Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/17/2006
Publication Date: 7/9/2006
Citation: Norman, H.D., Wright, J.R., Powell, R.L., Van Raden, P.M., De Jong, G. 2006. Genetic differences between maturity rates of daughters of Holstein bulls in the Netherlands and United States [abstract]. Journal of Dairy Science. 89(Suppl. 1):16-17(abstr. M29). Interpretive Summary:
Technical Abstract: Maturity rate of Holstein bull daughters in the Netherlands and United States were compared by examining sire predicted transmitting abilities (PTA) for milk yield for each of the first 3 parities. For each bull with US daughters, PTA that included data from parity 1 (PTA1), parities 1 and 2, and parities 1 through 3 were calculated from US milk records of cows with first-parity calving dates between 1960 and 1998. Using those PTA, PTA for contributions from only parity 2 (PTA2) and parity 3 (PTA3) were estimated based on numbers of daughters with first, second, and third parities. Parity-specific Dutch estimated breeding values (NLD1, NLD2, and NLD3) were from August 2005 evaluations. To determine whether maturity-rate differences were genetic, comparisons were made across generations. Coefficients for regression of son PTA on sire PTA calculated within sire and son birth years for PTA1, PTA2, PTA3, PTA2 - PTA1, PTA3 - PTA1, and PTA3 - PTA2 were 0.42 to 0.47; most had standard errors of 0.01. Similar regression coefficients for Dutch evaluations were 0.35 to 0.50. Maturity rate of Dutch daughters was compared with that of US daughters for the same bull. Correlations among parity-specific bull evaluations were calculated within birth year of bulls. Correlations for 2850 bulls with >=500 US daughters were 0.88 between PTA1 and PTA2, 0.84 between PTA1 and PTA3, and 0.96 between PTA2 and PTA3; corresponding correlations for Dutch evaluations of 269 bulls were 0.92, 0.89, and 0.98, which are considerably higher than parity correlations assumed in the Dutch evaluation model. Correlations between PTA2 - PTA1 and NLD2 - NLD1 was 0.66 for 539 bulls with >=50 daughters and 0.82 for 93 bulls with >=500 daughters. Corresponding correlations were 0.61 and 0.83 between PTA3 - PTA1 and NLD3 - NLD1 but much lower (0.18 and 0.70) between PTA3 - PTA2 and NLD3 - NLD2. Differences in maturity rate of bull daughters were quite consistent across countries and transmitted to granddaughters in both countries through bull sons. Accounting for maturity differences should increase evaluation accuracy for bulls that deviate substantially from population mean.