Effects of Dietary Protein Source on the Composition of Small Intestinal Fluid of Layer-type Cockerels

This study was conducted to investigate the effects of dietary protein source on the composition of small intestinal fluid in layer-type cockerels,which may provide biological basis for simulating small intestinal fluid in feedstuff evaluation using in vitro digestion approach.A 2×2 factorial completely randomized design was adopted.Twenty-four duodenal cannulated and 24 jejunal cannulated Hyline brown layer-type cockerels with similar weight were selected,and the cockerels of each cannulation type were divided into 2 groups with 4 replicates per group and 3 cokerels per replicate.Duodenal or jejunal digesta samples were collected for 1 h every 4 h from 09:30 to 18:30 on day 31,33,and 35 of the experiment.The intestinal fluid was made by centrifuging digesta samples at 4 ℃.The results showed that there were higher trypsin activity and Cl-concentration but lower K+ concentration in jejunal fluid,and higher lipase activity but lower Mg2+ concentration in duodenal fluid of cockerel fed corn-soybean meal diet than those of birds fed corn-soybean-cottonseed meal diet (P0.05).The composition of the intestinal fluid from different position of the small intestine showed that the amylase and trypsin activities,Na+ and Mg2+ concentrations,and pH were lower,but lipase activity,K+ and Cl-concentrations were higher in duodenal fluid than those in jejunal fluid (P0.05).There were lower amylase and trypsin activities,but higher lipase activity in duodenal fluid than those in jejunal fluid (P0.05).In conclusion,there were significant effects of dietary crude protein source on the digestive enzymes and ion concentrations in intestinal fluid and significant differences in the composition of intestinal fluid from different positions of the small intestine in layer-type cockerels.