Studies on Performance Testing for Growth Rate of Dual Purpose Bulls

Abstract

Abstract Adjustment factors considered to be of importance in the evaluation of daily gain of performance tested bulls of the Swedish dual-purpose breeds were investigated. The use of extrapolated growth rate records to estimate daily gain on test was also studied. To investigate adjustment factors, growth rate data was used from the performance testing of bulls born between 1969 and 1974. Adjustment factors were obtained for the influence of month of birth on daily gain and for the effect of breed at the multi-breed test stations. Either multiplicative or additive adjustment factors could be used for month of birth, while additive factors were suggested for the influence of breed. The application of these adjustment factors to bulls born between 1977 and 1982 was only partly successful, as some variation still remained due to the effects adjusted for. It was concluded that the most efficient solution would be to combine pre-adjustment of data with the application of a Mixed Model procedure. The use of extrapolated growth rate records to estimate daily gain on test was studied on 1 412 bulls of SRB and SLB breeds. Daily gain up to one year of age could be estimated with sufficient accuracy by linear extension of the observed growth rate between 6 and 9 months of age.