the effect of l-threonine supplementation of wheat based diet on performance, reproductive and internal organs and feathers growth in japanese quail

recent experiment was performed in order to determine effects of dietary l-threonine supplementation levels in japanese quails’ diets on performance, reproductive and internal organs and feathers growth. one hundred and forty four, 1-d old japanese quails, have been selected and randomly distributed between six treatments and four replicates. basal experimental ration was based on wheat, without supplemental threonine, and other treatments were supplied by 0.6, 1.2, 1.8, 2.4 and 3.0 g/kg l-threonine. the results have shown that body weight gain was improved by dietary threonine supplementation levels (p<0.05), but daily feed intake during 1-42 days and feed conversion ratio during 21-42 days of experiment did not shown significant differences between experimental groups. supplementation of l-threonine to quails’ diets decreased feed conversion ratio of birds during 1-21 and 1-42 days (p<0.05). experimental groups, have not significant difference on relative weight of heart, proventriculus, gonads and the relative length of ileum. relative weight of gizzard (p<0.05), abdominal fat and relative length of duodenum and jejunum increased by increasing threonine levels (p<0.01). decremental linear and quadratic trend by increasing threonine levels was observed in liver weight (p<0.05). cloacal gland volume were influenced by dietary l-threonine supplementation and increased by increasing threonine levels but has not significant effect on cloacal foam in male quails. supplementation levels of l-threonine have significant effect on increase feather length (p<0.01) and feather weight (p<0.05). supplementation 2.4 g/kg of l-threonine to quails’ diets improved body weight, feed conversion ratio and feather growth.