An investigation on the effect of management factors and contemporary group definition on the genetic evaluation of Calving Interval in British Limousin cattle

Abstract

Female fertility is an important component of a beef production system. In the British Limousin genetic evaluation there are several female fertility traits recorded (Coffey et al. 2007). Two of these traits are calving interval (CI) and age at first calf (AFC). In British beef breeds, Roughsedge et al. (2005) estimated moderate negative genetic correlations between CI and AFC; early maturing animals (low AFC) had longer CI because of genetic factors. However, it has also been suggested that management factors could be increasing the CI EBV of early maturing animals. For example, does the CI EBV account for heifer’s that calve early for the first calf, but then are not given the opportunity to re-mate when they first return to oestrus, and therefore, may have a longer raw CI record. There were two aims of this was work 1) to investigate if CI EBVs produced by the British Limousin genetic evaluation were affected by management decisions applied to early maturing animals (i.e. low AFC) and 2) to assess if reducing the season slice (i.e. reducing the chance of directly comparing early and late calvers) for the CI contemporary group (CG) improved the CI model.