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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 #162189
Title: AN ANIMAL MODEL WITH AUTOREGRESSIVE COVARIANCE STRUCTURES AMONG RESIDUAL AND GENETIC EFFECTS FOR GENETIC EVALUATION OF HOLSTEIN COWS WITH TEST DAY RECORDS

Author
item SAWALHA, R. - UNIV. OF NEBR.-LINCOLN
item KEOWN, J. - UNIV. OF NEBR.-LINCOLN
item KACHMAN, S. - UNIV. OF NEBR.-LINCOLN
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2004
Publication Date: 7/26/2004
Citation: Sawalha, R.M., Keown, J.F., Kachman, S.D., Van Vleck, L.D. 2004. An animal model with autoregressive covariance structures among residual and genetic effects for genetic evaluation of Holstein cows with test day records [abstract]. Journal of Animal Science 82(Suppl. 1):84

Interpretive Summary: No interpretive summary is required.

Technical Abstract: This study was to evaluate an animal model with first order autoregressive covariance structures (AR1) among residual and genetic effects of test day (TD) records. This model was compared with a simple test day repeatability model and a 305-day lactation model. Data consisted of 106,472 test day records of 12,071 first lactation Holstein cows. Estimates of components of variance and autocorrelation coefficients were obtained for milk, fat, and protein yields and somatic cell scores (SCS) using ASReml. Likelihood ratio tests and AIC values indicated that AR1 model was significantly more appropriate for the TD data than the simple repeatability model for all four traits. Estimates of heritability were slightly lower for yield traits (0.09) with AR1 model than with simple TD repeatability model (0.10-0.11). Estimates of heritability with 305-d yield traits were in the range of 0.14 to 0.36. For SCS, both TD models resulted in similar estimates of heritability of 0.06. Estimates of residual variance were probably underestimated with simple repeatability model compared with AR1 model. Average estimates of accuracy of PBV for all traits were always higher with simple repeatability model than with AR1 model for both sires and cows. The least change in rank of the top 100 elite sires and cows was between the two TD models (4-9% for sires). The greatest difference in ranking of elite animals was between simple repeatability model and 305-d model (26-36% for sires). Similar patterns were also observed for values of correlation among PBV of different models. The AR1 model resulted in similar or slightly lower correlations between actual lactation records of cows and the averages of PBV of their parents compared with the simple repeatability model. Average PBV tended to increase with advancement of lactation for yield traits and to decrease for SCS. Averages of PEV of PBV were highest at the beginning and at the end of lactation.