Relationship of dietary lysine level to the concentration of all essentialamino acids in broiler diets

A study was conducted to evaluate the relationship of dietary Lys and other essential amino acids (FAA) in diets for broilers. Diets were formulated b ased upon NRC (1994) recommendations. Within each age period, diets contain ed NRC recommended levels of Lys with other EAA at 100, 110, 120, or 130% o f NRC. The diets were then supplemented with 0.1, 0.2, or 0.3% additional L ys, resulting in a 4 x 4 factorial arrangement with four levels of Lys (NRC , + 0.1%, + 0.2%, and + 03% Lys) and four levels of other EAA (100, 110, 12 0, and 130% of NRC). Each of the 16 treatments was fed to six replicate pen s of 25 male broilers of a commercial strain. At 56 d, five birds per pen w ere processed to determine dressing percentage and carcass yield. There were no significant interactions between level of Lys and levels of o ther EAA for live performance or carcass characteristics. The BW was signif icantly increased at 21 and 42 d by addition of + 0.1% Lys above NRC but no t at 56 d. There was no significant effect of other EAA on BW at any age. T he effects of Lys on feed conversion were vaned. At 21 and 42 d, addition o f 0.1% Lys to diets containing the NRC Lys level significantly improved fee d conversion; response to 0.2 or 0.3% Lys were varied. No significant effec ts of Lys on feed conversion were observed at 56 d. Increasing the level of EAA resulted in significant improvements in feed conversion at 21, 42, and 56 d, generally following a linear trend. Dietary Lys levels had no significant effects on dressing percentage, breas t meat yield, or abdominal fat content. The level of other EAA significantl y influenced dressed yield but had no significant influence on carcass yiel d. These results indicate that NRC (1994) levels of Lys and other EAA are a dequate for optimum performance of male broilers processed at 56 d but may be less than adequate at younger ages.