Interactive effects of lysine and threonine on live performance and breastyield in male broilers

The TSAA, lysine (Lys), and threonine (Thr) are considered to be the first three limiting amino acids, respectively, in a corn-soybean meal diet fed t o broilers. Recent data have clearly demonstrated that feeding broilers die ts containing higher than recommended levels of Lys improves broiler perfor mance and edible meat production. In contrast, there is limited data concer ning the Thr nutrition of modern broilers selected for breast meat yield. B ecause essential amino acids are known to interact with one another to impr ove certain production functions, this experiment attempted to describe the relationship between dietary Lys and Thr. This experiment measured the eff ect of adequate and super-adequate levels of dietary Lys as affected by Thr concentrations ranging from deficient to super-adequate. Increasing the co ncentration of dietary Lys from 105% to 120% of the NRC recommendation impr oved body weight gain, feed conversion, carcass yield, breast meat weight, and breast meat yield. Regardless of dietary Lys concentration, increasing dietary Thr from 85% to 92.5% of the NRC recommendation appeared to be adeq uate for broiler body weight gain and feed conversion. Dietary Lys and Thr interacted on breast meat weight (P < .10) so that 100.0% of the NRC recomm endation for Thr was required to maximize breast meat deposition in broiler s fed the 105% Lys diets, but 107.5% Thr was necessary to maximize breast m eat in broilers fed the 120% Lys diets.