Estimation of Standardized Ileal Digestible Lysine Requirement of Starting Broiler Chicks Fed Soybean-and Cottonseed Meal-Based Diets

The research was conducted to determine the Standardized Ileal Digestible Lysine SID Lys) requirement of male broiler chicks from 0-14 days of age and to study the carry-over effects of early Lys deficiency in growing chickens. In the starter, graded levels of SID Lys in the experimental diets were achieved by addition of Lysine-HCl at the expense of cornstarch obtaining dietary SID Lys ranging from 0.88-1.28% of diet. Linear regression analysis was significant (p<0.05) for Body Weight Gain. (BWG), Feed Intake (FI), Breast Meat (BM) and Thigh Yield (THG) to dietary Lys. Both of Linear Broken-Line (LBL) and Quadratic Broken-Line (QBL) models were fitted to determine SID Lys requirement. Regarding response criteria and regression models, SID Lys requirements of starting broiler chicks were from 1.06-1.29% of diet. Assuming 83% lysine digestibility of basal diet, the requirements were 1.28-1.55% of diet on total amino acids basis which were much higher than NRC recommendations. From 14-28 days of age, chickens were fed common grower diet according to NRC. Linear regression analysis was significant for BWG, Feed: Gain (FG), BM and TGH yield (p<0.05). Early lysine deficiency significantly reduced BWG, feed efficiency, BM and TGH yield (p<0.05). This study clearly showed that the very lysine-deficient fed chickens could not mount a compensatory growth.