Exploring the in vivo digestion of plant proteins in broiler chickens

Abstract

The use of various protein sources (industry by-products, proteaginous) in poultry diets requires a greater understanding of protein digestion mechanisms. The aim of this study was to characterize the molecular actors required for protein digestion in broilers fed 4 different diets containing soybean meal, rapeseed meal, pea, or corn distiller's dried grain with solubles as the only protein source. The digesta of the digestive tract segments were collected and soluble proteins were analyzed by SDS-PAGE. SDS-PAGE analyses revealed 5 ubiquitous bands in digesta of all digestive tract segments regardless of the diet, whereas 3 bands were diet-specific. The digesta of the jejunum were further submitted to proteomic analysis. Forty-two proteins of chicken origin and 17 plant proteins were identified in digesta samples by mass spectrometry. Fifteen proteins of chicken origin were specific to one diet and 18 were common to all diets. By homology with mammals, these proteins are thought to be involved in protein, lipid, carbohydrate, and nucleic acid metabolism and also in intestinal homeostasis. Some of the 17 plant proteins were found to be not fully digested (soybean meal, rapeseed meal, and pea diets) and others were identified as protease inhibitors (soybean meal and pea diets). This study provides a comprehensive analysis of the physiological proteins involved in the digestion of 4 protein sources used in broiler diets. Such an approach, combined with the analysis of insoluble components of these different protein sources, would contribute to define whether these protein sources could be more largely used in poultry nutrition. It also would allow identifying ways to improve their digestibility in broiler chickens (feed additives such as exogenous proteases or processing to inactivate anti-nutritional factors, for instance).

Blood Parameters, Digestive Organ Size and Intestinal Microflora of Broiler Chicks Fed Sorghum as Partial Substitute of Corn

“…There were no significant dietary treatments effect (P>0.05) on relative digestive organ weight and length of the intestinal tract at 35 d of age (Table 3 Contrary, Fernandes et al (2013) observed that the inclusion of different sorghum particle size (partially ground or whole grain) in the broiler diets significantly increase gizzard and small intestine weight, which could be explained due to a greater development of the intestinal mucosa (Tarachai and Yamauchi, 2000). The pH in the digestive tract segments is very important in protein digestion as it affects the processing of endogenous proteases into their mature form, but also the solubility of the dietary proteins (Recoules et al, 2017). Our results shown that the value of intestinal digesta pH (Table 3) was similar in broilers fed the WS compared with C diet (P>0.05) and as expected, the pH value increased in the different segments of the digestive tract from 5.59 (duodenum) to 6.56 (caecum).…”

Comparative study of protease hydrolysis reaction demonstrating Normalized Peptide Bond Cleavage Frequency and Protease Substrate Broadness Index

“…However, digestion by endogenous protease is incomplete. Recent studies using proteomics approaches have revealed the presence of partially digested proteins from soybean meal (and other legume and cereal feed ingredients) in broiler digesta [2,3]. It is estimated that only about 80% of dietary soybean meal is digested by swine and poultry [4,5] or even less in high fiber, high phytate diets such as those containing industrial by-products [6,7].…”

Digestion dynamics in broilers fed rapeseed meal

“…The interaction of these plant proteins with the enzymes secreted by the digestive tract within each segment and not only the ileum, is also very important to better appreciate the dynamics of protein digestion. The catalog of proteins/enzymes that participate in chicken digestive processes is not yet complete, although some recent proteomic approaches on jejunum 6 and ileum 7 allowed the identification of many other proteins in addition to the well-known pepsin, chymotrypsin, trypsinogens and amylase 8–13 . The activity and function of most of these emerging molecules are still predicted based on homologies with bovine and porcine species, and their secretion by each digestive segment in chicken species have not yet been investigated.…”