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

A study was conducted to evaluate the relationship of dietary Lys and other essential amino acids (EAA) in diets for broilers. Diets were formulated based upon NRC (1994) recommendations. Within each age period, diets contained NRC recommended levels of Lys with other EAA at 100, 110, 120, or 130% of NRC. The diets were then supplemented with 0.1, 0.2, or 0.3% additional Lys, resulting in a 4 x 4 factorial arrangement with four levels of Lys (NRC, + 0.1%, + 0.2%, and + 0.3% Lys) and four levels of other EAA (100, 110, 120, and 130% of NRC). Each of the 16 treatments was fed to six replicate pens of 25 male broilers of a commercial strain. At 56 d, five birds per pen were processed to determine dressing percentage and carcass yield. There were no significant interactions between level of Lys and levels of other EAA for live performance or carcass characteristics. The BW was significantly increased at 21 and 42 d by addition of + 0.1% Lys above NRC but not at 56 d. There was no significant effect of other EAA on BW at any age. The effects of Lys on feed conversion were varied. At 21 and 42 d, addition of 0.1% Lys to diets containing the NRC Lys level significantly improved feed conversion; response to 0.2 or 0.3% Lys were varied. No significant effects 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, breast meat yield, or abdominal fat content. The level of other EAA significantly influenced dressed yield but had no significant influence on carcass yield. These results indicate that NRC (1994) levels of Lys and other EAA are adequate for optimum performance of male broilers processed at 56 d but may be less than adequate at younger ages.