Repeatability of blood progesterone levels in embryo transfer recipients

Abstract

This study involved 64 Holstein-sired crossbreds, 64 Brown Swiss-sired cross-breds, and 20 daughters of crossbred sires. These were compared to contemporary Holsteins. The females were sired by 24 Holstein and 18 Brown Swiss bulls selected from AI studs, and four crossbred sires produced in the herd. The mean deviations of crossbreds from the age-adjusted five-month rolling herd average of contemporary Holsteins were: -86, -498, and -1,173 kg of milk for Holstein-sired crosses, Brown Swiss-sired crosses, and daughters of crossbred sires, respectively. The purebred-sired crosses were significantly superior (P < 0.01) to daughters of crossbred sires; and Holstein-sired crosses were superior (P < 0.01) to Brown Swiss-sired crosses. The Holstein-sired crosses surpassed all other breed groups for yields of milk fat, solids-not-fat, protein, fat-corrected milk, and solids-corrected milk, but all groups produced similar yields of fat-corrected milk per unit body weight. The crosses were slightly higher than Holsteins in per cent protein and 0.45% higher in per cent milk fat and solids-not-fat. Differences among breed groups for length of lactation, persistency of lactation, and days carried calf were not important. Purebred-sired crossbreds had from 4 to 16% positive heterosis for milk yield, 0 to 7% for milk fat, and 1 to 10% for fat-corrected milk, but ranged from 1% above to 8% below the parental mean in per cent milk fat. Estimates of heterosis for three-breed crosses were higher than for two-breed crosses. Deviations from the parental mean for daughters of cross-bred sires were negative for all production traits.