Calving time can be stressful for the cow and the herdsperson. It is one of the most important time points in the lactation of the cow. With that in mind, researchers from Ohio State University conducted a study to determine when assistance should be given during calving. In their literature review they found that the primary causes of dystocia (difficult calvings) were calf/cow size mismatch, calf malpresentation, and dam-related causes such as uterine torsion and hypocalcemia. With first-calf heifers, the most common calving problems seem to be calf/cow size mismatch and narrowing of the birth canal. With mature cows, the common problems included calf malpresentation and maternal-related issues.
Training on calving management has been shown to improve success when dealing with dystocia cases. The training or educational program should include clear recommendations on the signs of calving as the process progresses, when and how it’s appropriate to intervene as well as hygiene.
The objectives of the Ohio study were:
- To assess the time from the appearance of the amniotic sac to the time that the feet appear with or without assistance
- To estimate reference times to be used as guidelines for intervention and assistance.
Researchers characterized the calving process into three stages. Stage 1 (dilation phase) is characterized by cervical dilation and uterine contractions. Behavior changes include smelling the ground, nest building, licking their own bodies, vocalization, discharge of manure, restlessness and tail raising. Stage 2 (expulsion phase) is characterized by the appearance of the amniotic sac outside the vulva, abdominal contractions and the calf progressing through the birth canal. Stage 3 (expulsion of fetal membranes) is characterized by the passage of the afterbirth within the first 24 hours after birth.
Within these stages researchers saw slightly different behaviors between first-calf heifers and more mature cows. During Stage 2, mature cows usually were laying down at the onset of abdominal contractions and remained there until birth. The amniotic sac appeared about 10 minutes after the first set of contractions. In contrast, first-calf heifers showed restless behavior characterized by increased frequency of laying-standing positions at the beginning of labor.
In dystocia cases where intervention was eventually needed, the cow had abdominal contractions for about 95 minutes during labor, compared to 60 minutes for normal births. In dystocia cases, the amniotic sac appeared about 18 minutes after contractions and the feet appeared about 36 minutes later.