本试验旨在寻找通过营养调控缓解牦牛僵牛氧化和免疫应激，促进牦牛僵牛生长的方法。按小于同龄同品种牦牛群体平均体重1.5倍标准差的标准选取1周岁青海高原型牦牛僵牛40头和正常牦牛10头，按体重将40头牦牛僵牛随机分为4组，分别为僵牛放牧组、精补组、半胱胺组（补饲精料同时添加80 mg/kg BW半胱胺）、酵母组（补饲精料同时添加0.3%活性干酵母），正常牛设为正常牛放牧组，每组5个重复，每个重复2头牛。预试期15 d，正试期60 d。结果表明：1）与放牧僵牛组相比，精补组、半胱胺组、酵母组可显著提高僵牛体尺指标（P<0.05）。2）精补组血液红细胞计数和血红蛋白含量显著高于僵牛放牧组（P<0.05），血液白细胞计数显著低于僵牛放牧组（P<0.05）。3）在第1天，正常牛放牧组血浆丙二醛（MDA）含量显著低于其他4组（P<0.05），总超氧化物歧化酶（T-SOD）活性、谷胱甘肽过氧化物酶（GSH-Px）含量、总抗氧化能力（T-AOC）抗氧化能力显著高于其他4组（P<0.05）。在第60天，半胱胺组和酵母组僵牛血浆中MDA含量显著低于第1天（P<0.05），且显著低于僵牛放牧组（P<0.05），血浆T-SOD活性、T-AOC显著高于第1天（P<0.05），且显著高于僵牛放牧组（P<0.05）；酵母组血浆GSH-Px含量显著高于第1天（P<0.05），且显著高于僵牛放牧组（P<0.05）。4）在第1天，正常牛放牧组血浆免疫球蛋白A（IgA）、免疫球蛋白G（IgG）含量显著高于其他4个组（P<0.05）。第60天，精补组血浆IgG含量显著高于第1天（P<0.05），且显著高于僵牛放牧组（P<0.05）；半胱胺组血浆IgA含量显著高于第1天（P<0.05），且显著高于僵牛放牧组（P<0.05）；酵母组的血浆IgA和IgG的含量显著高于第1天（P<0.05），且显著高于僵牛放牧组（P<0.05）。结果提示，补饲精料及精料中添加80 mg/kg BW半胱胺或0.3%活性干酵母可提高牦牛僵牛抗氧化和免疫能力，促进僵牛补偿生长，其中补饲精料同时添加0.3%活性干酵母效果最佳。

In order to find methods for relieving oxidative and immune stress, and promote growth of yaks with growth retardation, forty 1-year-old Qinghai high plateau yaks with growth retardation (which was 1.5-fold standard deviations less than the average weight of yak groups with same age and breed) were selected and randomly assigned into 4 groups, which were farming yaks with growth retardation group, concentrate group, cysteamine group (concentrate+80 mg/kg BW cysteamine) and yeast group (concentrate+0.3% active dry yeast); another ten 1-year-old Qinghai high plateau yaks with normal growth performance were selected as farming healthy yaks group. Each group had 5 replicates with 2 yaks per replicate. The pre-trial lasted for 15 d, and the trial lasted for 60 d. The results showed as follows:1) compared with farming yaks with retardation group, body measurements in concentrate group, cysteamine group and yeast group were significantly increased (P<0.05). 2) Compared with farming yaks with retardation group, concentrate group had significantly higher red blood cell count and hemoglobin content, and significantly lower white blood cell count in blood (P<0.05). 3) On day 1, plasma malondialdehyde (MDA) content in farming healthy yaks group were significantly lower than that in the other four groups (P<0.05), and plasma total superoxide dismutase (T-SOD) activity, glutathione peroxidase (GSH-Px) content and the total antioxidant capacity(T-AOC) in farming healthy yaks group were significantly higher than those in the other four groups (P<0.05). On day 60, plasma MDA content in cysteamine group and yeast group was significantly decreased compared with day 1 (P<0.05), and was significantly lower than that farming yaks with retardation group (P<0.05); plasma T-SOD activity and total antioxidant capacity (T-AOC) in cysteamine group and yeast group were significantly increased compared with day 1 (P<0.05), and were significantly higher than those farming yaks with retardation group (P<0.05); plasma GSH-Px content in yeast group was significantly increased compared with day 1 (P<0.05), and was significantly higher than that in farming yaks with retardation group (P<0.05). 4)On day 1, plasma immunoglobulin A (IgA) and immunoglobulin G (IgG) contents in farming healthy yaks group were significantly higher than those in the other four group (P<0.05). On day 60, plasma IgG content in concentrate group was significantly increased compared with day 1 (P<0.05), and was significantly higher than that in farming yaks with retardation group (P<0.05); plasma IgA content in cysteamine group was significantly increased compared with day 1 (P<0.05), and was significantly higher than that in farming yaks with retardation group (P<0.05); plasma IgA and IgG contents in yeast group were significantly increased compared with day 1 (P<0.05), and were significantly higher than that in farming yaks with retardation group (P<0.05). The results indicate that concentrate supplementation and further supplementation of 80 mg/kg BW cysteamine and 0.3% active dry yeast can improve antioxidant capacity and immunity of yaks with growth retardation, and promote compensatory growth; the supplementation of concentrate and 0.3% active dry yeast has the best effects.