The influence of differences in dietary amino acids during the early growing period on growth and development of Nicholas and British United Turkey toms.

From 0 to 4, 4 to 8, and 8 to 12 wk of age, Nicholas (NIC) and British United Turkeys (BUT) toms were fed one of two series of experimental diets. All toms were fed the same diet, appropriately adjusted for age period, from 12 to 16 and 16 to 24 wk. The first series was formulated to 1984 NRC specifications whereas the second series contained higher concentrations of lysine and total sulfur amino acids (NRC+). The NIC toms were heavier (P < or = .05) at 4, 8, 12, and 16 wk, but there were no strain differences at 20 wk. The NRC+ diets significantly increased BW in both strains at 12 wk, but there were no diet effects at 16 or 20 wk. At 12 wk, BUT toms had significantly more carcass protein and less carcass lipid compared with NIC toms, but there were no significant dietary effects on these variables. In both strains, the NRC+ diets significantly increased the relative weight of the eviscerated carcass and both the absolute and relative weights of the Pectoralis major muscles at 12 wk. At 20 wk, the absolute and relative weight of the Pectoralis minor muscles was significantly heavier in BUT toms and in toms fed the NRC+ diets. The tibia and femur were longer in BUT toms compared with NIC toms. From 1 to 24 wk, weekly BW from 50 toms per strain and treatment combination were used to calculate growth curve parameters according to the Gompertz equation. The slope of the growth curve was significantly less in BUT toms, but the BW and age at the point of infection were increased compared with NIC toms. There were no significant diet effects on any growth curve parameters.