Abstract: There is scanty of information on Threonine (Thr) requirements of mixed-sex broiler chickens during the grower period. An experiment was conducted to determine the digestible Thr requirements of straight-run Ross 308 broilers from 15-28 days of age. Basal diet consisting of wheat, triticale and corn gluten meal was formulated to meet or exceed the nutrient requirements except for Thr. Graduation levels of supplemental Thr were added to the basal diet at expense of corn starch generating six treatments to provide a range from 0.46-0.81% of digestible Thr. Both male and female birds were randomized across 48 floor pens (4 replicates and 12 birds per each replicate) in a completely randomized design and each pen was fed one of six amino acid levels from 15-28 days of age. Body weight gain, feed intake, feed conversion, digestible Thr intake and mortality were measured during the experimental period. Body Weight Gain (BWG) and Feed Conversion (FC), Feed Intake (FI) and daily Thr intake responded quadratically to graded levels of digestible Thr (0.46-0.81% of diet). Digestible Thr requirements were estimated using a linear broken-line and quadratic broken-line models. Based on broken-line linear model, digestible Thr requirement for straight-run Ross 308 broilers was determined to be 0.69 and 0.76% for BWG and FC, respectively. However, using broken-line quadratic model, digestible Thr was estimated at 0.79% for BWG.

Keywords