本试验旨在探究饲粮中添加不同水平酵母细胞壁对断奶羔羊生长性能、免疫能力及胃肠道发育的影响。选取日龄和初始体重相近、生长状况良好的哺乳羔羊48只，随机分为4组，每组3个重复，每个重复4只，各组开食料中酵母细胞壁添加量分别为0（Ⅰ组，作为对照组）、0.25%（Ⅱ组）、0.50%（Ⅲ组）、0.75%（Ⅳ组）。试验期60 d。结果显示：Ⅲ组的平均日增重（ADG）最大、料重比（F/G）最低，其中ADG比Ⅰ组提高了23.6%（P<0.05），F/G比Ⅰ组降低了33.3%（P<0.05）。Ⅲ组血清免疫球蛋白A （IgA）和免疫球蛋白G （IgG）含量较Ⅰ组显著增加（P<0.05）；Ⅲ组和Ⅳ组血清白细胞介素-2（IL-2）、白细胞介素-4（IL-4）、白细胞介素-1β（IL-1β）含量均较Ⅰ组显著增加（P<0.05）；Ⅳ组血清肿瘤坏死因子-α（TNF-α）含量较Ⅰ组和Ⅲ组分别提高了17.9%和24.8%（P<0.05）。Ⅲ组的瘤胃乳头长度分别比Ⅰ组、Ⅱ组和Ⅳ组增加了24.5%、14.7%和24.5%（P<0.05），瘤胃乳头宽度比Ⅰ组增加了26.4%（P<0.05）。Ⅲ组的回肠绒毛高度比Ⅰ组和Ⅱ组分别增加了19.0%、18.2%（P<0.05），回肠肌层厚度比Ⅰ组和Ⅱ组分别增加了32.7%、22.9%（P<0.05）。Ⅳ组的十二指肠绒毛高度比Ⅰ组和Ⅱ组分别增加了46.8%和31.3%（P<0.05）；Ⅲ组的十二指肠隐窝深度比Ⅰ组和Ⅱ组分别增加了29.4%、20.5%（P<0.05），十二指肠肌层厚度比Ⅰ组、Ⅱ组分别增加了76.9%、59.9%（P<0.05）。综上可知，饲粮中添加酵母细胞壁能够增强断奶羔羊的免疫能力，改变其胃肠道形态，提高生长性能。在本试验条件下，断奶羔羊饲粮中酵母细胞壁的添加量以0.50%为宜。

The purpose of this study was to explore the effects of adding different levels of yeast cell wall to the diet on growth performance, immunity and gastrointestinal tract development of weaned lambs. In the experiment, forty-eight lactating lambs with similar age and initial body weight and good growth conditions were selected and randomly divided into 4 groups with 3 replicates per group and 4 lamps per replicate. The amount of yeast cell wall added to each group of diet was 0 (group Ⅰ), 0.25% (group Ⅱ), 0.50% (group Ⅲ) and 0.75% (group Ⅳ), and the test period was 60 days. The results showed that the average daily gain (ADG) was the largest and the feed/gain (F/G) was the lowest in group Ⅲ; the ADG of group Ⅲ was increased by 23.6% (P<0.05), and the F/G was decreased by 33.3% compared with group Ⅰ (P<0.05). The contents of serum immunoglobulin A (IgA) and immunoglobulin G (IgG) of group Ⅲ were significantly increased compared with group Ⅰ (P<0.05); the contents of serum interleukin-2 (IL-2), interleukin-4 (IL-4) and interleukin-1β (IL-1β) of groups Ⅲ and Ⅳ were significantly increased compared with group Ⅰ (P<0.05); the content of serum tumor necrosis factor-α (TNF-α) of group Ⅳ was increased by 17.9% and 24.8% compared with groups Ⅰ and Ⅲ (P<0.05), respectively. The rumen papilla length of group Ⅲ was increased by 24.5%, 14.7% and 24.5% compared with groups Ⅰ, Ⅱ and Ⅳ (P<0.05), respectively, and the rumen papilla width was increased by 24.5% compared with group Ⅰ (P<0.05). The ileal villus height of group Ⅲ was increased by 19.0% and 18.2% (P<0.05), and the ileal muscle thickness was increased by 32.7% and 22.9% compared with groups Ⅰ and Ⅱ (P<0.05), respectively. The duodenal villus height of group Ⅳ was increased by 46.8% and 31.3% compared with groups Ⅰ and Ⅱ (P<0.05), respectively. The duodenal crypt depth of group Ⅲ was increased by 29.4% and 20.5%(P<0.05), and the duodenal muscle thickness was increased by 76.9% and 59.9% compared with groups Ⅰ and Ⅱ (P<0.05), respectively. In conclusion, adding yeast cell wall to the diet can enhance the immunity, change the gastrointestinal tract morphology, and improve the growth performance of weaned lambs. In this experiment condition, the suitable additive amount of yeast cell wall to the diet of weaned lamb should be 0.50%.