Growth performance and small intestinal morphology of native chickens after feed supplementation with tryptophan and threonine during the starter phase

The amino acid content of feed can affect growth performance of poultry during the first 6 weeks of life or the starter phase. Unlike for broiler and layer chickens, there is no information concerning standard requirements for tryptophan and threonine during the starter phase. This study aimed to determine the amount of threonine and tryptophan that should be supplemented in chicken feed to maximize growth performance and small intestinal morphology of native chickens during the starter phase. A total of 128 day-old native chickens were divided into four treatment groups with four replications based on a completely randomized design. The treatment diets were as follows: T (control feed); T (T +0.10% L-tryptophan+0.35% L-threonine); T (T +0.17% L-tryptophan+0.68% L-threonine); and T (T +0.25% L-tryptophan+1.00% L-threonine). The feed intake was highest for the T and T groups (123.06 and 124.18 g/bird/week, respectively). The T group had the highest body weight gain (49.35 g/bird/week) and carcass weight (201.44 g/bird) relative to the other groups, while the T and T groups showed similar, significant (p