Digestible and metabolizable energy concentrations and amino acid digestibility of dried yeast and soybean meal for growing pigs

Energy values and amino acid (AA) digestibility of dried yeast (DY) and soybean meal (SBM) were determined in 2 experiments with growing pigs. Experiment 1 was conducted to determine the digestible energy (DE) and metabolizable energy (ME) in DY and SBM. Thirty barrows with a mean initial body weight (BW) of 20.6 kg (SD = 1.04) were assigned to 5 dietary treatments in a randomized complete block design with period and BW as blocking factors. A reference diet was prepared with corn, canola meal, and soybean oil as energy-contributing ingredients. Four additional diets were prepared by adding 5% and 10% DY or SBM at the expense of energy-contributing ingredients in the reference diet. The ratio of corn, canola meal, and soybean oil was kept consistent across the experimental diets. Each experimental period consisted of 5-d adaptation and 5-d quantitative collection of feces and urine. Test ingredient-associated DE or ME intake (kcal/d) was regressed against test ingredient intake [kg dry matter (DM)/d] to estimate the DE or ME in test ingredients as the slope of linear regression model. The DE in DY was estimated at 3,933 kcal/kg DM, which was not different from the estimated DE in SBM at 4,020 kcal/kg DM. Similarly, there was no difference between DY and SBM in the estimated ME (3,431 and 3,756 kcal/kg DM, respectively). Experiment 2 was conducted to determine the standardized ileal digestibility (SID) of AA in DY and SBM. Twenty-one barrows with a mean initial BW of 20.0 kg (SD = 1.31) were surgically fitted with T-cannulas at the distal ileum and assigned to 3 dietary treatments in a randomized complete block design with BW as a blocking factor. Two semi-purified diets containing DY or SBM as the sole nitrogen source and one nitrogen-free diet (NFD) were prepared. The NFD was used to estimate the basal ileal endogenous losses of CP and AA. Pigs were fed the 3 diets for 5 d as adaptation, followed by 2 d of feeding with ileal digesta collection. The SID of AA, except Gly and Pro, in DY was less (P < 0.05) than in SBM. The SID of indispensable AA in DY ranged from 64.1% for Thr to 85.2% for Arg, and those in SBM ranged from 83.9% for Thr to 91.8% for Arg. In conclusion, energy values of DY are not different from those of SBM, whereas AA in DY is less digestible than in SBM. The estimated DE and ME as well as the SID of AA in DY and SBM can be used in diet formulation for growing pigs using these ingredients.     

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.     

Yield improvement in maize for tolerance to low soil nitrogen

Low soil nitrogen limits maize (Zea mays L.) production in the West and Central African subregion. Levels of residual genetic variability were determined in two low‐N populations using selfed progeny evaluations, and results obtained indicate large genotypic and phenotypic variances for grain yield under both low‐ and high‐N environments for effective selection, while heritability estimates were generally low. Ear aspect and stay green were the most important traits contributing to grain yield for both populations. Selection reduced days to flowering, ASI and ear aspect, but increased plant height and yield. Yield gains of more than 25% occurred for the two populations under both low and high N with the most significant change of 42% occurring in one population under high N.     

Assessment of heterotic patterns of tropical low-nitrogen–tolerant maize (Zea mays L.) inbred lines using testcross performance,morphological traits and SNP markers

Breeding efforts in West and Central Africa (WCA) have focused on the development of Low-N-tolerant (LNT) maize inbreds and their classification into heterotic groups. This study was conducted to classify LNT maize lines into heterotic groups using testcross performance, morphological and SNP markers and to compare the consistency of groupings by the three methods. Thirty-six LNT inbreds were crossed to two contrasting inbred testers to generate 72 testcrosses that were evaluated under low-N conditions in Nigeria in 2014. Also, the 36 inbreds and the two testers were evaluated for per se performance under similar conditions as the testcrosses in 2014 and genotyped in 2015 using 1,123,196 SNP markers. Based on testcross performance, 33 of the 36 LNT inbreds were grouped by the two testers. Morphological characterization from per se performance and genetic relationship by SNP markers classified the inbreds into four groups that were inconsistent with their pedigree. Correlation analysis showed non-concurrence of the three grouping methods. However, information from these groupings would assist in reducing the number of crosses to be made and evaluated.     

