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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Genetics and Animal Breeding » Research » Publications at this Location » Publication #141261
Title: ESTIMATES OF GENETIC PARAMETERS FOR FIRST LACTATION TEST-DAY YIELDS OF HOLSTEIN COWS WITH A CUBIC SPLINE MODEL

Author
item DEGROOT, BRUCE - UNIV. OF NEBRASKA-LINCOLN
item KEOWN, JEFFREY - UNIV. OF NEBRASKA-LINCOLN
item KACHMAN, STEPHEN - UNIV. OF NEBRASKA-LINCOLN
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 2/2/2003
Publication Date: 3/1/2003
Citation: Degroot, B.J., Keown, J.F., Kachman, S.D., Van Vleck, L.D. 2003. Estimates of genetic parameters for first lactation test-day yields of holstein cows with a cubic spline model. Journal of Animal Science 81(Suppl. 1):37.

Interpretive Summary: No interpretive summary is required.

Technical Abstract: The objective was to estimate genetic parameters for individual test-day milk, fat, and protein yields with a cubic spline model. A total of 196,687 test-day records in the first 305-d of 38,172 first lactation Holstein cows that calved between 1994 and early 1999 were obtained from Dairy Records Management Systems in Raleigh, North Carolina for the analysis. Estimates of the (co)variances for the cubic spline with five knots were obtained with REML. Estimates of heritabilities for test-days and estimates of genetic and phenotypic correlations between test-days were obtained from the estimates of variance and covariances from the cubic spline analysis. Genetic parameters were estimated at the average test day within each of the ten 30-d test day intervals. The cubic spline model included herd test-day and age at first calving as fixed effects. Cubic splines were fitted for the overall lactation curve, additive genetic effects, and permanent environmental effects. The cubic splines used five predetermined intervals between days 0, 50, 135, 220, and 305. Estimates of heritability for milk, fat, and protein yields ranged from 0.13 to 0.16, 0.09 to 0.13, and 0.11 to 0.16 for test-day one to test-day ten. Estimates of genetic correlations between test-days ranged from 0.98 to 0.60 for milk yield, 0.98 to 0.40 for fat yield, and 0.99 to 0.64 for protein yield. Estimates of phenotypic correlations between test-days ranged from 0.70 to 0.31 for milk yield, 0.52 to 0.23 for fat yield, and 0.65 to 0.26 for protein yield. The results indicated that estimates of heritability increased over the course of the lactation. Estimates of genetic and phenotypic correlations decreased for test-days further apart.