Saturday, September 15, 2007

How do you know when a cow is due to calve?

It's a question I seem to encounter a lot.
Every cow is different, and may not show all the typical signs at the exact same time.

Paperwork helps. Record every observed or artificial mating. Your cow is due to calve 284 days after the last mating (usually) and can be expected to give birth within a week of that date - some go late, some early, probably 90 - 95% calve within five days of their due date.
Note: a heat period when run with the bull is the same as a mating, even if mating is not observed. Note down the date - if she doesn't return to heat on the next cycle, she's probably pregnant.

This is an empty heifer, two years old. There is no udder development, her side is flat and her tummy tucks high against her hind legs. But more notably - she skips and runs everywhere. She ought to be coming on heat every three weeks - she ain't, or she has very short, quiet heats if she does.

Heifers udders don't develop until they are pregnant. About the earliest a heifer is detectably pregnant by looking at her udder is three months along, and some heifers may be later than that before they show. By six months along the udder should be well-developed.
Cows udders begin to fill out between six weeks and two weeks before birthing. The cow pictured below is due to calve in three weeks.

As the cow gets closer to calving, she is laying down colostrum in her udder, which will gradually expand. Her diet has a significant effect on the size of her udder at this stage - an underfed cow may hardly spring at all while an overfed one can approach calving with a hard, swollen udder.
In the last two or three days before calving, the udder will become quite tight and the teats full. The area around her tailhead and vulva will slacken, to the extent that her tailhead appears to sink and the whole area may 'bounce' as she walks.
The cow pictured below will probably calve within twenty-four hours.
In fact, she calved about three hours later

Signs to watch for as calving approaches - dripping milk. Kicking at belly. Circling. Thick yellow mucus discharge. Repeatedly lying down then standing again. Lying down straining.
Any of these usually mean that calving has started or is about to start. A few cows, especially heifers, may drip milk long before calving - but more usually it's a safe sign that calving is imminent. Likewise, a certain amount of vulval discharge is normal in late pregnancy, but once you've seen the cervical plug (which is thick and yellow) it's easy to tell the difference.
Glance at the cow's right side. When the calf moves into position, the bulge often flattens slightly. It won't look like the deep hollow she's left with once the calf's out, but she no longer looks as prenant as she did.
The cow below has started calving, and is in second stage labour.

Use your ears. When approaching a paddock of calving cows - especially in the dark of night - I listen mainly for two sounds; the bellow of a cow in labour and the soft nicker of a cow looking after its calf. Often then, I know before reaching the paddock what to expect and whether all is proceeding well.


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