Abstract: This experiment was conducted to investigate the effects of zinc-montmorillonite (Zn-MMT)on the production performance, slaughter performance, immunologic function and intestinal morphology of broilers. A total of 288 1-day-old male Cob broiler were randomly assigned to 6 groups with 6 replicates per group and 8 birds per replicate. The birds were fed a corn-soybean meal basal diet or one of the four Zn-MMT diets or 40 mg·kg^-1 ZnSO₄ diets, which were the basal diet supplemented with 20, 40, 60，80 mg·kg^-1Zn-MMT(zinc content measurement). The broilers were provided the diets in ad libitum basis.Intestinal tract and spleen were collected on 42 days, and the expression of IL-2, TNF-α, IgG, IgA genes, intestinal villus height and crypts depth were measured. The results showed as follows: 1) Compared with CK group and ZnSO₄ group, Zn-MMT had no significant effect on average daily feed intake (ADFI) of broiler chickens (P>0.05).However, 80 mg·kg^-1 Zn-MMT significantly reduced the average daily gain (ADG) of chicks aged 1-21, 22-42 and 1-42 days (P<0.05), and 40 mg·kg^-1Zn-MMT significantly reduced the feed to gain ratio (F/G) of chicks aged 1-42 days (P<0.05).2) Compared with CK group, ZnSO₄ and 60 mg·kg^-1 Zn-MMT significantly increased the bursa index at 21 days of age (P<0.05), and 60 mg·kg^-1 Zn-MMT significantly increased the bursa index at 42 days of age (P<0.05). At the same time, ZnSO₄, 20 and 40 mg·kg^-1 Zn-MMT significantly increased the expression level of IgG in spleen at 42 days old (P<0.05). Meanwhile, ZnSO₄ group significantly increased the expression level of IgA in the spleen (P<0.05).Compared with CK group and ZnSO₄ group, 20 mg·kg^-1 Zn-MMT significantly improved TNF-α gene expression in spleen. The expression of IL-2 in spleen was significantly increased in 40, 60 and 80 mg·kg^-1 Zn-MMT groups (P<0.05).3) compared with CK, Zn-MMT had no significant effect on the slaughter performance of broilers (P>0.05).4) Compared with CK and ZnSO₄ groups, 40 mg·kg^-1 Zn-MMT significantly increased villus height(VH) and villi height to crypt depth ratio(V/C) of the duodenum and jejunum (P<0.05), and significantly reduced the crypt depth (CD)of the duodenum (P<0.05), but had no significant effect on the ileal CD of ileal (P>0.05). Meanwhile，compared with CK group, 40 mg·kg^-1 Zn-MMT significantly increased the ileal VH and V/C (P<0.05), but had no significant difference with ZnSO₄ group (P>0.05). At the same time，ZnSO₄ had no significant effect on VH ,V/C and CD of duodenum, jejunum, VH and CD of ileum of broilers (P>0.05), but could significantly improve the V/C of ileum (P<0.05). It is concluded that dietary supplementation with Zn-MMT can significantly improve feed conversion rate, enhance body immunity, and promote the development of intestinal villi.

Key words: zinc-montmorillonite, broiler, growth performance, intestinal development, immunologic function