本试验旨在研究饲粮蛋白质水平对生长獭兔生长性能、氮代谢、小肠蛋白酶活性、血清生化指标以及血清激素指标的影响。选用平均体重为(620±30) g的断奶仔獭兔200只,随机分为5组(每组40个重复,每个重复1只),分别饲喂蛋白质水平为14.5%、16.0%、17.5%、19.0%、20.5%的试验饲粮,预试期为7 d,正试期为53 d。结果表明:饲粮蛋白质水平对平均日采食量、平均日增重、料重比、食入氮、沉积氮和可消化氮有显著或极显著影响(P<0.05或P<0.01),对粪氮、尿氮、氮表观消化率、氮生物利用率和氮利用率无显著影响(P>0.05)。饲粮蛋白质水平除显著影响血清球蛋白含量(P<0.05)外,对其他血清生化指标(总蛋白、白蛋白、胆固醇、尿素氮含量以及白球比)的影响不显著(P>0.05)。此外,饲粮蛋白质水平对小肠糜蛋白酶和胰蛋白酶活性以及血清生长激素、胰岛素和胰岛素样生长因子-1水平亦无显著影响(P>0.05)。由此得出,饲粮适宜的蛋白质水平能提高生长獭兔的平均日增重、平均日采食量,并能降低料重比,提高氮的利用效率,但对小肠蛋白酶活性以及血清指标的影响不大。以料重比、沉积氮为衡量指标,通过非线性回归模型估测得出生长獭兔饲粮适宜蛋白质水平分别为18.51%和19.45%。

This experiment was conducted to research the effects of dietary protein level on growth performance, nitrogen metabolism, protease activities in intestine, serum biochemical indices and serum hormone indices of growing Rex rabbits. Two hundred weanling Rex rabbits with an average body weight of (620?30) g were randomly divided into 5 groups with 40 replicates in each group and each replicate contained 1 rabbit. Rabbits in the 5 groups were fed experimental diets containing 14.5%, 16.0%, 17.5%, 19.0% and 20.5% protein, respectively. The experiment included a pretrial period of 7 days and an experimental period of 53 days. The results showed as follows: dietary protein level had significant influence on average daily gain, average daily feed intake, feed/gain, nitrogen intake, nitrogen retention and digestible nitrogen (P<0.05 or P<0.01), but had no significant influence on fecal nitrogen, urine nitrogen, nitrogen apparent digestibility, nitrogen bioavailability and nitrogen utilization rate (P>0.05). Dietary protein level significantly affected serum globulin content (P<0.05), while did not significantly affect other serum biochemical indices, including the contents of total protein, albumin, cholesterol and urea nitrogen, and albumin/globulin (P>0.05). Otherwise, the activities of trypsinase and chymotrypsin in intestine, and levels of growth hormone, insulin and insulin-like growth factor-1 (IGF-1) in serum were not significantly affected by dietary protein level (P>0.05). The results indicate that dietary optimal protein level can improve average daily gain, average daily feed intake and nitrogen utilization rate, and reduced the feed/gain, but has little effects on intestinal protease activities and serum indices. Based on the feed/gain and nitrogen retention, the dietary optimal protein level estimated by nonlinear regression model are 18.51% and 19.45%, respectively.