差量法和酶解酪蛋白法测定鸭饲料氨基酸真消化率及内源排泄量的比较研究

Comparison of Difference Method and Enzyme-hydrolyzed Casein Method for Determining True Amino Acids Digestibility and Endogenous Amino Acids Losses of Drakes

本试验研究了差量法和酶解酪蛋白法测定动物在采食正常含氮日粮条件下的内源氨基酸排泄量及饲料氨基酸真消化率的差异,并同时与无氮日粮法作比较。差量法以豆粕为唯一蛋白源,配制成15%和20%2种粗蛋白质水平的试粮;酶解酪蛋白法以酶解酪蛋白作为蛋白质来源,配制成17.5%粗蛋白质水平的试粮;无氮日粮用淀粉和纸纤维进行配制。每种方法选用7周龄、平均体重(2.77±0.16)kg天府肉公鸭64只,分为4组,分别饲喂4种不同日粮,每组4个重复,每重复4只鸭,采用Sibbald的强饲法进行代谢试验,测定各试粮氨基酸表观消化率、内源氨基酸排泄量及真消化率。结果显示:差量法、酶解酪蛋白法和无氮日粮法测定的内源氨基酸排泄量分别为0.9946、1.2243和0.9297mg/gDMI;差量法测定的氨基酸真消化率(%)为88.93±4.43,用酶解酪蛋白法和无氮日粮法测定的内源氨基酸排泄量计算的15%和20%2个粗蛋白质水平日粮氨基酸真消化率(%)分别为91.15±4.33和91.97±4.16、88.55±4.29和88.82±4.61。以上结果表明,在15%～20%的日粮蛋白质水平范围,差量法测定的氨基酸真消化率和内源氨基酸排泄量较酶解酪蛋白法准确,酶解酪蛋白法可能高估了内源氨基酸排泄量和氨基酸真消化率。

The experiment was designed to study the difference of enzyme-hydrolyzed casein （EHC） method and difference method （DF） for determining true amino acids digestibility （TAAAs） and endogenous amino acids losses （EAALs） of animal fed on normal protein-containing diets, and they were compared with the non-protein diets method. Difference method was conducted based on soybean-meal with two crude protein （CP） levels of 15% and 20%.enzyme-hydrolyzed casein method was conducted based on enzyme-hydrolyzed casein-meal with CP level of 17.5%. non-protein diets （NFD） method was con- ducted based on starch and paper fiber. In each method, sixteen 7-week-old tianfu meat-type drakes, with an average initial body weight of （2.76 ±0.17） kg, were allotted to 4 replicates of 4 drakes per replicate. Drakes were force-fed trial diets according to Sibbald method and the excreta were collected to determine AAAs, TAAAs and EAALs of drakes in each experimental diet. The results showed that EAALs measured by DF in the two dietary CP levels （15% and 20%） were 0.992 0 and 0.929 7 mg/g DMI, and the mean of them was 0.994 6 mg/g DMI. EAALs measured by EHC and NFD were 1.224 3 and 0. 929 7 mg/g D MI. TAAAs measured by DF was （88.81 ± 4.53）%, by EHC in the two dietary CP levels （15% and 20%） were （91.56±4.22）% and （91.97± 4.16）%, and by NFD in the two dietary CP levels （15% and 20%） were （88.55 ± 4.29） % and （88.82 ± 4.61）%. In conclusion, among 10%--20% dietary CP levels, TAAAs and EAALs of drakes determined by difference method could be more accurate than that determined by EHC. TAAAs and EAALs were overestimated by the method of EHC.