Failure of excess leucine to impact live performance and carcass traits in male and female Cobb MV × 500 broilers during a 15- to 32-day grower period

Abstract

Summary: Modern broiler diets may contain excess levels of leucine due to the increased level of this amino acid in cereal grains. Excessive levels of leucine have previously been shown to negatively influence broiler performance due to branched-chain amino acid antagonism. Therefore, 2 leucine titrations were conducted in male and female Cobb 500 broilers. Low and high leucine diets were formulated to contain leucine to lysine ratios of 115 and 170, respectively. These diets were subsequently blended to produce 6 experimental diets containing leucine to lysine ratios of: 115, 126, 137, 148, 159, and 170. Pelleted diets were fed to 8 replicate pens of male and female broilers during a 15 to 32-day period. A subset of broilers was processed on day 33 for determination of carcass traits. Male broilers did not respond to excessive levels of dietary leucine. Increased leucine resulted in a positive quadratic response (P = 0.020) in feed intake for female broilers. The overall lack of a response of increased dietary leucine on male and female broilers indicate that industry levels of isoleucine and valine are likely of a sufficient level to overcome the effects of leucine excess.

Keywords

• antagonisms
• feed conversion
• breast meat yield