Milk and weight EBVS are associated with cow and calf gain during lactation but carcass EBVS are not

Abstract

In a series of in-depth interviews with seed-stock producers in southern Australia many breeders spoke about the importance of the ability of cows to gain energy reserves post-calving within their on-farm management system. Moreover, several breeders believed maternal, carcass and weight EBVs to influence a cow’s ability to gain weight and energy reserves during lactation. This paper reports on heritability of cow weight change and body composition change traits during lactation, calf weaning weight (CalfWt), and total Cow+calf weight gain from calving to weaning for Angus cows. In addition, significant regressions of cow change traits, CalfWt and Cow+calf weight gain on current Breedplan EBVs are reported. Heritability estimates for CalfWt, cow weight change, rib fat depth change and eye muscle area (EMA) change during lactation and Cow+calf weight gain were low, ranging from 0.07 to 0.13. Cow EBVs with significant effect on CalfWt were 200 day weight (Wt200) (0.38±0.09kg/kg EBV) and 200 day maternal (MILK) EBV (1.00±0.15kg/kg EBV). Increased mature cow weight (MCWt) EBV was associated with greater gain in cow weight and rib fat depth during lactation whilst increased MILK EBV was associated with cow weight, rib fat and EMA loss during lactation. MILK EBV was not associated with the combined weight gain of the Cow+calf during lactation. Rib and EMA EBVs of the cow were not associated with CalfWt, change in cow weight, rib fat or EMA during lactation, or Cow+calf weight gain.