Abstract
BackgroundThere is growing interest in carbohydrate and protein nutrition to enhance the efficiency of animal production. Reduced-crude protein diets depress environmental pollution and feeding cost, but the challenge to their adoption is maintaining digestive function and growth performance of birds. The present study was conducted to evaluate the influence of different dietary starch sources and protein levels on intestinal functionality and mucosal amino acid catabolism.MethodsSix dietary treatments, based on maize and soybean meal, were offered to 360 AA+ male chicks from 6 to 35 d post-hatch as a 3 × 2 factorial array. Either waxy rice or amylose was added to a conventional maize-soy diet to provide three sources of starch with different digestion rates and relatively high and low dietary protein levels. Growth performance, parameters of intestinal functionality and concentrations of free amino acid in the portal circulation were determined.ResultsIn the grower phase, starch source influenced (P < 0.02) weight gain as diets containing amylose supported significantly higher weight gains than waxy rice. Significant increase of ileal ATP concentrations and Na+/K+-ATPase activity were found in amylose treatment. Also, amylose decreased BrdU positive cell numbers and down-regulated mRNA expression for CASP-3. GOT activity in the ileum was higher (P < 0.01) in birds offered low protein diets and there was a trend (P = 0.057) for waxy rice as a starch source to increase ileal GOT activities. There was a significant influence on the concentration of seventeen amino acids in the portal circulation with tryptophan the one exception. Waxy rice as a starch source generated 13.6% and 22.4% numerically higher concentrations of non-essential amino acids than maize and amylose, respectively.ConclusionsAmino acid catabolism in the gut mucosa is subject to nutritional regulation. Given that amino acids can be spared from catabolism in the gut mucosa by supplementation of amylose, it follows their post-enteral availability would be improved and intestinal energy would be derived more efficiently from glucose.
Highlights
There is growing interest in carbohydrate and protein nutrition to enhance the efficiency of animal production
The different starch sources consisted of waxy rice, maize grain and amylose and protein levels were adjusted by maize gluten meal inclusions
The outcomes of this study indicate that free amino acid concentrations in the portal circulation can be modified by dietary strategies
Summary
There is growing interest in carbohydrate and protein nutrition to enhance the efficiency of animal production. Reduced-crude protein diets depress environmental pollution and feeding cost, but the challenge to their adoption is maintaining digestive function and growth performance of birds. Reduced-crude protein diets have been shown to depress nitrogen excretion and have the potential to reduce feeding costs but the challenge to their adoption is maintaining digestive function and growth performance of birds [1]. Different carbohydrate (starch) sources in poultry diets provide an opportunity to formulate more efficient reduced-crude protein diets [2, 3]. The energy demand of the small intestine is notably high which is partially due to the rapid renewal of the epithelium to maintain its function [4, 5] Both amino acids, especially glutamate and glutamine, and glucose undergo catabolism in avian enterocytes to generate energy [6]. There are indications in poultry that slowly digestible starch spares amino acids from catabolism [3] which is of particular importance for reduced-crude protein diets which axiomatically contain more starch than standard broiler diets
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