APPARENT DIGESTIBILITY COEFFICIENTS OF SEVERAL FEED INGREDIENTS AND THEIR EFFECT ON DIGESTIVE ENZYME ACTIVITIES OF JUVENILE YELLOW CATFISH (PELTEOBAGRUS FULVIDRACO)

To improve the precision of feed formulation, this study investigated effects of soybean meal, fermented soybean meal, rapeseed meal and fermented rapeseed meal on apparent dry matter, protein, energy and amino acids digestibility coefficients using juvenile yellow catfish (Pelteobagrus fulvidraco). The activities of trypsin, chymotrypsin and α-amylase in the stomach, fore-intestine and post-intestine and blood indexes of glutamate transaminase, glutamate transaminase, total protein and alkaline phosphatase were determined. The results indicated that the apparent dry matter digestibility coefficients was significantly different in each treatment (P<0.05), and the utilization rates from high to low were soybean meal, fermented soybean meal, rapeseed meal and fermented rapeseed meal. The lowest apparent protein digestibility was the fermented rapeseed meal group (P<0.05). There was no significant difference in apparent energy digestibility in all 4 treatments (P>0.05). Apparent methionine and histidine digestibility of 4 groups were below 83% without significant difference among groups (P>0.05). The apparent digestibility of other amino acids was significantly different between 85% and 98% with the lowest one in fermented rapeseed meal group (P<0.05). The activities of trypsin of yellow catfish were significantly higher in rapeseed meal treatment than other treatments (P<0.05). The distribution of trypsin activity from high to low was fore-intestine, post-intestine, and stomach. The activities of chymotrypsin were decrescent gradually from stomach to fore-intestine, lowest in post-intestine (P<0.05). The activities of amylase were decrescent gradually from fore-intestine to stomach, min-intestine (P<0.05). The serum glutamic oxalacetic transaminase was significantly higher in soybean meal group than other three treatments (P<0.05) with lower level in groups of rapeseed meal and fermented rapeseed meal. No difference was found in serum glutamic pyruvic transaminase, total protein and alkaline phosphatase in yellow catfish among 4 groups (P>0.05). In conclusion, soybean meal, fermented soybean meal, rapeseed meal and fermented rapeseed meal could be used as high-quality protein sources for yellow catfish.