Maternal plasma oestrone sulphate concentration prior to parturition in relation to birth weight of the calf in primiparous, 2-year-old, Angus heifers

Dystocia and assisted calving in primiparous heifers are persistent problems in beef herds, and incidence increases with increasing birth weight of calves. Plasma samples taken from 33 primiparous, 2-year-old, Angus heifers 2 days prior to parturition were analysed for oestrone sulphate concentration. Additional samples taken at 4, 6, 8 and 10 days prior to parturition were analysed for 17 of these heifers. At parturition, birth weight of the calf, post-partum live weight of the heifer, assistance at calving (n = 6) and status of the calf (stillborn (n = 4) vs. alive) were recorded. Maternal plasma oestrone sulphate concentration was stable from 10 to 4 days prior to parturition and increased between 4 and 2 days prior to parturition for non-assisted heifers. Maternal plasma oestrone sulphate concentration did not affect the probability of assistance at calving or stillbirth.