Effect of calving process on the outcomes of delivery and postpartum health of dairy cows with unassisted and assisted calvings.

Welfare aspects of obstetrical assistance were studied in multiparous Holstein-Friesian cows (n=176) with (1) unassisted calving in an individual pen (UCIP; n=42), (2) unassisted calving in a group pen (UCG; n=48), (3) assisted calving with appropriately timed obstetrical assistance (ACAP; n=50), and (4) assisted calving with inappropriately timed (premature) obstetrical assistance (ACIN; n=36). Duration of the stages of calving, the prevalence and the degree of dystocia, stillbirth ratio, newborn calf vitality, and the occurrence of postpartum health problems (i.e., retained placenta and vulvovaginal laceration) were recorded. The time from amniotic sac and hooves appearance to birth and the total duration of calving (from the onset of calving restlessness to delivery) were shorter for UCG cows than for any other groups. The overall incidence of dystocia was 31.3% in the calvings studied. The prevalence of dystocia was below 10% in cases of unassisted calvings. The proportion of severe dystocia was higher in ACIN cows than in ACAP cows (47.2 vs. 12.0%, respectively). The prevalence of stillbirths was the highest in ACIN calvings (22.2%), followed by ACAP, UCI, and UCG cows (8.0, 4.8, and 0.0%, respectively). The ACIN calves had lower vitality scores than calves born from ACAP, UCG, and UCIP dams immediately after delivery and 24h after birth. Although ACAP calves had lower vitality scores than UCG and UCIP calves at birth, a delayed recovery of vitality was mirrored by satisfactory vitality scores 24h after birth. Retained placenta and vulvovaginal laceration occurred more often with assisted dams (i.e., ACAP and ACIN animals) compared with UCIP cows with the highest prevalence in ACIN cows. In UCG cows, no injuries occurred in the vulva or vagina, and we noted only 4 cases of retained placenta (8.3%), proportions lower than in cows with unassisted calving in the maternity pen. Our results suggest that calving in a group might have benefits over calving in an individual pen in terms of calving ease, duration of the delivery process, and postpartum health of the dam vitality of her offspring. Premature obstetrical assistance leads to a high prevalence of dystocia, impairs postpartum health of the dam, and poses a potential risk to calf survival.