Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Animal, Dairy, and Veterinary Sciences

Department name when degree awarded

Animal Science

Committee Chair(s)

James A. Bennett


James A. Bennett


Paul R. Grimshaw


Donald V. Sisson


Causative factors and some consequences of dystocia were examined in 3923 parturitions among Hereford and Angus x Hereford crossbred two-year-old heifers. Fifty percent of the parturitions required some assistance. Minor assistance was required in 34.5% of the parturitions and major assistance involving use of a calf puller, in 15.1%. Caesarean section and foetotomy were rendered in 0.3% and .05% of the cases, respectively. Abnormal presentation at birth, which included leg back, head back, backwards, hiplock and breech, was observed in only 2.9% of the births and therefore is a minor contributor to dystocia. The major causes of dystocia were not specifically identified in this study. Sex of calf had a definite influence upon the degree of calving difficulty with male calves requiring more assistance in both minor and major assistance categories. Crossbred heifers had a higher percentage of unassisted births (62.4% vs 36.7%) than Hereford heifers. Ninety and eight-tenths percent of all calves born were alive at 30 days postpartum. Of the 9.2% that died, 6.2% died at birth or within 24 hours after birth. Losses were particularly heavy in this early period among those to whom major assistance had been given, with 71.5% of all deaths in this group being in this early period. Death loss rate was higher in this group throughout the 30 day postpartum interval with a total death loss of 38.6% as compared to a loss of 3.8% and 3.4% for the minor assisted and the unassisted groups, respectively. Among the kinds of abnormal presentations, death loss was greatest among breech presentations with a 66.7% loss. Backward presentation ranked next followed, in order, by head back, hiplock and leg back. Loss from leg back, 21% was relatively low. Increases in degree of severity of dystocia was accompanied by increases in time required to complete the birth process. Labor duration and sex of calf were correlated with male calves requiring a longer parturition than female calves, 104 minutes vs 88 minutes, respectively.