本试验旨在研究不同蛋白质水平的饲粮对银黑狐生长性能、血清生化指标及氮代谢的影响。选取60只9周龄、体重为(3 371.25±527.16) g健康的雄性银黑狐,随机分为5组,每组12个重复,每个重复1只,各组分别饲喂蛋白质水平为37.83%、35.54%、33.22%、30.10%和22.70%的饲粮。预试期12 d,正试期45 d。记录体重、采食量的变化;正试期第25~27天进行消化代谢试验,收集饲粮样、粪样和尿样,测定氮含量;正试期第31天采集血样,测定血清白蛋白含量、碱性磷酸酶活性以及尿素氮和总胆固醇浓度。结果表明:1)饲粮蛋白质水平对银黑狐的体重、平均日增重有显著影响(P<0.05),饲粮蛋白质水平为37.83%时,银黑狐第31天体重、末重均显著高于饲粮蛋白质水平为22.70%时(P<0.05)。2)饲粮蛋白质水平对银黑狐血清尿素氮浓度及碱性磷酸酶活性影响显著(P<0.05),随饲粮蛋白质水平的降低,血清碱性磷酸酶活性先降低后升高,血清尿素氮趋势相反。3)饲粮蛋白质水平对摄入氮、尿氮、氮表观消化率、沉积氮、氮的沉积率有显著影响(P<0.05);随饲粮蛋白质水平的降低,氮表观消化率、氮沉积、氮沉积率均呈现下降趋势;各组排出氮量差异不显著(P>0.05),饲粮蛋白质水平22.70%、33.22%时较低,37.83%时最高。结果提示,饲粮蛋白质水平从37.83%降到30.10%对银黑狐的生长性能并没有影响,从降低环境的污染和保证银黑狐生长性能的角度出发,33.22%为较适宜的饲粮蛋白质水平。

This experiment was conducted to study the effects of dietary protein levels on growth performance, serum biochemical indices and nitrogen metabolism of silver foxes. Sixty male silver foxes aged 9 weeks with a similar body weight were randomly divided into 5 groups with 12 replicates per group and 1 fox per replicate, and they were fed diets containing 37.83%, 35.54%, 33.22%, 30.10% and 22.70% protein, respectively. The pre-trail period lasted for 12 d, and the trial period lasted for 45 d. Changes of body weight and feed intake were recorded; digestion and metabolism trials were carried out from the 25th to 27th day of the trial period, and samples of feed, fecal and urine were collected to determine nitrogen content; on the 31st day, blood sample was collected for analysis of serum albumin content, alkaline phosphatase activity, as well as concentrations of urea nitrogen and total cholesterol. The results showed as follows: 1) dietary protein levels had significant effects on body weight and average daily gain (P<0.05); the body weight on the 31st day and the final of foxes fed diet with protein level of 37.83% was significantly higher than that of foxes fed diet with 22.70% protein (P<0.05). 2) Dietary protein levels had significant effects on serum urea nitrogen concentration and alkaline phosphatase activity (P<0.05); with the decrease of dietary protein level, serum alkaline phosphatase activity tended to decrease at first and then increase, while serum urea nitrogen concentration acted as an opposite tend. 3) Dietary protein levels had significant effects on nitrogen intake, urea nitrogen, nitrogen apparent digestibility, nitrogen retention and nitrogen retention ration (P<0.05); nitrogen apparent digestibility, nitrogen retention and nitrogen retention ration levels tended to decline with dietary protein level decreased; there were no significant differences in nitrogen excretion among groups (P>0.05), the values of nitrogen excretion in 22.70% and 33.22% protein groups were lower, and that in 37.83% protein group was the highest. These results indicate that dietary protein levels can be reduced to 30.10% from 37.83% without negative effects on growth performance of foxe, and the 33.22% is considered to be an optimal protein level with lower environmental pollution and maintained growth performance.