Lysine Levels in Starter and Grower-Finisher Diets Affect Broiler Performance and Carcass Traits

Providing adequate dietary lysine (Lys) to broilers is critical if the amount of saleable white meat is the economic objective. However, the period when Lys is most critical for breast development remains unclear. The objective of this study was to determine if dietary Lys in the starter and grower-finisher diets interact to affect live performance, mortality, and breast meat in commercial broilers. This study records two levels of Lys in the starter diets (95 and 115% of 1994 NRC) and three levels of Lys in the grower-finisher diets (85, 105, and 125% of 1994 NRC) fed to male broilers in diets composed of corn, soybean meal, corn gluten meal, poultry meal, and poultry oil. Increasing Lys in the starter or grower-finisher diet increased both performance and mortality. Breast meat weight and yield increased when broilers received the highest Lys levels in the starter and grower-finisher diets. Feeding broilers inadequate dietary Lys in the starter period decreased finishing live performance and breast meat responses, irrespective of grower-finisher Lys levels. Dietary Lys levels above that considered adequate (125% of 1994NRC) in the grower-finisher diets compensated for loss of breast meat due to Lys inadequacy in the starter diet, but compensatory breast meat accretion was not complete.