Influence of Three Concentrations of DL-Methionine or Methionine Hydroxy Analog on Milk Yield and Milk Composition

Sixty-eight Holstein cows were fed diets consisting of 60% concentrate and 40% forage, dry basis. Diets were supplemented with DL-methionine or methionine hydroxy analog at either 0, .1, .2, or .3% of the concentrate. Dietary protein averaged 14% of total dry matter on all diets except for a positive control diet, which was 19% crude protein. Data were collected beginning 4 d postpartum and continued through 116 d postpartum. Milk yield was not influenced by either DL-methionine or methionine hydroxy analog. Supplementation with DL-methionine resulted in a quadratic response in milk fat percentage (3.34, 3.58, 3.72, 3.42) at 0, .1, .2, and .3% of the concentrate, respectively. Milk fat percentage increased linearly (3.34, 3.64, 3.60, 3.73) with supplementation of methionine hydroxy analog at 0, .1, .2, and .3%, respectively.