Parturition, or the birthing process, has three stages. Understanding the stages is critical to know when to provide assistance.
Kansas cow-calf producer Debby Lyons-Blythe shares on her “Kids, Cows and Grass” blog a step-by-step explanation of how a cow calves. Although her blog’s target audience is non-ag folks, it is a great reminder for anyone in the beef industry.
According to AJ Tarpoff, Kansas State University Extension veterinarian, the stages of parturition, or calving, are divided into three main phases.
Stage 1: Initiation of Labor and Appearance of the Water Bag
This stage involves hormonal changes and physical preparations for calving, including the start of uterine contractions, relaxation of muscles and the cow showing behavioral changes. You may notice switching of the tail and a thick clear mucus string hanging from the vagina. A cow’s appetite may decrease, and it may separate themselves off from the herd.
“Stage 1 ends when we get loosening and dilation of the cervix, the first fetal membranes get pushed through the birth canal, and what we see on the outside is the water bag,” Tarpoff says. “That’s what everybody talks about it, but it’s the first fetal membranes that come through.”
This stage may take hours or days to complete and can easily go unnoticed.
“If you see an animal acting a little bit uncomfortable in the morning ... we give her a few hours with close observation, and we look for the water bag,” he adds. “Once that water bag breaks, however, that’s when we start our time.”
Stage 2: Delivery of the Calf
This is the action stage when the cow pushes and the calf is born. Contractions are strong and coordinated. This stage officially begins with the appearance of the water bag at the vulva. This is the time to start your clock.
“Once that water bag breaks, it’s the rule of an hour, and that’s an hour that they should make adequate progress through the birthing process, because once that water bag breaks, that’s the beginning of Stage 2 of calving,” Tarpoff explains.
“During Stage 2, she’ll have a high tail, she’ll hold her breath ... the true delivery portion of the process,” he adds. “Once that water bag breaks, after an hour, if it’s a mature cow and there’s no calf, then we would intervene.”
In heifers, not only is the pelvic opening smaller, but the soft tissue has never been expanded prior to that first birth. Older cows have had deliveries before and birth often proceeds quite rapidly unless there is some abnormality such as a very large calf, backward calf or twin birth.
Stage 3: Expulsion of the Placenta
After the calf is delivered, the cow’s body must expel the placenta, commonly referred to as afterbirth. If retained, do not forcibly remove it.
“The third stage is passing of the placenta,” Tarpoff explains. “The uterus continues to contract after birth, and that helps with the process of detachment. It can normally take up to 12, even 24, hours for that placenta to pass. It’s after that time that it may be a concern. That’s when I highly recommend working with your local veterinarian.”
When Is It Time to Intervene?
Tarpoff says offering assistance is a matter of judgment, and good judgment is the result of experience.
He reminds producers to remember the “rule of an hour”: Intervene if a mature cow hasn’t made progress within one hour of the water bag breaking. For heifers, the process can take a bit longer.
If you don’t know when Stage 2 began and the process seems to be slow, it may warrant a vaginal exam.
For more tips regarding intervention timing, see Tip 6 in: 9 Tips to Ensure Calving Season Success
When Is It Time To Call for Help?
Tarpoff says don’t hesitate to seek veterinary help when needed for complicated or high-risk situations.
It is important to understand when to call for extra help or veterinary support. Visual red flags to intervene immediately include: head-only presentation, head with only one leg, and backward calf with hocks visible but not progressing.
Tarpoff stresses when intervention becomes necessary, safety and assessment come first.
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