Cows, much like humans, experience a nine-month pregnancy.
Just as overdue pregnancies can cause discomfort and complications in women, the same can happen in cows.
Choosing shorter pregnancy durations in the breeding and herd management procedures can assist cattle farmers in achieving a herd that is healthier, more efficient, and ultimately more profitable.
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Optimizing Cow Pregnancy Duration for Healthier Herds
The average gestation length for a cow is 283 days. However, several factors can affect that.
Some breeds are known to have longer gestations.
Holsteins have the shortest average gestation at 279 days in dairy breeds, while Brown Swiss, a rare heritage breed, goes the longest at 291 days. Angus cows are the quickest to calve in beef cattle, with an average 283 gestation, while Blond d’Aquitaine cows, a large French breed, go more than a week longer, at 294 days.
Unfreshened heifers tend to have their first calf a few days earlier than mature cows that have calved before. And bull calves tend to “cook” a little longer, gestating for potentially several days longer than heifer calves. Also, calves born in the fall calving season, birthing sometime between August and October, tend to arrive faster than calves born in the spring —January through March — calving season.
But, the most significant factor that affects gestation length is the genetics of both the dam and the sire.
Selecting for Smaller Calves Equals Shorter Gestation Lengths leads to a healthier herd
When cattle producers started breeding their cows to bulls know to throw calves with lower birth sizes, they realized that those bulls also tended to sire calves with shorter gestation lengths.
Smaller calves equal easier calving. That avoids a cow needing birthing help from human hands and can dramatically affect how quickly a cow recovers from birthing and can be bred back for her next calf, increasing the herd profitability over the long term.
Towards the end of a gestation period, the unborn calf gains one to one and a half pounds each day. So, a cow that goes a week longer can easily have a calf 10 pounds heavier than it would have been and run into trouble when the birthing process begins.
Using bulls that throw smaller calves and shorter gestation periods is one strategy producers often take, but the dam’s genetics are also at play. If the dam typically gestates for a shorter period and that cow is bred to a bull that throws smaller calves (aka has a shorter gestation length), she will almost always have a short gestation (and smaller calf). However, if the dam tends to go longer in her gestation cycle but is bred to a sire known for siring calves with a shorter gestation length, it will be a toss-up.
A wise producer will carefully record their cow’s gestation records throughout their calving history, no matter who they are bred to. Replacement heifers should ideally be selected from dams that reliably have shorter gestation lengths.
Signs Calving is Imminent
Even with good records and history on the pregnant cow (and the bull she was bred to), cows and heifers can beat their own drummer when it comes to their calving time.
Knowing what signs to watch for predictive of imminent calving can help a producer prepare for a birthing cow in distress. Or be on the lookout for a newborn calf that may need help.
One of the most obvious signs is the development of the udder, though, for some cows, that can begin are early as six weeks before calving, while other cows will fill up during their last days of gestation. Or even overnight, producing a calf in the morning!
Experienced producers look for the teats to start filling. Even if they have been “bagged up” for several days, the teats typically won’t become full until the cow is ready to calve. The cow may even start leaking a bit as the birthing time approaches.
Cows may also produce a mucus discharge, even a long string of mucus, from the vulva when the cervical plug softens and is pushed out. Another sign is the vulva enlarges and the tissue becomes soft and distended. But again, some cows may show this sign many days before birthing, while others do it only hours before.
Many producers swear by feeling the pelvic ligaments to predict calving. The ligaments between the cow’s tail head and the pin bone on either side usually appear very hard and tight. However, a few hours before labor, they will start to become loose and appear sunken. A soft, loose pelvic ligament — the cow has to be standing for the producer to inspect adequately — typically means a calf within 12 hours.
We hope this information was helpful in your cattle production!