【Objective】 A 4×2 (Cu×VA) experiment with replicates was designed to investigate the influence of various dietary Cu and vitamin A levels on performance, intestinal wall thickness and villus height, cecal gut flora, growth hormone in serum in broilers of different stage (0-4 and 4-7 weeks). 【Method】 The dietary Cu at 0, 8, 150, 225 mg?kg-1 diet and vitamin A at 1 500, 5 000 IU?kg-1 diet were used. Four hundred and fourty-eight avin broilers of 1 day old were randomly allotted to 8 groups, each of which was replicated four times with fourteen broilers per replicate. 【Result】 The performance from 0-4 weeks in group with 8mg?kg-1 copper was better, but from 4-7 weeks group with 0 copper was better. Dietary copper level (225 mg?kg-1 diet) only decreased the ileac wall thickness at the end of week 4, dietary copper level (150 mg?kg-1) significantly decreased the wall thickness of various parts of small intestine at the end of week 7, high copper levels had no effect on villus height in the whole period. When copper supplemental level was 150 mg?kg-1 diet, the amounts of Lactobaccilus and Bifidobacterium significantly increased, and the amounts of E.coli decreased. When copper level was 225 mg?kg-1, the amounts of E.coli significantly increased, and the amounts of Lactobaccilus and Bifidobacterium decreased, the amounts of Salmonella were the least in group with 8 mg?kg-1, copper. Supplement with 5 000 IU?kg-1 VA decreased the intestinal wall thickness at the early stage and the jejunal wall thickness at the later stage significantly, but increased the villus height of duodenum, increased the amounts of Lactobaccilus and E.coli in the whole period and the amounts of Bifidobacterium and Salmonella at the early stage. The interaction of Cu and VA significantly affected the ileac intestinal wall thickness at the early stage, jejunal intestinal wall thickness at the later stage (P＜0.05), duodenal villus height at the early stage, villlus height of duodenum and ileum at the later stage (P＜0.01), the amounts of Lactobaccilus, Bifidobac- terium, E.coli and Salmonella through the whole period (P＜0.01). The level of dietary copper and VA had no effect on GH in serum (P＞0.05), the concentration at the early stage was higher. 【Conclusion】 Dietary copper level (150 mg?kg-1) and dietary VA level (5 000 IU?kg-1) is beneficial to the absorption of nutritive materials and the balance of gut flora. The interaction between dietary copper and VA existed.
