title: Variances, repeatabilities, and age adjustments of yield and fertility in dairy cattle.
abstract: Breeding receipts from artificial insemination were matched with records of milk yield from northeastern United States. Nine measures of yield and 10 measures of fertility were investigated. A completely random model with herd-year-season, sire, and interaction of sire by herd-year-season was applied by parity; interaction of sire by herd-year-season was not important except possibly for fertility of virgin heifers. Sires accounted for 6 to 7% of yield variation and herd-year-seasons accounted for about 45%. Measures of fertility had small sire variances, and herd-year-season variance was much smaller than for yield. Effects of age within parity were significant for yield from ordinary least-squares analysis. Age adjustment factors were obtained for measures of yield. Repeatabilities of first- and second-parity yield ranged from .40 to .61 whereas repeatabilities of fertility were .03 to .13. Repeatabilities of virgin heifer and first-parity fertility were .01 to .03, suggesting heifer and cow fertility may not be related.
mesh_terms: D000367:Age Factors; D000818:Animals; D001947:Breeding; D002417:Cattle / Q000502:physiology*; D005260:Female; D005298:Fertility; D007315:Insemination, Artificial / Q000662:veterinary; D007774:Lactation; D008892:Milk / Q000378:metabolism; D008954:Models, Biological; D010298:Parity