本试验旨在研究低蛋白质饲粮中添加蛋氨酸对育成期蓝狐生长性能、营养物质消化代谢的影响。选用平均体重为(2.21±0.60) kg的9周龄健康雄性蓝狐105只,随机分为7组,每组15个重复,每个重复1只。6个试验组分别饲喂在蛋白质水平为30％的基础饲粮(低蛋白质饲粮)中添加0(Ⅰ组)、0.2％(Ⅱ组)、0.4％(Ⅲ组)、0.6％(Ⅳ组)、0.8％(Ⅴ组)和1.0％(Ⅵ组)蛋氨酸的试验试粮。对照组(Ⅶ组)饲喂蛋白质水平为32％的基础饲粮(适宜蛋白质饲粮)。预试期7 d,正试期45 d。结果表明:Ⅴ组与Ⅵ组的末重(第45天体重)极显著高于其他试验组(P<0.01),并与对照组差异不显著(P>0.05)。第16~30天的平均日增重,Ⅳ组、Ⅴ组、Ⅵ组显著高于Ⅰ组(P<0.05),并与对照组差异不显著(P>0.05);第31~45天的平均日增重,Ⅴ组、Ⅵ组极显著高于其他试验组(P<0.01),且Ⅴ组还显著高于Ⅵ组和对照组(P<0.05)。Ⅴ组、Ⅵ组的干物质排出量极显著低于其他试验组(P<0.01),并与对照组差异不显著(P>0.05);Ⅴ组的干物质消化率显著高于Ⅰ组、Ⅲ组和Ⅳ组(P<0.05),并与对照组差异不显著(P>0.05);Ⅴ组、Ⅵ组的蛋白质消化率显著高于Ⅰ组、Ⅱ组和Ⅲ组(P<0.05),并与对照组差异不显著(P>0.05);Ⅰ组的脂肪消化率显著低于其他各组(P<0.05),其他各组间差异不显著(P>0.05)。Ⅴ组和Ⅵ组的胱氨酸排出量极显著低于Ⅱ组、Ⅲ组和对照组(P<0.01);Ⅵ组的胱氨酸消化率极显著高于其他各组(P<0.01),对照组的胱氨酸消化率与Ⅴ组无显著差异(P>0.05);随着蛋氨酸添加水平的提高,蓝狐的蛋氨酸消化率相应增高,Ⅵ组显著或极显著高于其他各组(P<0.05或P<0.01),Ⅴ组与对照组差异不显著(P>0.05)。Ⅳ组的总氮排出量显著低于Ⅰ组、Ⅱ组和Ⅲ组(P<0.05),其他各组间无显著差异(P>0.05);Ⅴ组的氮沉积极显著高于其他各组(P<0.01),其他各组间无显著差异(P>0.05);Ⅰ组的净蛋白质利用率显著低于其他各组(P<0.05),其他各组间无显著差异(P>0.05)。综合本试验的各项测定指标,在蛋白质水平为30%的低蛋白质饲粮中添加0.8%的蛋氨酸即饲粮中蛋氨酸水平为1.14%时能够满足育成期蓝狐对蛋氨酸的需要量,此时蓝狐的生长性能、蛋白质消化率和氮沉积较为理想。

This experiment was conducted to study the effects of methane supplementation in low protein diets on growth performance, nutrient digestion and metabolism of growing blue foxes. One hundred and five health male blue foxes at the age of 9 weeks with an average body weight of (2.21±0.60) kg were randomly assigned into 7 groups with 15 replicates per group and 1 fox per replicate. The blue foxes in 6 experimental groups were fed the 30% protein level basal diet (low protein diet) supplemented with 0 (group Ⅰ), 0.2% (group Ⅱ), 0.4% (group Ⅲ), 0.6% (group Ⅳ), 0.8% (group Ⅴ) and 1.0%( group Ⅵ) methine, respectively. The blue foxes in control group were fed the 32% protein level diet (suitable protein diet). The pre-test lasted for 7 days and the trial lasted for 45 days. The results showed as follows: the final body weight (body weight of the 45th day) in the groups Ⅴ and Ⅵ was significantly higher than that in the other experimental groups (P<0.01), but was not significantly different compared with the control group (P>0.05); at the 16th to 30th day, the average daily gain in the groups Ⅳ, Ⅴ and Ⅵ was significantly higher than that in the group Ⅰ (P<0.05), but was not significantly different compared with the control group (P>0.05); at the 31st to 45th day, the average daily gain in the groups Ⅴ and Ⅵ was significantly higher than that in the other experimental groups (P<0.01), and that in the group Ⅴ was also significantly higher than that in the group Ⅵ and control group (P<0.05). The dry matter output in the groups Ⅴ and Ⅵ was significantly lower than that in the other experimental groups (P<0.01), but was not significantly different compared with the control group (P>0.05); the dry matter digestibility in the group Ⅴ was significantly higher than that in the groups Ⅰ, Ⅲ and Ⅳ (P<0.05), but was not significantly different compared with the control group (P>0.05); the protein digestibility in the groups Ⅴ and Ⅳ was significantly higher than that in the groups Ⅰ, Ⅱ and Ⅲ (P<0.05), but was not significantly different compared with the control group (P>0.05); the fat digestibility in the group Ⅰ was significantly lower than that in the other groups (P<0.05), but no significant difference was found among the other groups (P>0.05). The cystine output in the groups Ⅴ and Ⅵ was significantly higher than that in the groups Ⅰ, Ⅱ and control group (P<0.01); the cystine digestibility in the group Ⅵ was significantly higher than that in the other groups (P<0.01), but no significant difference was found between control group and group Ⅴ (P>0.05); the methine digestibility was increased with the methine supplemental level increasing, and that in the group Ⅵ was significantly higher than that in the other groups (P<0.05 or P<0.01), but no significant difference was found between control group and group Ⅴ (P>0.05). Total nitrogen output in the group Ⅳ was significantly lower than that in the groups Ⅰ, Ⅱ and Ⅲ (P<0.05), but no significant difference was found among the other groups (P>0.05); the nitrogen deposition in the group Ⅴ was significantly higher than that in the other groups (P<0.01), but no significant difference was found among the other groups (P>0.05); the net protein utilization in the group Ⅴ was significantly higher than that in the other groups (P<0.05), but no significant difference was found among the other groups (P>0.05). In conclusion, considering all indices of this experiment, when 0.8% methane is supplemented in the low protein diet with 32% protein level, that is, when the dietary methane level is 1.14%, growing blue foxes' methane requirement can be met. In this case, the blue foxes have the optimum growth performance, protein digestibility and nitrogen deposition.