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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 #146179
Title: ESTIMATES OF GENETIC PARAMETERS AND LACTATION CURVES WITH A CUBIC SPLINE MODEL FOR HOLSTEIN COWS TREATED WITH BOVINE SOMATOTROPIN

Author
item DEGROOT, B. - UNIV. OF NEBRASKA-LINCOLN
item KEOWN, J. - UNIV. OF NEBRASKA-LINCOLN
item KACHMAN, S. - UNIV. OF NEBRASKA-LINCOLN
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/2003
Publication Date: 7/1/2003
Citation: DeGroot, B.J., Keown, J.F., Kachman, S.D., Van Vleck, L.D. 2003. Estimates of genetic parameters and lactation curves with a cubic spline model for holstein cows treated with bovine somatotropin [abstract]. Journal of Dairy Science 86(Suppl. 1):37.

Interpretive Summary:

Technical Abstract: The objective was to estimate genetic parameters and response to bovine somatotropin (bST) from individual test-day milk yields with a cubic spline model for first three lactations. A total of 263,034 test-day milk records of Holstein cows treated with bST and 405,265 test-day records of untreated cows that calved between 1996 and early 2002 were obtained from Dairy Records Management System, Raleigh, North Carolina. Estimates of (co)variances for a 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 estimates of variances and covariances from the cubic spline analysis. Genetic parameters were estimated at the average day within each of the ten 30-d test day intervals. The cubic spline model included herd test-day, age at first calving, treatment, and treatment by linear as fixed effects and treatment by spline as random effects. Cubic splines were fitted for the overall lactation curve within treatments, additive genetic effects, and permanent environmental effects. The cubic splines used five intervals determined by days 0, 50, 135, 220, and 310. The treatment differences were measured for bST treated and untreated cows. Estimates of heritability for test-day one to test-day ten ranged from 0.09 to 0.16, 0.10 to 0.17, and 0.10 to 0.18 for lactations one, two, and three. Estimates of genetic correlations for milk yield at pairs of test-days ranged from 0.99 to 0.45 for lactation 1, 0.99 to 0.32 for lactation 2, and 0.99 to 0.35 for lactation 3. The differences of 3.17, 2.27, and 2.30 kg between treated and untreated cows at day 100 were maintained until about day 220 of lactations one, two, and three. Estimates of heritability increased over the course of the lactation and estimates of genetic correlations decreased for pairs of test-days further apart.