EFFECTS OF AMINO-ACID RESTRICTION DURING STARTER AND GROWER PERIODS ON SUBSEQUENT PERFORMANCE AND INCIDENCE OF LEG DISORDERS IN 2 STRAINS OF MALE LARGE WHITE TURKEYS

Male turkeys of two commercial Large White strains (Nicholas 88, BUT 6 ) were subjected to growth restriction by means of reducing amino acid (AA) content of diets to a minimum of 75% of NRC (1994) suggested lev els. There were three periods when diets containing 75% of NRC recomme nded AA for that age period were fed aii libitum: 0 to 3 wk, 0 to 6 wk , or 6 to 12 wk. A fourth (control) group was not restricted in AA con tent at any time. When turkeys were not fed the AA-restricted diets th ey were fed diets formulated to meet a minimum of 100, 110, or 120% of NRC (1994) AA recommendations, which resulted in a 3 x 4 factorial ar rangement of treatments with three AA levels by four restriction times . Four pens of 12 males each were fed each AA by restriction time comb ination. At 18 wk, all birds were scored individually for leg conditio n and representative samples of turkeys were processed for parts yield . Birds fed restricted diets from 0 to 6 or 6 to 12 wk had significant ly lower BW at 18 wk than control birds. Birds fed the restricted diet s from 0 to 3 wk did not differ significantly in 18-wk BW compared to control birds but the magnitude of difference was similar to that obse rved at the end of the restriction period. Feed utilization was not im proved by early AA restriction. Restricting early growth resulted in a significantly higher incidence of birds with no leg disorders and a l ower incidence of birds with moderate leg disorders than control birds . Feeding higher AA levels during realimentation resulted in a greater severity of leg disorders. Breast meat yield was depressed significan tly as severity of early restriction increased. Increasing dietary AA above NRC (1994) recommended levels generally improved performance dur ing realimentation but was not able to compensate for reduced gains du ring restriction.