Evaluating the digestible lysine requirements of male Cobb MV × Cobb 500 broilers during the first fourteen days of age and the carryover effect of feeding varying levels of digestible lysine on performance and processing

Digestible lysine (dLys) requirements in broilers is heavily researched due to lysine's importance in diet formulation, body protein accretion, and dietary protein cost. As such, when novel broiler strains are established, it is important to evaluate their dLys requirements. The current objective was to determine the dLys requirement of male Cobb MV × Cobb 500 broilers from d 0 to 14 and evaluate the carryover effect (d 14–41) of feeding varying starter levels of dLys. Two basal diets were formulated (0.88% dLys and 1.44% dLys), then blended to create 6 intermediate dLys treatments (ranging from 0.96 to 1.36% dLys), creating a total of 8 dLys experimental diets. A control diet (treatment 9–1.28% dLys) was separately made to confirm blending techniques. Treatments were arranged as a randomized complete block design (RCBD) to 96 pens, with each pen having 14 male chicks. In general, increasing dLys resulted in improvements in performance metrics and processing weights. From d 0 to 14, feeding ≥1.20% dLys increased BW and BWG, feeding ≥0.96% dLys increased FI, with an exception in birds fed 1.44% dLys; stepwise reductions in FCR were observed as dLys increased from 0.88 until 1.20% dLys. Estimated dLys requirements ranged from 1.17 to 1.30% for BWG and 1.29 to 1.49% for FCR (using multiple regression methods). In general, carryover effect data (d 0–41) demonstrated that increasing starter dLys improved performance and d 42 processing. Future research should evaluate higher dLys levels than those used in this study and the dLys requirements of female Cobb MV × Cobb 500 broilers during the starter phase.