Comparative Efficiency of Feed Utilization During First Lactation of Ayrshire, Brown Swiss, and Holstein Cows

Abstract

First-lactation data on 57 Ayrshire, 68 Brown Swiss, and 57 Holstein cows, milked contemporarily in the Beltsville herd between 1958 and 1966, were studied to estimate inter-breed differences in feed efficiency and intra-breed relations of feed efficiency to body size, weight, and weight gain. The foundation cows of this group, and the sires of all cows were selected so that the 182 cows studied constituted representative cross-sections of the genetic pool of registered cows in Dairy Herd Improvement Association herds. Daily records were kept on each cow's feed consumption and milk yield. Feed and milk were evaluated using U.S. average prices. Body size of each cow was measured at 30 months of age. Phenotypic correlations indicated a high positive relation between efficiency and various measures of production and income, and uniformly negative relations between efficiency and mean body weight, gain in weight, and four measures of body size. The data were fitted to least-squares models which included breed, year and season of calving, and various combinations of the body weight and size variables (linear and quadratic). Adjusting only for breed, year, and season of calving, the mean feed efficiencies were 60.3% for Ayrshires, 54.3% for Brown Swiss, and 61.0% for Holsteins, indicating that the Brown Swiss were less efficient (P<.01) than Ayrshires or Holsteins. At a given body weight, chest girth or withers height, Holsteins were more efficient (P<.05) than the two other breeds. These results indicated that in all cases Holsteins were more efficient than Brown Swiss, with Ayrshires intermediate, the significance relationship depending on the model used. In most cases, when two of the body weight or size measures were used in the same model, a significantly better fit was obtained to the data than when either of the same two variables was used alone in the model.