly assigned to metabolism crates, and fed the experimental diets in a replicated 8 x 8 Latin square design. Feed was provided at 90 g/kg of BW(0.75) and fed in 2 equally sized meals at 0800 and 2000, with diets containing Cr sesquioxide (3 g/kg) as an indigestible marker. As the P concentration increased from 0.9 to 3.9 g/kg of DM, the apparent prececal P digestibility increased for conventional SBM (P < 0.05), but no relationship was observed for low-phytate SBM. The output of total P [mg/(kg of BW(0.75).d)], either prececal or total tract, exhibited a linear relationship (P < 0.01) with increasing P intake. However, a quadratic response (P = 0.02) was also detected for total tract P output from pigs fed low-phytate SBM. True P digestibility was not different between prececal and total tract collection sites (P > 0.10), but was greater (P < 0.01) for low-phytate SBM (62.6%) compared with conventional SBM (44.5%). Endogenous P estimates were not different between the SBM varieties and averaged 4.83 mg/(kg of BW(0.75).d). However, endogenous P estimates were highly variable between individual animals and, therefore, were not significantly different from zero. In this study, estimates of endogenous P loss from pigs were relatively low compared with previously reported values, and evidence of nonlinearity in P output was observed. These results suggest that the difference in true P digestibility between conventional SBM and low-phytate SBM is influenced by dietary phytate content when growing pigs are fed P-deficient diets.