Lysine as a Modulator of Cottonseed Meal Inclusion Replacing Soybean Meal Protein in Diets for Slow-Growing Chickens at 56 and 77 Days of Age

This study evaluated the performance, carcass yield, and meat quality of slow-growing chickens fed diets containing different levels of replacement of crude protein from soybean meal with crude protein from cottonseed meal (CSM), with and without supplementation of 2% lysine. A total of 600 male chickens of the Red Colonial heavy strain were used and evaluated from 8 to 56 and to 77 days of age. In Experiment 1, chickens were fed diets with 0, 15, 30, and 45% replacement of soybean meal protein by CSM protein; in Experiment 2, the same replacement levels were associated with supplementation of 2% lysine based on the protein content of CSM. The 15% replacement level promoted higher live weight and average weight gain at 56 and 77 days. Feed conversion ratio at 56 and 77 days indicated that replacing soybean meal protein with CSM protein, with the addition of 2% lysine relative to the protein value, resulted in improved values for this variable. It is concluded that replacing up to 15% of soybean meal protein with cottonseed meal protein, with or without supplementation of 2% lysine, does not compromise productive parameters, carcass yield, or meat quality in slow-growing chickens.