Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/17/2006
Publication Date: 7/9/2006
Citation: Kuhn, M.T., Hutchison, J.L., Miller, R.H. 2006. Synchronization effects on parameters for days open [abstract]. Journal of Dairy Science. 89(Suppl. 1):15(abstr. M24).
Technical Abstract: The purpose of this research was to determine if synchronization affects parameters related to days open. If synchronization alters genetic or error variances, for example, adjustments could be made to the daughter pregnancy rate evaluations to account for these effects. Synchronization information on individual cows or herds is not currently available. Thus, a chi-square criterion, based on first service only, was used to distinguish between herds that are likely synchronizing and those that are not. Variances were estimated by REML for each group of herds using a linear model that included the effects of herd-year, year-state-month, parity, permanent environment, animal, and error. The genetic covariance between synchronized and non-synchronized records was estimated as well. There were 19,198 synchronized cows and 15,429 non-synchronized cows used for estimation. The genetic correlation between records classified as synchronized and those classified as non-synchronized was 1.0. However, some differences in variances were found. Genetic and permanent environmental variances were higher for non-synchronized records while error variance was higher for synchronized records, with the net effect of slightly higher heritability for non-synchronized records (0.04 vs 0.03) and higher repeatability for non-synchronized records (11.6% vs 5.7%). Preliminary results indicated only a slight improvement in sire PTA when days open records were adjusted for these differences in variances. Further research will focus on possible improvements for identifying herds using synchronization as well as use of second services to further differentiate herds and perhaps better identify differences in parameters.