中文摘要：

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、1200和1800 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，1200 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）；1800 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）；1800 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，1200 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，?

英文摘要：

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 ＆lt;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 percenta