Water-soluble phosphorus excretion in pigs fed diets supplemented with microbial phytase

Three experiments were conducted to compare the excretion of water-soluble phosphorus (P) of starter, grower, and finisher pigs fed corn-soybean meal-based P-deficient basal diet containing no added inorganic P (B), P-adequate diet (the basal diet with added dicalcium phosphate; B + P), the basal diet plus 500 units of microbial phytase/kg (B + 500), or the basal diet plus 1000 units of microbial phytase/kg (B + 1000). There were 6 barrows per diet, in a randomized complete block design, with an average initial body weight of 10.4, 20.0, or 51.1 kg for each of starter, grower, and finisher pigs in the three phosphorus balance experiments, respectively. In the experiments, the addition of dicalcium phosphate or phytase to the basal diet increased ( P  < 0.05) the digestibility and retention of P, and there were linear reductions ( P  < 0.05) in water-soluble P excretion as a result of supplementing the basal diet with phytase. In the starter pig experiment, phytase addition at 500 or 1000 units/kg reduced ( P  < 0.05) water-soluble P excretion by 28 or 42%, respectively when compared with the B + P diet. In the grower pig experiment, adding phytase at 500 or 1000 units/kg reduced ( P  < 0.05) water-soluble P excretion by 24 or 34%, respectively when compared with the B + P diet. The use of phytase at 500 or 1000 units/kg reduced ( P  < 0.05) water-soluble P excretion by 11 or 30%, respectively in the finisher pig experiment. The proportion of water-soluble phosphorus in total phosphorus was not affected by dietary treatment in any of the three experiments. In conclusion, adding phytase at 1000 units/kg to a corn-soybean meal-based P-deficient diet basal diet containing no added inorganic P compared with B + P diet reduced the daily excretion of water-soluble P in starter, grower, and finisher pigs by 42, 34, and 30%, respectively.     

回归分析法评价4种麦类饲料原料的肉鸡有效能值

本试验旨在评价大麦、黑小麦、小麦和黑麦4种麦类饲料原料在肉鸡上的有效能值,以期优化现有配方数据库,逐步实现饲粮营养的精准供给。采用回归分析法,试验分2批进行,试验1评价大麦和黑小麦的肉鸡回肠消化能(IDE)、代谢能(ME)、氮校正代谢能(MEn),试验2评价小麦和黑麦的肉鸡IDE、ME、MEn。每个批次试验均选用320只1日龄雄性罗斯708肉鸡为试验动物,将其随机分为5个组,每组设8个重复,每个重复8只鸡。1~20日龄为预试期,饲喂基础饲粮;21~28日龄为试验期,分别饲喂基础饲粮和试验饲粮。试验1的5个组21~28日龄所喂饲粮如下:基础饲粮、含250 g/kg大麦的饲粮、含500 g/kg大麦的饲粮、含250 g/kg黑小麦的饲粮、含500 g/kg黑小麦的饲粮。试验2的5个组21~28日龄所喂饲粮如下:基础饲粮、含250 g/kg小麦的饲粮、含500 g/kg小麦的饲粮、含250 g/kg黑麦的饲粮、含500 g/kg黑麦的饲粮。结果表明:在饲粮中添加大麦、黑小麦、小麦和黑麦对肉鸡生长性能均无显著影响(P>0.05)。大麦替代量与干物质、能量的回肠消化率以及干物质、氮、能量的全肠道代谢率,以及IDE、ME、MEn存在极显著的线性降低关系(P<0.01);黑小麦替代量与氮全肠道代谢率、IDE、ME、MEn存在极显著的线性降低关系(P<0.01),且与干物质、能量回肠消化率、IDE存在显著或极显著的二次曲线关系(P<0.05或P<0.01);小麦替代量与干物质、氮、能量、氮校正能量的全肠道代谢率显著或极显著的线性降低关系(P<0.05或P<0.01),且与干物质、能量的回肠消化率和IDE存在显著或极显著的二次曲线关系(P<0.05或P<0.01);黑麦替代量与干物质、能量的回肠消化率以及干物质、氮的全肠道代谢率存在显著或极显著线性降低关系(P<0.05或P<0.01);且与干物质、能量的回肠消化率和干物质、氮、能量、氮校正代谢能的全肠道代谢率以及IDE、ME、MEn存在显著或极显著的二次曲线关系(P<0.05或P<0.01)。通过回归分析得出大麦的肉鸡IDE、ME和MEn分别为9.31、10.50、10.29 MJ/kg,黑小麦分别为10.99、11.80、11.43 MJ/kg,小麦分别为10.59、11.81、11.28 MJ/kg,黑麦分别为11.97、12.56、11.83 MJ/kg。