Amino acid nutrition and chicken gut health

There is considerable interest in the development of reduced protein diets with supplemental amino acids (AAs) for broiler chickens due to economic, environmental, health and bird welfare advantages. Lowering levels of protein, or using local sources, which may be more poorly digested or have an unbalanced AA profile, has implications for both animal performance and health. However, reduced protein diets may result in AA redistribution away from growth and production processes, towards intestinal cells involved in immune and inflammatory responses. Certain gut diseases are related to higher protein diets, and low protein formulations can reduce the risk of such problems. However, in low protein diets, a reduced or unbalanced supply of AA in the diet can be deleterious to the immune system. Therefore, an ideal dietary AA profile is crucial for broiler chicken gut health, especially in Antibiotic growth promoter (AGP) free situations. All AA are in ratio to dietary Lys, and when Lys concentration is increased, both essential and non-essential AA concentrations need to be increased accordingly. Currently when dietary standardised ileal digestibility (SID) for Lys is 1.3%, the SID of total sulphur-containing AA may need to increase to 0.975%, Arg to 1.43%, Thr to 0.884%, Val to 1.04%, Ile to 0.884% and Phe to 0.845%. In wheat-soy based diets, reduced protein diets may lead to deficiencies in His and Ala, potentially affecting chicken gut health. Possibly the SID of His needs to increase to 0.53%. Some non-essential AA profiles need to increase, such as SID of Gly to 0.884%, Glu to 3.54% and Ala to 0.845%. Compared with DL-Methionine and DL-HMTBA, L-Met is the natural form of Met and its relative biological value has remained controversial due to unsuitable statistical models and other limiting AA influence. Increasing AA levels in reduced protein diets has been shown to maintain growth and ensure less incidence of gut disorders.