Methionine hydroxy analog supplementation of low protein calf rations

Thirty-six Holstein calves were randomly assigned at 3 days of age to one of three complete calf rations: ration A, B, C containing 0, .25, or .50% methionine hydroxy analog. All three rations were isonitrogenous at 13.5% crude protein (dry basis) and were offered adlibitum until calves were 12 wk of age. Calves were fed 3.64 kg whole milk oncedaily for 4 wk. Average daily gains (kg) and dry matter intakes (kg) from 4 to 12 wk were .88, 2.49; .77, 2.50; and .56, 1.98 for calves fed A, B, and C. Weight gains differed between all rations while intake was higher for A and B than for C. Dry matter intakes (kg per kg gain) from 4 to 12 wk were 2.85, 3.32, and 3.54. Serum amino acids for five calves on each treatment were similar for A and B. Calves fed C had lower serum values for all individual essential amino acids compared to A and B and 28% lower circulating total essential amino acids. Serum cysteine increased as dietary methionine hydroxy analog increased. Anamino acid imbalance or toxicity may have been produced which severely reduced gain, intake, and serum amino acids on ration C but only reduced gain on ration B.