Abstract
Standardized ileal digestibility coefficients(SIDC)of nitrogen(N)and amino acids(AA)in two protein sources(soybean meal[SBM]and canola meal[CM])were investigated at six broiler ages(d 7,14,21,28,35,and 42).Two assay diets were formulated to contain either SBM(413 g/kg)or CM(553 g/kg)as the sole dietary AA source.Titanium dioxide(5 g/kg)was added as an indigestible marker.A total of 696 male broilers at 1 d old were allotted to 12 replicate cages per age group.Each assay diet was offered to birds for 4 d prior to the ileal digesta collection on d 7(14 birds/cage),14(12 birds/cage),21(10 birds/cage),28(8 birds/cage),35(8 birds/cage)and 42(6 birds/cage),respectively.The apparent digestibility coefficients were standardized using age-specific basal endogenous AA flows.In the SBM group,though the SIDC of N tended to be influenced(quadratic;P=0.075)by age,no linear or quadratic response of age effect was observed on the average SIDC of indispensable(IAA)and total AA(TAA).An age effect(quadratic;P＜0.05)was observed on the average SIDC of dispensable AA(DAA)in SBM with the highest value recorded at d 7,followed by a decrease from d 14 to 28,which increased beyond d 35.The SIDC of some individual AA(Arg,Thr,Trp,Cys,Pro)were affected(P＜0.05 or P＜0.001)in a quadratic manner by age.In the CM,the SIDC of N,average SIDC of IAA,DAA and TAA were influenced(quadratic;P＜0.05 or P＜0.001)by age.The SIDC of N and average SIDC of DAA and TAA were higher from d 7 to 14,declined at d 21,and then increased beyond d 28.The average SIDC of IAA was low between d 7 and 28 and increased thereafter.The SIDC of individual AA were affected(linear or quadratic;P＜0.05 or P＜0.001)by different magnitudes by age.The age influence on the SIDC AA was variable,depending on the protein source and AA.The results demonstrate that age-specific SIDC AA data might need consideration in broiler feed formulations.
基金项目
AgriFutures Australia Chicken Meat Program(PRJ-011835)
NETL
NSTL
万方数据