Production of Milk and Milk Constituents by Brown Swiss, Holsteins, and Their Crossbreds

Abstract

Least squares procedures were used to evaluate yields by crossbred and back-cross Brown Swiss and Holstein in relation to purebred contemporaries many of which were paternal or maternal half-sisters. Foundation females were taken at random from groups of females in the University herd. Bulls, 16 Brown Swiss and 13 Holstein selected at random from bulls in 13 artificial insemination studs, sired the crossbreds and purebreds. From foundation cows, were 34 Holsteins, 26 Brown Swiss, and 13 each of the Holstein x Swiss (breed of bull first, breed of cow last.) and Swiss x Holstein crosses that completed first lactations. First-generation purebreds were bred for purebreds and crossbreds, and crossbreds were bred for backcrosses. Both first-generation crossbred groups had fewer days open than purebreds. Numbers in second-generation groups with lactation records varied from 9 to 13. Crossbreds in each generation averaged higher than the purebreds for yields of milk, milk fat, 4% fat-corrected milk, solids-not-fat, and protein. Interaction (sire-dam) constants were not significant; neither was heterosis for production traits. For days open these estimates ranged from 14 to 31%.