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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 #145639
Title: USE OF CUBIC SPLINES FOR ESTIMATING LACTATION CURVES OF HOLSTEIN COWS TREATED WITH BOVINE SOMATOTROPIN

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

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 2/2/2003
Publication Date: 4/1/2003
Citation: Degroot, B.J., Keown, J.F., Kachman, S.D., Van Vleck, L.D. 2003. Use of cubic splines for estimating lactation curves of Holstein cows treated with bovine somatotropin [abstract]. 15th Annual Kansas State University Conference on Applied Statistics in Agriculture. p. 9.

Interpretive Summary:

Technical Abstract: Cubic splines can be used to model fixed and random effects of lactation curves. A total of 64,138 test-day observations for first lactation Holstein cows recorded as treated with bovine somatotropin (bST) and 138,008 test-day observations for untreated cows were obtained from Dairy Records Management Systems in Raleigh, North Carolina for the analysis. A cubic spline model was used to fit a population lactation curve and specific curves for each animal for both random genetic and permanent environmental components. Estimates of genetic, permanent environmental, and residual (co)variance components were obtained with REML. The overall lactation curve and magnitude of response to bST was measured between treated and untreated cows. The bST treated cows were recommended to receive the treatment at about day 50 of lactation. The 2.7 kg difference between treated and untreated cows at day 100 was maintained until about day 250 of lactation.