Sadly one of our 2015 born sable heifers lost her first-born calf earlier this month due to the fact that the calf was too big to give natural birth. This was however a great learning experience for the breeding camp staff as Dr Louis Greeff explained to them what the signs and symptoms are to look out for when a cow is giving birth and to identify complications before it is too late to save the calf.
There are three stages of labor in normal calving:
First stage: The first stage of labor is when the cervix is dilating. This stage can last between 1 and 24 hours, but usually it is between 2 to 6 hours. Cows will often separate from the herd, and may be restless. They will not eat or drink and can have a vaginal discharge.
Second stage: The second stage begins when the cow starts contracting and continues until the calf is delivered. The amniotic sac, or water bag, will appear at the vulva. The fetus starts to enter the birth canal which then stimulates contractions that can be seen as abdominal press. A general rule is that delivery should be complete within 2 hours after the amniotic sac appears.
Third stage: The third stage is when the placenta (afterbirth) is delivered. The placenta usually passes within the first 8 hours after birth. It is considered “retained” at 12 to 24 hours, but manually removing the afterbirth is not recommended.
Dystocia is when it becomes difficult or impossible for the cow to deliver the calf without assistance. It can occur in the first and/or second stage of labor. Producers may not know the exact time the cow goes into labor, but careful observation, and knowing the general guidelines will help identify dystocias early.
Causes of DYSTOCIA
The most common causes of dystocia are maternal/fetal disproportion, abnormal position of the calf during delivery, incomplete dilation of the cervix, uterine inertia (the uterus will not contract, or becomes “exhausted”), uterine torsion, twins, and abnormal fetuses.
The most significant cause of dystocia is maternal/fetal disproportion. This is a condition when the calf is too large for the female to deliver without difficulty. Heifers are at the greatest risk of maternal/fetal disproportion. Current recommendations to maximize profitability and decrease dystocias are to calve heifers at 24 months of age. Calving heifers at 24 months of age minimizes the feeding expenses associated with developing heifers while keeping the heifers calving during the same calving season as the mature cows. Well-managed and properly grown heifers will only be 85 percent to 90 percent of mature cow size at 24 months of age and not have as much room in their pelvis (birth canal) as do mature cows; however, underdeveloped heifers may only be 60 percent the size of mature cows and are at much greater risk of dystocia.
Improper nutrition may not only result in heifers being too small at breeding, but also may compromise the amount of energy available for labor. Undernourished heifers are more likely to become exhausted and have prolonged deliveries. In contrast, heifers that are too fat may have difficulty delivering calves because of the excess fat in the birth canal.
As genetics became better understood, it is apparent that there is a link between birth weight and calf growth. Calves that have higher growth potential also have higher birth weights. Another important factor that was discovered is that the bull primarily determines the birth weight of the calf. The industry also found that by breeding for more growth in their calves, they were also creating many more dystocias.
The big question is: when is a delivery a dystocia rather than a normal birth? If the amniotic sac appears at the vulva, then a good rule of thumb is the calf should be born within 2 hours. For a mature cow, it will probably be closer to 1 hour. If you do not know when the animal began labor, the most reliable way to assess if the animal is having trouble is the progress it is making.
A cow or heifer should be making visible progress every 20 to 30 minutes that she is in active second-stage labor. One that frequently tries to urinate or walks with her tail up and extended for more than 3 to 4 hours may have a uterine torsion (twisted uterus), an abnormally positioned calf, or other condition that blocks passage of the fetus and membranes so they are not visible.
If there is an extended second-stage labor or the animal is not making progress or frequently assumes a urinating posture over several hours, it needs to be examined. When examining a cow, good sanitation is very important future reproductive problems. You will need proper restraint for the animal that should include access to a chute and headgate. Clean the vulva with a mild soap and water and wear plastic OB sleeves to protect both the cow and you from infectious agents. The vulva should be relaxed and free of obstructions like fat and pelvic fractures, and the cervix should also be relaxed and dilated large enough for the calf to pass through. When you pass your hand along the birth canal, there should not be any band marking the border between the birth canal and uterus, that is, you cannot identify the cervix. Next, determine the position and size of the calf.
The normal position for a calf during delivery is both front legs extended with the head following and facing forward in a “diving” position (See Figure 1). If the cow is dilated and the calf is in the normal position, but still no progress is being made, maternal/fetal disproportion is likely. Never attempt to deliver a calf in an abnormal position without first correcting its presentation as you could cause irreparable damage to the cow. Call a veterinarian if there is any question regarding the presentation of the calf or as soon as you have exceeded your ability or comfort level.
Figure 1. Calf in the correct position for a normal delivery.
Because many of the causes of dystocia, such as abnormal calf position and uterine torsion, are sporadic and unpredictable, prevention focuses primarily on correcting fetal/maternal disproportion and nutrition.