Dietary protein effects on growth performance, carcass traits and expression of selected jejunal peptide and amino acid transporters in broiler chickens

A Corzo,Sc Burgess,Ii Re Loar,Mt Kidd

doi:10.1590/s1516-635x2011000200008

Abstract

The effect of dietary protein on growth, carcass traits and some specific intestinal intestinal peptide and amino acid transporters in broiler chickens was studied. Birds received a common pre-test diet, and were subsequently fed either a standard positive control diet (PC) or a reduced CP diet (RCP) from 21 to 42 d of age. Growth was negatively impacted with feeding of RCP as manifested by an increase in feed consumption and feed conversion ratio. Carcass traits also showed evidence of negative effects of feeding the RCP diet, leading to a reduction in carcass and breast meat yield and an increase in abdominal fat percentage. Blood plasma total protein was reduced when the broilers were fed the RCP diet. Expression of mRNA for one peptide (PepT1) and four AA intestinal transporters (b o,+ AT; CAT2; y + LAT2; EAAT3) was measured from the jejunum. Quantified mRNA for the AA transporters y + LAT2 and EAAT3 showed that they were upregulated in chickens fed the RCP-diet. The transport systems PepT1, b o,+ AT, and CAT2, were not affected by the dietary treatment imposed. The live and processing data validated the in vivo portion of the study and elucidated the negative impact of feeding the RCP diet, while the responses observed with the expression of the various transporters may help provide some insight on the physiological consequences and adaptations that birds endure when provided diets too low in CP for abnormally extended periods of time.

Highlights

The digestive processes that occur during gastric and intestinal digestion in the chicken have been well elucidated (Menzies & Fisk, 1963; Zelikson et al, 1971; Scott et al, 1982)
It can be observed that both treatments resulted in similar (p > 0.05) BW gain values, but it was obvious that this was as a consequence of the birds given the reduced CP diet (RCP)-diet increasing (p ≤ 0.01) their feed consumption patterns
This resulted in a poorer (p ≤ 0.001) feed conversion value by the birds fed the RCP-diet when compared to those fed the positive control diet (PC)-diet

Summary

Introduction

The digestive processes that occur during gastric and intestinal digestion in the chicken have been well elucidated (Menzies & Fisk, 1963; Zelikson et al, 1971; Scott et al, 1982). Denaturation of dietary proteins in feedstuffs is initiated prior to ingestion of proteinrelated foods, and occurs during the high temperatures to which feed ingredients are exposed during the feed manufacturing process (Briggs et al, 1999). In most countries feed is pelleted which exposes it to temperatures ranging from 80 to 90 °C. Tertiary and quaternary structures of protein present in animal and vegetable feed ingredients can be disrupted This denaturation process is almost completed when food reaches the gastrointestinal tract of the bird where a multitude of enzymatic and acidic reactions cleave specific peptide linkages, and other related bonds associated with protein conformation. The result of this degradation process is the release of a number of individual amino acids (AA) and some short peptides

Methods

Results

Conclusion