Vol. 9, Issue 8, Part B (2025)

A total of 250 commercial broiler birds (Ven Cobb) were used in the present research to assess the digestible threonine graded concentrations (100, 75, 70, 65, and 60% of the digestible lysine) in order to optimize the threonine requirements for improving the productive performance in commercial broiler diets. Using a completely random design (CRD) the chicks were divided into five treatments, each containing ten replicates and each with five chicks. Throughout the experiment, a corn soy based diet was prepared and supplemented with digestible threonine at graded concentration of digestible Lysine. The amount of digestible threonine in the broiler diet had no effect on feed intake and body weight gain in any of the growth phases. However, during the pre-starter and starting phases, FCR was significantly (p<0.05) influenced, with the supplemented groups at 65% and 60% showing better FCRs. While there was no difference in the slaughter parameters such as the heart and gizzard throughout treatment groups, the liver weight was considerably (p<0.05) lower in the 65 and 60% Thr groups than in all other threonine concentrations. Immune organ (spleen and bursa) weights, humoral immunity as measured by antibody titers to NDV, and cell mediated immunity as determined by PHA-P were unaffected by treatment groups. Thus, it can be concluded that in fast-growing commercial broilers, digestible threonine concentrations at 60% of the digestible lysine (0.708, 0.630, and 0.570%, respectively) during the pre-starter, starter, and finisher phases are ideal for improved growth performance without having any negative impact on carcass and immune parameters.