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

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