Effects of Azomite on Growth,Intestinal Structure and Non-specific Immunity of Tilapia(Oreochromis niloticus×O.aureus)

The experiment was conducted to investigate the effects of adding azomite in diet on growth,intestinal structure and serum non-specific immune index of tilapia(Oreochromis niloticus×O.aureus).Two hundred and forty tilapia with initial body weight of(20.04±0.13) g were randomly divided into 4 groups with 3 replicates of 20 fish.Diets containing 0 (control),0.25%,0.50%and 0.75%azomite were fed to 4 groups for 30 days,then a digestive trial was conducted with supplemental 0.50%Cr_2O_3 in the 4 diets.The results showed as follows:the weight gain rate was increased significantly and FCR was decreased significantly by adding 0.25%～0.75%azomite compared with control group(P0.05).There was no significant difference in the content of crude protein,crude fat,crude ash and moisture of muscle among the 4 groups(P0.05).The height,width and density of intestinal villi,the number of goblet cells,protease activities of intestine and stomach, crude protein digestibility,dry matter digestibility and the number of Lactobacillus of intestine were significantly increased by adding 0.25%～0.50%azomite compared with control group(P0.05).In the respect of non-specific immunity, fish fed with diet supplemented with 0.25%azomite had higher activities of superoxide dismutase and lysozyme than those in control group(P0.05).It was concluded that 0.25%～0.50%of azomite in diet could improve growth performance and intestinal structure,and increase nutrients digestibility and serum non-specific immune function,and the optimum level was 0.25%.