Productivity of Hereford, highgrade Simmental and Belmont Red beef herds in central Queensland. 1. Pregnancy, calving and weaning rates

Abstract

Reproductive rates of Hereford, highgrade Simmental and Belmont Red herds, grazing predominantly improved pastures growing on cleared brigalow country in the subtropics, were compared over 4 joining seasons. There were a total of 24 Hereford, 23 highgrade Simmental and 26 Belmont Red single sire joining groups. Three Hereford and 7 highgrade Simmental sire groups which had abnormally low pregnancy rates, were removed from the main analyses. The Belmont Red herd had the highest (P<0.05) pregnancy, calving and weaning rates (87, 85 and 81%, respectively). Hereford and highgrade Simmental herds had similar pregnancy (78 v. 75%) and calving (76 v. 73%) rates, but the Hereford herd had higher (P<0.05) weaning rates (68 v. 60%). Reproductive rates were affected by seasonal conditions, being lowest in the 1982-83 joining year which followed drought conditions. Depression in productivity, due to seasonal conditions, was greater in the Hereford and highgrade Simmental herds than in the Belmont Red herd. Pre-natal foetal losses from established pregnancy to the start of calving averaged 2.5% of pregnant cows, with no breed effect. Peri-natal calf losses, from the start of calving to 7 days post calving, were lowest in Belmont Red (2.9%) and higher in highgrade Simmental (1 0.2%) than Hereford (5.8%) (P<0.05). The incidence of assisted births amongst primiparous 3-year-old cows was Hereford 11.9, highgrade Simmental 21.7 and Belmont Red 2.5% (P<0.05) and averaged 0.4% amongst multiparous cows, with no breed effect. Birth weights of calves that died during the pen-natal period were 37.0, 42.5 and 35.0 kg for Hereford, highgrade Simmental and Belmont Red, respectively, and were 2.0 kg higher than those of calves that survived to weaning. Post-natal calf losses were lower (P<0.05) in the Belmont Red (1.7%) than in the Hereford and highgrade Simmental herds (5.1%). Birth weights of calves which died postnatally were 2.1 kg lower than those of calves that survived to weaning. Death rates of primiparous cows were Belmont Red 2.0, Hereford 5.8 and highgrade Simmental 11.8% (P<0.10). Amongst multiparous cows, death rates were Belmont Red 0.9, Hereford 2.2 and highgrade Simmental2.9% (P>0.05).