Monitoring of Enzymatic Activity in the Gastrointestinal Tract of Black Sea Salmon (Salmo labrax Pallas, 1814)

Abstract

In this study, it was aimed to determine the activity of digestive enzymes at different time intervals after-feeding throughout the gastrointestinal tract of Black Sea salmon (Salmo labrax). The study was conducted at freshwater recirculating aquaculture systems (RAS). The fish were fed by hand up to satiation for 60 days with diets containing 46.25% protein and 14.90% lipid. The fish gastrointestinal tract including stomach, anterior (with pyloric caeca), middle and posterior sections were taken together at 45th minute, 3rd, 6th, 12th, 24th, 48th, 72nd, and 96th hours post-feeding. The tissues were were stored at -80°C until analyzed. In terms of digestive enzyme activity, at the end of the study, anterior and middle intestine sections had the highest level at 3rd-hour post-feeding. Similarly, pepsin, trypsin, and lipase in the stomach had the highest activity at 3rd-hour post-feeding. However, amylase in the stomach was the highest level at 45th minute and 3rd-hour post-feeding. At 3rd-hours post-feeding, the pepsin in the stomach, the trypsin, and lipase in the anterior section, and the amylase in the middle intestine had the highest levels. Moreover, the correlations between these enzymes were strong in the positive direction. Also, the difference in pepsin, trypsin, amylase, and lipase levels in the samples dissected at different time intervals after feeding was statistically significant. Our results revealed that stomach, anterior, middle, and posterior sections in the gastrointestinal tract of Black Sea salmon had enzyme activity in the different levels, and enzyme activity of these sections changed depending on time post-feeding.