Releasing Law And Absorption Characteristics Of Peptides From Protein Feeds In Gastrointestinal Tract Of Chickens

The releasing law and absorption characteristics of peptides from protein feeds in gastrointestinal tract of chickens were investigated in this paper from following four aspects.1. The methodology of forcefeed was used to investigate peptides releasing law in gastrointestinal tract and their intact absorption in portal blood in chickens. Peptides releasing characteristics from protein feeds of different qualities in jejunum and their effects on portal peptides were also studied. The portal blood and chyme in different segments of gastrointestinal tract were collected at designated times after forcefeed. The results showed that the highest Peptide-bounded amino acid (PAA) releasing amounts were removed from stomach to duodenum and jejunum with the extension of digestion time; Jejunal PAA releasing amounts from different protein feeds were significantly different. Quality feeds released more PAA than poor feeds; Most of the intact peptides in gastrointestinal chyme were not absorbed into portal blood.2. To investigate the releasing characteristics of low molecular weight oligo-peptides from protein feeds of different qualities, four feeds of Fish meal, soybean meal, cottonseed meal and rapeseed meal were in vitro hydrolyzed using pepsin and trypsin and the hydrolysates were treated using the methodology of ultra-filtration to prepare low molecular weight fractions (<3kDa and <1kDa) . The results showed that feed quality significantly affected the releasing amount and variety of oligo-peptides during in vitro enzymatic hydrolysis. The quality feeds containing more essential amino acids (EAA) released more oligo-peptides than those poor feeds containing less EAA.3. The methodology of duodenal infusion was used to investigate the effects of dipeptide, free amino acids mixture and feed oligo-peptides on intestinal absorptive rate of amino acids and portal peptides in chickens under unanesthetized condition. The infused feed oligo-peptides were prepared using enzymatic hydrolysates of fish meal, soybean meal, cottonseed meal and rapeseed meal with the average molecular weight of <3kDa and <1kDa. Portal blood was collected at designated times after duodenal infusion of a dipeptide of Ala-Gly, a mixture of Ala and Gly (Ala+Gly) and eight feed oligo-peptides. The index of absorptive intensity and absorptive balance were used to estimate the intestinal absorption rate of amino acids. The results suggested that the absorption rate of Ala-Gly were higher than that of its corresponding free amino acid mixture of Ala+Gly; There exited a positive correlation between peptide-bounded amino acid content (PAA/TAA) in infused samples and the intestinal absorption rate of amino acids.4. The methodology of everted sacs was used to investigate the intact absorption of feed oligo-peptides in chickens' small intestine. The everted sacs of lower jejunum and upper ileum were prepared. Eight culture fluids containing feed oligo-peptides were prepared using enzymatic hydrolysates of fish meal, soybean meal, cottonseed meal and rapeseed meal with the average molecular weight of <3kDa and <1kDa. The result showed that most of the intact oligo-peptides in culture fluids were not absorbed by lower jejunum and upper ileum of chickens.