本试验旨在研究饲粮添加不同水平的β-胡萝卜素对肉牛生产性能、抗氧化功能、血液生理指标和肉品质的影响。选用体况良好、平均体重为（381.00±26.01） kg的西门塔尔杂交阉牛120头，随机分为4组，每组30头，对照组饲喂基础饲粮，试验组饲喂在基础饲粮中分别添加600、1 200和1 800 mg/d β-胡萝卜素的试验饲粮。预试期10 d，正试期90 d。结果表明：1）饲粮添加不同水平的β-胡萝卜素对末重、平均日增重和干物质采食量的影响均不显著（P>0.05）。2）与对照组相比，1 200 mg/d β-胡萝卜素试验组显著提高了血清谷胱甘肽（GSH）含量和总超氧化物歧化酶（T-SOD）活性（P<0.05），而血清丙二醛（MDA）含量则显著降低（P<0.05）；1 800 mg/d β-胡萝卜素试验组显著提高了血清总抗氧化能力（T-AOC）（P<0.05）；随着β-胡萝卜素添加水平的升高，血清T-AOC、GSH含量、T-SOD活性和MDA含量均呈显著的线性和二次改变（P<0.05）。3）与对照组相比，600 mg/d β-胡萝卜素试验组显著降低了血液中间细胞（MID）计数和百分比（P<0.05）；1 800 mg/d β-胡萝卜素试验组血液中性粒细胞（GRAN）百分比显著升高（P<0.05）；随着饲粮β-胡萝卜素添加水平的提高，血液MID计数和百分比呈显著的线性和二次变化（P<0.05），血液GRAN百分比以及白细胞（WBC）和淋巴细胞（LYM）计数均呈显著的线性变化（P<0.05）。4）与对照组相比，1 200 mg/d β-胡萝卜素试验组显著降低了肉色黄度（P<0.05）；随饲粮β-胡萝卜素添加水平的提高，肉色亮度有线性降低的趋势（P=0.079）；不同β-胡萝卜素添加水平对肉中粗蛋白质、粗脂肪、水分、粗灰分含量以及肉色亮度和红度影响均不显著（P>0.05）。总之，肉牛饲粮添加β-胡萝卜素能够显著影响抗氧化功能、血液生理指标和肉品质，本试验条件下，最佳添加水平为1 200 mg/d。

This experiment was conducted to investigate the effects of dietary supplementation of different levels of β-carotene on performance, antioxidant function, blood physiological indices and meat quality of beef cattle. One hundred and twenty healthy Simmental crossbred bullocks with similar weight of (381.00±26.01) kg were randomly divided into four groups with 30 bullocks in each group. Beef cattle in control group were fed a basal diet, and those in experimental groups were fed the basal diet supplemented with 600, 1 200 and 1 800 mg/d β-carotene, respectively, during 10 days of pre-experiment and 90 days of formal experiment. The results showed as follows: 1) no significant differences in final weight, average daily gain and dry matter intake were found in beef cattle received different dietary supplemental levels of β-carotene (P>0.05). 2) Compared with control group, serum glutathione (GSH) content and total superoxide dismutase (T-SOD) activity in 1 200 mg/d β-carotene experimental group were significantly increased (P<0.05), however, serum malondialdehyde (MDA) content was significantly decreased (P<0.05); serum total antioxidant capacity (T-AOC) in 1 800 mg/d β-carotene experimental group was significantly increased (P<0.05). Significant linear and quadratic changes were found in serum T-AOC, GSH content, T-SOD activity and MDA content with the increase of dietary β-carotene supplemental level (P<0.05). 3) Compared with control group, blood middle cell (MID) count and percentage in 600 mg/d β-carotene experimental group were significantly decreased (P<0.05), while blood neutrophile granulocyte (GRAN) percentage was significantly increased in 1 800 mg/d β-carotene experimental group (P<0.05); with the increase of dietary β-carotene supplemental level, significant linear and quadratic changes were found in blood MID count and percentage (P<0.05), and significant linear changes were found in blood GRAN percentage, white blood cell (WBC) count and lymphocyte (LYM) count (P<0.05). 4) Compared with control group, b^* value of meat colour in 1 200 mg/d β-carotene experimental group was significantly decreased (P<0.05); with the increase of dietary β-carotene supplemental level, L^* value of meat colour tended to be linearly decreased (P=0.079); no significant differences were found in crude protein, ether extract, moisture and ash contents in beef and meat color in beef cattle received different dietary supplemental levels of β-carotene (P>0.05). In conclusion, dietary supplementation of β-carotene can significantly affect antioxidant function, blood physiological indices and meat quality of beef cattle, and the optimal supplemental level is 1 200 mg/d under conditions in the present study.