Methionine and Sulfur Amino Acid Requirement in the Preruminant Calf

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Abstract
Five quantities of dietary methionine were tested in 20 male Holstein calves (6-27 days of age) fed milk replacers (diluted to 13% solids) as the only feed in a 2-period changeover design. Amounts of methionine in diets were 1.86, 2.48, 3.10, 3.72 and 4.34 g/16 g N ingested. Of the 20% crude protein in replacer diets, 75% was from milk sources and 25% from a crystalline amino acid mixture which varied in methionine and non-essential amino acids glycine and glutamate. Daily gains were small during the experiment but were less on most methionine than for other treatments. Digestibilities of dry matter and crude protein averaged 83 and 66%. They were higher in period 2 (18-27 days) than in 1 (6-15 days) and lower on highest methionine than other diets. Most methionine also caused the greatest fecal excretion and the highest concentration of urea N in plasma. The expected linear increase in methionine of plasma after needs were met was replaced by plateauing at highest dairy methionine. Optimum methionine intakes, predicted from regression analyses of daily gains, N retention, and concentrations in plasma methionine, ranged from 2.75-2.95 g/16 g ingested N. All diets contained 1.05 g cystine/16 g N, thus if cystine can replace up to 55% of the methionine needs as for the other species, the need for total amino acids containing S in the baby calf is 3.8-4.0 g/16 g N. Three days on diets appeared sufficient for predicting methionine requirements from methionine of plasma.