Evaluation of N-Hydroxymethyl-DL-Methionine-Ca and Di-Hydroxymethyl-L-Lysine-Ca in a Blended Corn Based Ration for Lactating Cows

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Abstract
Five lactating cows were fed ad lib a ration of 67% corn silage and 33% concentrate and 2.2 kg hay/head daily in a 5 .times. 5 Latin square to evaluate 5 treatments: negative control; 64 g/day di-hydroxymethyl-L-lysine-Ca; 24 g/day N-hydroxymethyl-DL-methionine-Ca; 64 g/day di-hydroxymethyl-L-lysine-Ca and 24 g/day N-hydroxymethyl-DL-methionine-Ca; and 638 g/day formaldehyde-treated sodium caseinate. N supplements were blended with the corn silage and concentrate at time of feeding. Dry matter of the basal ration contained 11-12% crude protein. Mean daily milk yields were 27.4, 26.9, 26.1, 27.1 and 29.9 kg for the respective treatments. Yields of milk, milk protein and milk fat and efficiency of feed conversion to 4% fat-corrected milk were greatest with formaldehyde-treated casein. Amino acid derivatives had no effect on feed intake, milk production, milk composition or utilization of dietary N. Concentrations of methionine and lysine in plasma, relative to the other indispensable amino acids, were not different among treatments. The low pH of the ration probably resulted in considerable dissociation of the derivatives prior to consumption.