Effects of delayed first feeding on the growth,feeding and activities of digestive enzyme of theMyxocyprinus asiaticuslarvae

Abstract

To investigate the effects of different starvation periods on the growth capacity,feeding and activities of digestive enzyme of the Myxocyprinus asiaticus larvae under the condition of w ater temperature( 19 ± 0. 5) ℃,two experiments were performed. The first one was a controlled experiment with one complete starvation group( S) and one normal feeding group( C). The second w as the delayed first feeding experiment along w ith the initial feeding time groups: 0( control group),1,3,5,7,9 and 11 delayed days groups,denoted as D0,D1,D3,D5,D7,D9 and D11. The total experimental period lasted 29 days. Results show ed that:( 1) Since hatching,larvae's first feeding w as on the 7th day,and the yolk w as exhausted on the14th day,w hile PNR( the point of no return) appeared on the 27th day,w ith conspicuous pectoral angle characteristics and significant increase in mortality around the PNR.( 2) After refeeding,compared to the control group,the D1 and D3 groups show ed no significant difference in body w eight,indicating a complete compensation effect.( 3) During the 1th to the 7th day starving process,the trypsin and amylase enzyme activity decreased significantly( P 0. 05),w hile w hen prolonging the starvation time to 9 and 11 days,the lipase and trypsin enzyme activity rose significantly( P 0. 05). After refeeding,w ith starvation time lasting,to the 19th day larvae,the trypsin activity significantly increased and then gradually decreased,but indicated the opposite trend on the amylase activity,to the 29th day larvae,and both of lipase and amylase show ed a significant upw ard trend. To sum up,our results indicated that starvation can cause significant changes of M.asiaticus in the larvae grow th,feeding and digestive enzymes,along w ith different compensatory grow th mechanism after various starvation time periods. After recovering feeding,the digestive enzymes recovery strategy is not consistent for larvae are w ith different starvation time. Totally,larvae are inclined to use the small carbohydrates along w ith starvation time lasting. But the inherent mechanism needs further study.