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.
Study results demonstrated that cows with assisted births (dystocia) had a longer period from the amniotic sac appearance or feet appearance to birth and increased incidence of stillbirths compared with cows with unassisted calving. Although not significant, the researchers say it is important to note that the time spent in labor varied for first-lactation animals and cows with multiple lactations.
This study suggested that calving personnel should start assisting cows 70 minutes after amniotic sac appearance (or 65 minutes after feet appearance) outside the vulva (based on births without assistance). Under field conditions, the observation of amniotic sac or feet appearance as calving progresses are clear and concrete landmarks that calving personnel can easily identify. Early intervention has the potential to prevent stillbirths, but also has the potential for dam injury due to lack of proper dilation of soft tissues.
When a calf malpresentation is evident (like the appearance of one foot outside the vulva) immediately after amniotic sac appearance, or for uterine torsions (where the amniotic sac or feet do not appear outside the vulva), obstetric intervention is rendered. The time spent in labor (straining) combined with the time from the amniotic sac or feet appearance to birth and the assessment of calving progress (as described for non-assisted births) should be used as guidelines to determine the appropriate time for intervention during difficult births under field conditions. Keep in mind, these reference times should be interpreted in combination with adequate obstetrical knowledge and examination.
To learn more about when and how to assist with calving, plan to attend the Carver County/University of Minnesota Dairy Expo on Monday, February 18, 2013 in Norwood Young America. At that conference, Dr. John Zimmerman will be discussing and demonstrating how to deal with calving conundrums. To view a complete program brochure online, go to http://z.umn.edu/dairyexpo.
Source: Laura Kieser, Extension Educator, University of Minnesota Extension, Scott and Carver Counties