Rate of ingestion and proteolytic activity in digestive system of juvenile white shrimp, Penaeus vannamei, during continual feeding

摘要

The rate of ingestion of juvenile white shrimp, P. vannamei, using tray feeders was estimated during continual feeding over a 24-h cycle. Proteolytic activity was also evaluated with starved and fed organisms during the daily cycle. Juvenile shrimp,4.4 g, were placed in outdoor 2000-litre polyethylene tanks with sand-layer bottom and 80 organisms per tank. During the 4-day feeding trial, weight gains in fed and starved shrimp were recorded. On the fifth day, shrimp were sampled every 2 h for the study of digestive enzymes. Feed ingestion was calculated by subtracting the uningested and the leached material from the feed provided. Differences (P<0.05) in the ingestion rate were found during the experiment. The greatest ingestion occurred between 20.00 and 22.00 h. The largest feed ingestion coincided with the nocturnal activity of shrimp. Time-series analysis showed a cycle of increased ingestion before midnight and lower ingestion during daylight. Total protease, trypsin and chymotrypsin activity were measured during the last 24 h of the study and included fed and starved organisms. The enzymic pattern was similar for both groups. There was a decrease in protease and trypsin activities before and after 18.00 h, just before the ingestion increased. The study of digestive enzymes provided evidence of a close association between behaviour and regulation of the digestion system physiology. The results contribute toward better feeding regimens and the use of feed management for continual monitoringof ingestion to obtain reliable evaluations for the feed conversion index. Feed management with tray feeders will reduce pollution in extensive ponds by decreasing the uningested food.