本试验旨在研究饲粮2-羟基-4-(甲硫基)丁酸异丙酯(HMBi)添加水平对山羊生长性能、营养物质表观消化率及血清生化指标和激素水平的影响,以确定山羊饲粮中HMBi的最佳添加水平.选择36只2.5月龄左右、平均体重为(13.33 ±1.71)kg的山羊,随机分为4组,每组3个重复,每个重复3只(公阉羊1只,母羊2只),各组山羊分别饲喂HMBi添加水平为0(对照组)、0.05%、0.10%、0.20%(干物质基础)的试验饲粮.预试期10 d,正试期40 d.结果显示:1)0.10%组山羊的平均日增重最高,为158.89 g/d,料重比最低,为4.82,经济效益最佳,且其平均日增重和毛收益均显著高于对照组(P<0.05),0.20%组、0.50%组和对照组的平均日增重分别为141.11、140.56、119.44 g/d.2)干物质、中性洗涤纤维、酸性洗涤纤维和消化能表观消化率各组间均无显著差异(P>0.05).0.10%组的粗蛋白质表观消化率显著高于对照组(P<0.05).3)试验第1天,各组山羊血清尿素氮(UN)、葡萄糖(GLU)、甘油三酯(TG)、总胆固醇(TC)、游离脂肪酸(NEFA)、总氨基酸(TAA)含量及生长激素(GH)与类胰岛素生长因子-Ⅰ(IGF-Ⅰ)水平均无显著差异(P>0.05).试验第31天,0.20%组山羊血清 TG 含量显著高于其他3组(P<0.05);0.20%组山羊血清TC含量显著低于对照组(P<0.05);0.20%组山羊血清NEFA含量极显著高于对照组(P<0.01),显著高于0.05%组(P<0.05);0.05%、0.10%和0.20%组山羊血清TAA含量显著高于对照组(P<0.05);0.05%和0.10%组血清 GH 水平显著高于对照组(P<0.05),0.20%组血清GH水平与对照组相比有增加的趋势(P=0.084);血清IGF-Ⅰ水平各组之间无显著差异(P>0.05).由此说明,饲粮中添加HMBi有利于提高山羊对蛋白质的消化利用,促进山羊生长,且添加水平为0.10%(干物质基础)时经济效益最佳.%This experiment was conducted to investigate the effects of 2-hydroxy-4-(methylthio)butanoic acid isopropyl ester(HMBi)supplementaal level on growth performance,nutrient apparent digestibility,serum bio-chemical indices and hormone levels of goats, aiming to determine the optimal supplemental level of HMBi in diets for goats. Thirty-six goats of about 2.5-month-old with an average body weight of(13.33±1.71)kg were randomly assigned to 4 groups with 3 replicates within each group, and one male goat and two female goats within each replicate. The goats in the 4 groups were fed the experimental diets containing 0(control group), 0.05%,0.10% and 0.20% HMBi on dry matter basis, respectively. The pre-experiment lasted for 10 days, and the formal experiment lasted for 40 days. The results showed as follows:1)the average daily gain of the control group,0.05% group,0.10% group and 0.20% group was 119.44,140.56,158.89 and 141.11 g/d, respectively. The 0.10% group had the greatest average daily gain, the lowest feed/gain of 4.82, and the best economic benefit. The average daily gain and gross returns of the 0.10% group were significantly greater than those of the control group(P<0.05). 2)No significant differences were found in apparent digestibility of dry matter, neutral detergent fiber,acid detergent fiber and digestible energy among groups(P>0.05). The appar-ent digestibility of crude protein of the 0.10% group was significantly higher than that of the control group(P<0.05). 3)There were no significant differences among all groups on the 1st day of the test in terms of the con-tents of urea nitrogen,glucose,triglycerides,total cholesterin,non-esterified fatty acid,total amino acid,and the levels of growth hormone and insulin-like growth factor-1 in serum(P>0.05). On the 31st day of the test, the serum triglycerides content of the 0.20% group was significantly higher than that of the other three groups (P<0.05); the serum total cholesterin content of the 0.20% group was significantly lower than that of the control group(P<0.05); the serum non-esterified fatty acid content of the 0.20% group was significantly higher than that of the control group(P<0.01)and the 0.05% group(P<0.05); the serum total amino acid content of the control group was significantly lower than that of the other groups(P<0.05);the serum growth hormone level of the control group was significantly lower than that of the 0.05% and 0.10% groups(P<0.05);the 0.20% group tended to increase serum growth hormone level compared with the control group(P=0.084); there was no significant difference in serum insulin-like growth factor-Ⅰ level among all groups(P>0.05). It is concluded that dietary supplementation of HMBi can improve the digestive utilization of protein, and then promote the growth of goats. Moreover, supplementation of 0.10% HMBi on the dry matter basis shows the best economic benefits.
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