Birth Weight EBVs are estimates of genetic differences between animals in calf birth weight. Calf birth weight is the biggest genetic contributing factor causing calving difficulty in heifers.
Birth Weight EBVs are expressed in kilograms (kgs) and are calculated based on weights of calves taken at birth. Small, or moderate, Birth Weight EBVs are more favourable. For example, a bull with a Birth Weight EBV of +2 kg would be expected to produce lighter calves at birth than a bull with a Birth Weight EBV of +6 kg, with a lower risk of a difficult birth.
Please note, whilst low Birth Weight EBVs are favoured for calving ease they are also generally associated with lower overall growth potential. Consequently, birth weight and growth need to be carefully balanced. Fortunately, animals can be found that have both moderate Birth Weight EBVs and above average EBVs for later growth.