Nine measures related to breeding efficiency were used for comparisons among purebred Ayrshires, Brown Swiss, Holsteins, and Jerseys and between purebreds and 32 crossbred groups representing 2-breed, 3-breed, 5/8, and backcrosses by purebred sires and progeny of crossbred sires. There were four herds with Holsteins common to all, Brown Swiss and Jerseys in three herds and Ayrshires in one herd. Four 2-breed, two 3-breed, and two backcross groups were common to two or more herds. Among purebreds, breed effects were significant in 16 of 72 tests, but there was no consistent trend favoring one breed. Generally, Jerseys were better than Holsteins, and Brown Swiss were poorer than Holsteins. Purebred females bred to their breed required similar services for conception (1.77 versus 1.79) as when bred to a different breed of sire. Least squares estimates of differences between purebreds and crossbreds favored crossbreds in 86 of 144 tests suggesting advantages for breeding efficiency; however, few were significant. Standard errors frequently exceeded estimates of differences. Parity was not associated with superiority in the crosses.
This study was to determine if breed groups ranked differently in warm (May to August) and cool (November to February) seasons of calving and to determine if heterosis was more important in the warm season. A total of 719 records of cows in first lactation in four herds in the southeastern United States were used. Breeds were Holsteins, Brown Swiss, and Jerseys and the crosses among them. Milk and milk fat yields were greater in the cool season than in the warm season. Holsteins exceeded other breeds for milk and milk fat yield in both seasons, but their superiority was less among cows calving from May through August. Days open were longer for Holsteins, particularly in the warm season. In the cool season only the 3/4 Holstein X 1/4 Swiss group exceeded Holsteins for milk, but two groups--1/2 Holsteins X 1/2 Swiss and 5/8 Holstein X 1/4 Swiss-1/8 Jersey--were higher in the warm season. In the cool season three crossbred groups--1) 1/2 Holstein X 1/2 Swiss (Holstein sires), 2) 3/4 Holstein X 1/4 Swiss, and 3) 1/2 Holstein X 1/4 Swiss-1/4 Jersey--had greater milk fat yields than Holsteins, and a fourth--1/2 Holstein X 1/2 Jersey--yielded an equal amount. In the warm season six of the eight crossbred groups had greater milk fat yields than Holsteins. More crossbreds exceeded Holsteins in the warm than in the cool season, suggesting interactions for yields. There was slightly more heterosis in warm than in cool seasons for all traits.
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