Abstract: 【Objective】 To study the effects of wheat particle size on growth performance,intestinal morphology,digesta enzyme activities and serum biochemical indices of 817 broilers aged 1-20 days.【Method】 A total of 360 1-day-old 817 broilers (male) were randomly divided into 3 groups with 6 replicates per group and 20 chickens per replicate according to the principle of no difference in body weight.The broilers in control group were fed corn-soybean meal diet,and in two experimental groups (1.5 and 2.5 mm groups) were fed diets supplemented with wheat and non-starch polysaccharide enzyme,and the wheat supplemental amount was 25%,and were crushed by 1.5 and 2.5 mm screen size respectively.The trial lasted for 20 d. At 20 days of age,the growth performance of broilers was measured,intestinal tissues and contents,pancreatic tissues and blood of broilers were collected,intestinal morphology,digestive enzyme activity and serum biochemical indexes were determined.【Result】 Compared with the control group,①There were no significant differences in growth performance of broilers in 1.5 and 2.5 mm groups (P＞0.05),but the final body weight and average daily gain of broilers in 1.5 mm group were significantly higher than those in 2.5 mm group (P＜0.05).②The intestinal morphology of broilers in two experimental groups was significantly improved (P＜0.05),and the improvement effect in 1.5 mm group was better than that in 2.5 mm group. ③The activities of duodenal α-amylase,lipase and jejunal trypsin in 1.5 mm group were significantly increased (P＜0.05),the activities of duodenal α-amylase and jejunal trypsin in 2.5 mm group were significantly increased (P＜0.05),and the activities of duodenal lipase were significantly decreased (P＜0.05).The jejunal trypsin activity in 1.5 mm group was significantly higher than that in 2.5 mm group (P＜0.05).④The serum total cholesterol content of broilers in 1.5 mm group was significantly decreased (P＜0.05),and the activities of alanine transaminase (ALT) and aspartate transaminase (AST) in 2.5 mm group were significantly increased (P＜0.05);Serum total cholesterol content,alanine transaminase and aspartate transaminase activities in 1.5 mm group were significantly lower than those in 2.5 mm group (P＜0.05).【Conclusion】 Under the conditions of this experiment,replacing corn with different particle size of wheat (25％ replacement) had no adverse effect on 817 broilers aged 1-20 days.When the particle size of wheat was 1.5 mm,the growth performance,intestinal morphology, digestive enzyme activities and serum biochemical indexes of broilers were the best.

Key words: wheat; particle size; 817 broilers; growth performance; intestinal morphology