Dystocia is defined as delayed or difficult parturition. General causes are fetal-maternal size mis-match, fetal malpresentation and maternal-related causes. Meyers et al reported that 50% of still-births were a direct result of dystocia. A slight calving problem increased the odds of stillbirth by 2.91 in heifers and 4.67 in multi-parous cows. More difficult calvings caused a stillborn in heifers to be 6.76 times more likely and 11.36 times more likely in multiparous cows. In 1996, Wells et al reported that a dystocia requiring forced extraction, compared with unassisted calving, was 4.22 times more likely to result in heifer-calf death within the first 21 days of life.
Frank Garry, DVM, MS, Colorado State University, says physiological effects of dystocia on the calf include postnatal metabolic and respiratory acidosis, hypoxemia, failure of passive transfer and hypothermia, all of which can be immediately fatal or reduce long-term sur-vival. “Severe dystocia has been associated with reduced body temperature, decreased concentra-tions of blood cortisol and increased blood glucose,” Garry explains. “Hypoxic calves are often weak and slow to stand and suckle, and this negatively affects absorption of colostral immunoglobulins.”
Dystocia by the numbers
Jason Lombard, DVM, MS and Garry completed a dystocia study (Journal of Dairy Science, 2007) and found over 35% of calves required assistance during birthing, accounting for 75.5% of stillborn calves. Only 10.8% of calves had severe dystocia, but they accounted for 49.1% of all stillbirths. Dys-tocias were scored with 1 = no assistance, 2 = slight problem and 3+ = needed assistance.
“The odds of a heifer calf having any morbidity event were significantly increased for dystocia scores 2 and 3,” Garry says. “The odds of having a respiratory event were significantly increased for dystocia scores 2 and 3.” The odds of a digestive event increased for those with mild or severe dys-tocia. Calves born to cows having a severe dystocia had an increased risk of death after 24 hours of age than calves born unassisted.
Calves having mild dystocia were less likely to survive to 30 days than calves born unassisted. “Se-vere dystocia affects calf survival even more negatively beyond the first 24 hours of life,” Garry notes.
Garry says veterinarians can play a part in helping their clients perform the three steps to minimizing the impact of dystocia. Those steps are:
1. Decrease its occurrence. “This is a complex management issue and not easy to accomplish,” he says.
2. Decrease the impact of dystocia by good calving management practices. “This requires employee training and can be very effective in decreasing the negative impact of dystocia on dam and new-born.”
3. Increase the level and quality of newborn calf care. “This also requires employee training and can help compromised calves to survive and thrive.”