Calving season is a time of nervous anticipation. We look forward to the new crop of calves and seeing the past year's efforts hit the ground running. But calving problems (or dystocia) are a concern for many cow–calf producers.
Calving problems happen in 10% to 15% of first-calf heifers and 3% to 5% of mature dams. These difficulties threaten the health of both dam and calf. In addition, difficult calvings cause cows to take longer to breed back, resulting in a longer calving season next year or open cows at pregnancy test time.
The real cause. The factors leading to problems fall into two categories:
abnormal fetal-to-dam-size ratio and abnormal physical presentation.
The birth process relies on an appropriate relationship between the size of the fetus and the birth canal, or pelvis. If the fetus is too large or the pelvis is too small, calving problems will likely ensue. EPDs for birth weight and calving difficulty in some breeds can help producers use genetic selection to prevent calving problems.
Abnormal physical presentation of the calf also causes birthing problems. The normal position for calving is an anterior presentation—both front feet first and the head tucked between the legs. If the calf doesn't present in this manner or twins are present, calving may not proceed normally regardless of calf size.
Know when to give help. The most difficult decision is determining when or if to intervene. Assist too late in the birthing process and the calf, as well as the cow, may perish. Assist too soon and the cow may not be dilated enough to give birth. It's important to understand the normal birthing process before intervening.
Precalving cows develop their mammary glands, or "bag up," two to three weeks before delivery. As the dam nears calving, the ligaments in the pelvis relax, giving the vulva a fluctuation when the dam walks that is often referred to as "springing." You may also notice a mucus plug several days before calving. These changes lead to the beginning of the birthing process, which can be broken into three stages:
Stage One. Mild uterine contractions progress to dilatation of the cervix. The cervix is a cartilage and muscular ring that controls communication between the uterus and the outside world. It is closed during pregnancy to keep harmful environmental elements out, but must fully dilate to allow the calf to pass through. Cows in this stage are often restless, not likely to eat, and may isolate themselves from the herd. Some may act uncomfortable or colicky. During this stage, uterine contractions push the calf toward the birth canal.
The conclusion of this stage is the rupture of the placenta and discharge of amber-colored fetal fluids—in other words, the cow's water breaks. Stage One lasts 1 to 12 hours, with 1 to 4 hours being most common. If fetal membranes (the water sac) are exposed with no further progress in 2 to 3 hours, intervention should be considered.
Stage Two. As the calf enters the birth canal, it stimulates strong abdominal straining. The cow often lies down during this stage and uses her full force to push the fetus into and through the birth canal. For a calf in normal presentation, the front feet are the first to exit the birth canal, with the bottom of the hooves facing down. If the head or tail is exposed prior to the feet or the feet appear to be upside down, immediate assistance is needed. Progress is the most important thing to observe during this stage; once the cow starts pushing the calf through the birth canal, she should make consistent advancement toward expulsion of the fetus.
Once hard straining begins, the feet of the calf should be visible within 30 to 60 minutes. If no part of the calf is visible after an hour, consider stepping in. Watch cows in this stage closely. With breech calves (backwards calves that present the tail and hips instead of the front feet), the dam may not strain or may quit straining due to a lack of progress. Evaluate cows to determine if straining stopped because she is still in Stage One or if she is in Stage Two and needs assistance to deliver the calf.
- January 2010