Non-linear model analysis of categorical traits related to female reproduction efficiency in beef cattle

Abstract

________________________________________________________________________________ AbstractThe utilization of non-linear threshold models and linear animal models to estimate variance components for categorical reproductive traits in beef cattle was investigated. Three traits, retention (RET), stayability (STAY) and calf tempo (CT) were defined. The data set consisted of 36 880 Afrikaner beef cattle measurements recorded over a period of 10 years. After editing, the records of 7 746 females from 473 sires were available for the genetic parameter estimation for RET. The corresponding number of records for STAY and CT were 3 018 (243 sires) and 7 653 (465 sires), respectively. Using GFCAT, sire variances for RET, STAY and CT were estimated as 0.202, 0.072 and 0.114, respectively. With error variances pre-set to one, the heritability estimates on the underlying scale were calculated as 0.67, 0.27 and 0.41 for RET, STAY and CT, respectively. From the three traits analyzed in this study CT probably reflects the true fertility of the bull's female progeny best.________________________________________________________________________________

Genetic parameters for an alternative criterion to improve productive longevity of Nellore cows1

“…A greater estimate of heritability (0.41) was reported by Rust et al (2009), after using a threshold sire model to analyze the trait regarded as calf tempo (CT) in Afrikaner beef cattle. The defi nition of CT was the closest to our definition for NC53, so that records of CT fell into 3 categories depending on whether a cow had 0, 1, or 2 calves before 5 yr of age, given she was weighed at of 18 mo of age.…”