Effects Of Cyclical Starvation And Refeeding On Feeding, Growth Performance And The Intestinal Immune Function In Juvenile Southern Catfish(Silurus Meridionalis)

The purpose of this study investigating the effects of the cyclical starvation and refeeding on growth performance and the intestinalimmune function of juvenile southern catfish(Silurus meridionalis) is to know the characteristics, discipline and physiological mechanisms in the process of compensatory growth andprovide guidance and theoretical basis to discuss the feeding regime, improve the feed efficiency, reduce the production costs and disease control. The study included three parts. A 80-day-multi-cycle experiment was carried out to study the effects of the cyclical starvation and refeeding on growth performance, feed conversion, digestive enzyme activities and intestinal immune function of juvenile southern catfish with initial weight of 22.53±0.08g. Juvenile southern catfish were assigned one of three groups, namely the SOFO(control group,feeding every other day), S10F10(starvation 10d, feeding 10d), S20F20(starvation 20d, feeding 20 d).Part Ⅰ:The effects of the cyclical starvation and refeeding on compensatory growth of juvenile southern catfish.The results showed that the weight of southern catfish was increasing with the development of time. By the end of the experiment, body length and weights of S10OF10, S20F20 were lower than SOFO, and they had significant difference from that of the control group(P<0.05). The research not significantly affected fatness and hepatosomatic index. Specific growth rate of S10F10, S20F20 group in stages of refeeding were higher than that of SOFO in corresponding period. The feed conversion ratio of S10F10 and S20F20 group were higher than SO and had a significant difference(P<0.05).This part of the study showed that S10OF10, S20F20 group of southern catfish generated partial compensation growth through improving feed conversion ratio, so it can save labor costs and is worth a trial in production.Part Ⅱ:It was carried out to study the effects of the cyclical starvation and refeeding on the digestive enzymes of juvenile southern catfish. The results showed that by the end of the experiment trypsin activity and intestinal amylase activity of S10F10 and S20F20 group were significantly reduced compared with the control group(P<0.05), but pepsin activity of S10F10 and S20F20 was the same as that of SOFO. Pancreatic amylase activity of S20F20 group by the end of the experiment was significantly reduced compared with the control group (P<0.05). The intestinal lipase activity of S10F10 and S20F20 group was the same as that of SOFO by the end of the experiment. By the end of the experiment the pancreatic lipase activity of S10F10 and S20F20 group was significantly higher than the control group(p<0.05).This part of the study showed that S10F10 and S20F20 cyclical starvation and refeeding on digestive enzyme activity of juvenile southern catfish had a great impact, resulting in decreasing most digestive enzyme activity and metabolic capacity.Part Ⅲ:It was carried out to study the effects of the cyclical starvation and refeeding on the intestinal immune function of juvenile southern catfish.The results showed that the mucous cells in foregut of S20F20 were significantly less than the control group. The mucous cells in midgut of S10OF10, S20F20 group by the end of the experiment was significantly reduced compared with the control group (P<0.05). The mucous cells in hindgut of S10F10 and S20F20 by the end of the experiment was significantly reduced compared with the control group (P<0.05).The results showed that the intestinal intraepithelial lymphocytes in foregut of S10F10 were significantly less than the control group by the end of the experiment. The intestinal intraepithelial lymphocytes in midgut of S10F10 and S20F20 group were the same as that of SOFO by the end of the experiment. The intestinal intraepithelial lymphocytes in hindgut of S10F10 and S20F20 group were the same as that of SOFO by the end of the experiment.The results showed that PCNA positive cells were distributed in stomach body, foregut, midgut and hindgut, but PCNA positive cells existed only in S20F20 group for stomach body. The PCNA positive cells in foregut of S10F10 group showed a tendency to decrease after the first enhancement with the development of time, but by the end of the experiment were the same as S10F10. The PCNA positive cells in foregut of S20F20 group were increasing with the development of time and by the end of the experiment were significantly increased compared with the control group (P< 0.05). The PCNA positive cells in midgut of S10OF10 group showed a tendency to decrease after the first enhancement with the development of time and that in midgut of S20F20 group also showed decrease after the first enhancement, but by the end of the experiment the PCNA positive cells were significantly increased compared with the control group (P<0.05). The PCNA positive cells in hindgut of S10F10 group showed a tendency to increase after the first enhancement and the second reduction with the development of time and that in hindgut of S20F20 group were increasing, and by the end of the experiment the PCNA positive cells were the same as the control group.This part of the study showed that S10F10 and S20F20 cyclical starvation and refeeding can make the PCNA positive cells in stomach body and intestinal canal of southern catfish have different degrees of increase, thus speed up the growth and peoliferation and promote growth performance of southern catfish, but wakened the intestinal immune function of juvenile southern catfish.Conclusion:S10OF10 and S20F20 group of southern catfish generated partial compensation growth through improving feed conversion ratio, so it can save labor costs and is worth a trial in production. S10F10 and S20F20 cyclical starvation and refeeding decreased digestive enzyme activity of juvenile southern catfish. S10F10 and S20F20 cyclical starvation and refeeding can speed up the growth and peoliferation, promote growth performance of southern catfish, but wakened the intestinal immune function of juvenile southerncatfish.