中文摘要：

本研究旨在研究烟酸对未去势湘中公牛生长性能、肉品质和血清生化指标的影响。选择1.5岁左右体重[（385.08±15.20） kg]匀称的未去势湘中黑公牛21头,随机分成3组,每组7头,各组分别在基础饲粮中添加0、800、1200 mg/kg烟酸。预试期14 d,正试期120 d。结果表明：烟酸对公牛的平均日增重、日均采食量、饲料转化率、背膘厚、眼肌面积均没有显著影响（P〉0.05）。烟酸对背最长肌的pH、肉色亮度和红度值、剪切力、滴水损失以及水分、粗脂肪和粗蛋白质含量均没有显著影响（ P〉0.05）。1200 mg/kg烟酸显著降低血清总胆固醇和高密度脂蛋白胆固醇（HDL-C）含量（P〈0.05）,800 mg/kg烟酸显著降低血清HDL-C含量（P〈0.05）,烟酸对低密度脂蛋白胆固醇含量没有显著影响（ P〉0.05）。1200 mg/kg烟酸可以提高血清非酯化脂肪酸（ P〈0.05）和葡萄糖含量（ P=0.06）,降低血清尿素氮含量（ P=0.07）。综上,本研究并没有观察到烟酸对未去势湘中公牛生长性能和肉品质等指标有影响,但对血脂指标有一定调节作用,推测可能是未去势公牛的雄性激素的作用覆盖了烟酸的作用。

英文摘要：

The aim of this study was to test the effects of nictinic acid （ NA） on performance, meat quality and serum biochemical parameters of uncastrated Xiangzhong bulls. Twenty-one 1. 5-year-old uncastrated Xiangzhong black bulls with similar body weight [（385.08±15.20） kg] were randomly assigned to three groups with seven individuals in each group. The experimental animals from each group were provided with a basal diet added 0, 800 and 1 200 mg/kg NA, respectively. The pre-experimental period lasted for 14 days, and the experimental period lasted for 120 days. The results showed as follows：NA had no significant effects on average daily gain, average daily feed intake, feed conversion rate, back fat thickness and loin eye area of uncastrated bulls （P〉0.05）. It also had no significant effects on pH, meat color L？ and a？ values, shear force, drip loss and the contents of moister, ether extract and crude protein of longissimus muscle （P〉0.05）. The supplementation of 1 200 mg/kg NA significantly reduced the serum total cholesterol and high density lipoprotein cholesterol （ HDL-C） contents （ P〈0.05） , and that of 800 mg/kg NA significantly reduced serum HDL-C content （ P〈0.05） , but NA had no significant effect on serum low density lipoproten-cholesterol content （ P〉0.05） . The supplementation of 1 200 mg/kg NA could increase serum nonesterified fatty acid （ P〈0.05） and glucose contents （P=0.06）, but could decrease serum urea nitrogen content （P=0.07）. In conclusion, no effects of NA are observed on growth and meat quality of uncastrated bulls, but NA has some regulation effects on blood lipids, which may due to that the effects of androgen in uncastrated bulls covered the effects of NA.