Patterns of gastric evacuation and digesta characteristics in the gastrointestinal tract of channel catfish(Ictalurus punctatus) when fed plant protein based diet

The present experiment was conducted to investigate gastric evacuation rates, change of digesta moisture content, pH values and digestive enzyme specific activity along the gastrointestinal tract of channel catfishbody weight(115.55±7.54)gfed plant protein based diet.Three kinds of models used to fit the gastric evacuation were compared.The results showed that:all of these three kinds of models could fit the experimental data quite well, and the square root model was the best, followed by the exponential model and the linear model.The asymptotic level of 50% and 98% gastrointestinal evacuation calculated by the square root model(dry weight basis)apparently reached at 12.8 h and 36 h, respectively.Digesta moisture in the stomach showed a slow increasing trend, the upper intestine and middle intestine showed an increasing trend after the fall, while no changes were found in the lower intestine.The pH values in each part of the gastrointestinal tract decreased significantly within 3 h after feeding(P<0.05), no remarkable changes were found(P>0.05)from 3 to 30 h after feeding, while a noteworthy increasing level, recovering or drawing near the initial level was observed in intestine, within 30-36 h after feeding(P<0.05).The digestive enzyme activity had a significant increase within 3 h(P<0.05)and kept at a stable level within 3-30 h, while had a significant decrease(P<0.05)30 h after feeding.The digestive enzyme specific activity varied in different gastrointestinal sections, and ranged as upper intestine>middle intestine>lower intestine>stomach.In summary:In this study the digesta moisture, pH value and digestive enzyme along the gastrointestinal tract of channel catfish showed a regular change after feeding, and gastric evacuation pattern was affected by the interaction of these factors.