Identification of limiting amino acids in methionine- and lysine-supplemented low-protein diets for turkeys.

Large White male turkeys were fed 100, 85, 70, or 60% of NRC (1994) CP during 7 to 28 d (Experiment (EXP) 1), 8 to 12 wk (EXP 2), and 16 to 20 wk (EXP 3) of age. Diets contained corn, soybean, canola, and meat meals and were supplemented with Met and Lys to requirement. The influence of supplementary amino acids (AA) was studied at each protein level. Turkeys fed 85% CP gained BW similarly to those fed 100% of NRC CP (control) during each age range. Supplemental Thr, Val, and Ile during 7 to 28 d or 8 to 12 wk, or Thr during 16 to 20 wk, did not result in positive BW gain response. For turkeys fed 70% CP, BW gain was depressed compared with the normal-CP control in each period. During 7 to 28 d and 8 to 12 wk of age, the combination of Thr, Ile, Val, Arg, and Trp to 100% of NRC reversed the BW depression; here only Thr, Ile, and Val were essential components of the response. The BW depression during 16 to 20 wk was reversed by the combination of Thr, Ile, Val, and Trp. For turkeys fed 60% of CP, BW gain was severely depressed. The combination of Thr, Ile, Val, Trp, and Arg resulted in nearly complete BW recovery during each age.