| 120 tilapias (average initial weight 75.0±5.0g, 2 months old) were randomly divided into four groups, and they were sacrificed on the 42 days. Control group was fed with basal diets,and the tested diets were that the basal diets added different levels of cysteamine (300mg·kg-1, 600mg·kg-1 and 900mg·kg-1 respectively). The study is aimed at investigating the effects of cysteamine on the structure of intestinal mucous and non-specific immunity.(1) The effects of cysteamine on the structure of intestinal mucous were studied by observing the morphic changes of intestinal villus of the tilapia using HE staining. The results showed that the structure of intestinal mucous was in integrity, and the arrangement of intestinal villus was regular in the tested groups. The length of intestinal villus in the tested groups were much longer than the control group in fore-gut and mid-gut, the heights of the hind-gut villus were shortened in varying degrees; The changes of villus width were not obvious in the experiment; The submucous muscle layer depths increased significantly in mid-gut and hind-gut (P<0 .01), the difference of the submucous muscle layer depths was significant between the 900mg·kg-1 tested group and the control group (P<0.01).(2) The distribution and quantitative changes of goblet cell were observed by AB-PAS staining in fore-gut, mid-gut and hind-gut. The main objective is to find out the quantitative changes of goblet cell at different levels of cysteamine. The results indicated that the difference of quantities of goblet cell was not significant among the groups in fore-gut (p>0.05). The quantities of goblet cell had the trend of increasing in mid-gut and hind-gut, the difference of the goblet cell's quantitywas significant between 600mg·kg-1, 900mg·kg-1 tested groups and the control group (p<0.01).(3) The distribution and quantitative changes of mast cell were observed by Alcian Blue andSafranine O staining in fore-gut, mid-gut and hind-gut. The main objective is to find out the quantitative changes of mast cell at different levels of cysteamine. The results indicated that the difference of quantities of mast cell was significant between the control group and the tested groups in fore-gut and hind-gut (p<0.01), it was not significant among the tested groups (p>0.05); The difference of the mast cell's quantity was not significant in mid-gut among all the groups (p>0.05).(4) The distribution and quantitative changes of intestinal intraepithelial lymphocytes (iIEL) and acidα-naphthyl acetate esterase (ANAE) positive cells by HE and ANAE staining respectively in the intestinal tract in tilapia. The results showed that the quantities of iIEL and ANAE positive cells increased significantly in fore-gut and hind-gut (p<0.01), the difference of them was not significant among the tested groups (p>0.05); The difference of the quantities of iIEL and ANAE positive cells was not significant in mid-gut (p>0.05).(5) In order to investigate the effect on non-specific immunity at different levels of cysteamine, the contents of the lysozyme,catalase and superoxide dismutase were detected in the serum of the tilapia by the heart puncture for collecting blood at 14th, 28th and 42th day. The results indicated that the lysozyme activity,catalase activity and superoxide dismutase activity can be improved in some degree by adding cysteamine in the diet. During the whole experiment, the lysozyme activity increased firstly and then decreased, the lysozyme activity was the highest at 28th day; catalase activity was decreased firstly and then increased, its activity was the lowest at 28th day; The changes range of superoxide dismutase activity were not very obvious.Conclusion: This study indicated that cysteamine can improve the morphological structure of intestinal epithelial cells and the length of villus length, width of villus and submucous muscle layer depth. To some extent, it also can increase the quantity of globle cell , iIEL, mast cell and ANAE positive cell, thus improve the intestinal barrier and immune function. Furthermore, the lysozyme activity, catalase activity and superoxide dismutase activity can be improved in some degree by adding cysteamine in the diet. It could improve the ability of the non-specific immunity of tilapia. |
PDF Full Text Request