Summary and Implications
The purpose of this study was to investigate the feasibility of using a linear random regression model for the analysis of female fertility as expressed by days open. The analysis provided insight about the kind and amount of variation over the trajectory for age at calving from 24 to 72 mo. Correlations between permanent environmental effects changed from positive to negative values with greater distance between days open in young cows and days open in older cows; r(24,36)=0.88, r(24,72)=-.65. The random regression animal model proved to be a better alternative to a repeatability animal model for prediction of breeding values for days open. Random regression enables breeders to pick the optimum age at calving to select female replacements with enhanced fertility or fewer days open per lactation. Further research is needed to evaluate the advantages of using random regression model on the genetic analysis of days open.
Iowa State University
Gutierrez, Gustavo A.; Healey, Mary H.; and Berger, P. Jeff
"Genetic Analyses of Days Open Using a Random
Regression Model ,"
Animal Industry Report:
AS 654, ASL R2304.
Available at: http://lib.dr.iastate.edu/ans_air/vol654/iss1/53