Effects of increasing levels of dietary L-Leucine on growth performance, carcass traits and blood parameters of male broilers in the grower period

The effects of increasing levels of L-leucine supplementation on performance, carcass traits, breast meat production and determination of digestibleleucine requirement broilers during the grower period (15 to 30 days) using 240 Ross males broiler chickens in a completely randomized design withsix dietary treatments (five repetitions and eight chicks per repetition) was investigated. Treatments include; a basal diet with 1.53% digestible leucineand five diets containing 1.63, 1.73, 1.83, 1.93, and 2.03% digestible leucine by adding synthetic L-leucine to the basal diet. By increasing the levels ofdigetible Leucin, body wieght gain, carcass and breast muscle percentage were increased, but feed conversion ratio and abominal fat percentage weredecreasd (P<0.05). The response trends to increasing levels of digestible leucine were quadratic for weight gain, feed conversion ratio, the relativeweight of carcass, relative weight of breast muscle and relative weight of abdominal fat ( P<0.05). Due to the better fit of the quadratic model to theresponse criteria, digestible Leucine requirements were estimated at 1.70, 1.72, 1.724, and 1.735% for body weight gain, feed conversion ratio, therelative weight of carcass and breast muscle; respectively. Based on the average of these estimates, the suggested digestible Leucine requirements ofbroilers in the grower period is 1.72%.