Abstract: The purpose of this experiment was to investigate the effects of different dietary iodine levels on growth performance，immune organ index，blood T3，T4 content and T3/T4 ratio of yellow ? feathered broilers，in order to explore the appropriate level of iodine for yellow?feathered broilers during 1 to 21 days old. A total of 1440 1?day?old healthy and well?developed fast?growing Lingnan yellow?feathered male broilers were randomly divided into 6 groups with 6 replicates per group and 40 chickens in each replicate. The basal diet was supplemented with different doses of Ca（IO3）2，and the dietary iodine supplemental levels were 0.00，0.20，0.40，0.60，0.80 and 1.00 mg/kg， respectively. The results showed that the level of dietary iodine had no significant effect on daily gain，daily feed intake and ratio of feed to gain of chickens（P>0.05）. Using one?slope broken?line analysis，taking the average daily gain asthe evaluation index，the suitable dietary iodine level of chick was determined to be 0.80 mg/kg. Different dietary iodine levels had no significant effect on immune organ index，blood T3，T4 content and T3/T4 ratio of birds. To sum up，the appropriate iodine level of corn?soybean meal diet for 1?21?day?old yellow?feathered male broilers was 0.80 mg/ kg，that is，the optimum level of dietary iodine was 0.91 mg/kg.

Key words: Yellow ? feathered broilers, Iodine, Requirement, Growth performance, Immune organ index, T3 and T4 concentration

摘要： 该试验旨在通过研究饲粮不同碘添加水平对黄羽肉鸡生长性能、免疫器官指数、血 液T3、T4含量及T3/T4比值的影响，以确定1-21日龄黄羽肉鸡饲粮碘适宜添加水平。试验选取1 日龄健康、发育良好的快速型岭南黄羽肉鸡公雏1 440只，随机分成6个处理组，每个处理组6 个重复，每重复40只。各处理组在基础饲粮上分别添加不同剂量的Ca（IO3）2，使饲粮碘添加 水平分别为0.00、0.20、0.40、0.60、0.80、1.00 mg/kg。结果表明：饲粮碘添加水平对试验鸡平均日 增重、平均日采食量、料重比均无显著影响（P>0.05）。采用单斜率折线分析，以平均日增重为 评价指标，确定饲粮碘适宜添加水平为0.80 mg/kg。饲粮不同碘添加水平对试验鸡免疫器官指 数、血液中T3、T4含量及T3/T4的比值均无显著影响。综上所述，1—21日龄快速型黄羽肉鸡公鸡 玉米-豆粕型饲粮的适宜碘添加水平为0.80 mg/kg，即饲粮碘最适宜水平为0.91 mg/kg。

关键词: 黄羽肉鸡, 碘, 需要量, 生长性能, 免疫器官指数, T3和T4浓度