摘要
Abstract
This study aimed to investigate the effects of dietary supplementation with different doses and forms of iodine on growth performance,immune organ indices,thyroid index,serum thyroid hormone levels and thyroid tissue morphology of broilers.A total of 640 one-day-old male Ross 308 broilers were randomly alloca-ted into 8 groups,each with 8 replicates of 10 birds per replicate.A 2×4 factorial design was employed,con-sisting of two forms of iodine(coated calcium iodate and uncoated calcium iodate)and four doses of iodine(0.5,1.0,1.5 and 2.0 mg/kg),resulting in a total of 8 experimental diets.The adaptation period lasted for 7 days,and the formal experiment lasted for 42 days.The results showed as follows:1)dietary supplementation with different doses of iodine significantly affected the average daily gain(ADG)of broilers from 8 to 28 days of age(P<0.05).The ADG of broilers in the 2.0 mg/kg group was significantly higher than that in the 0.5 and 1.0 mg/kg groups(P<0.05),but showed no significant difference compared with the 1.5 mg/kg group(P>0.05).Dietary supplementation with different doses of iodine also significantly affected the thymus index,thyroid index,and serum thyroid hormone levels,including triiodothyronine(T3),thyroxine(T4)and thy-roid-stimulating hormone(TSH)(P<0.05).The 1.5 mg/kg level exhibited the most pronounced effects in in-creasing thymus index and serum T3 and T4 levels.Regarding iodine form,coated calcium iodate significantly increased the thymus index,thyroid index and serum T4 level compared with uncoated calcium iodate(P<0.05).However,histological observation revealed that when the doses of iodine reached 1.0 mg/kg or higher,thyroid follicle volume increased,and cell arrangement irregularity appeared at 1.5 and 2.0 mg/kg.In conclu-sion,under the conditions of this experiment,dietary supplementation with 1.5 mg/kg coated calcium iodate can achieve the optimal balance among promoting immune organ development,optimizing thyroid function and maintaining tissue health in broilers.关键词
碘酸钙/包被碘酸钙/肉鸡/免疫器官指数/甲状腺功能Key words
calcium iodate/coated calcium iodate/broilers/immune organ indexes/thyroid function分类
农业科技
