That Cow Wasn’t Supposed to Calve Today

For most beef producers, the final days of the last
trimester of pregnancy for their cow herd is here. For
some early bird producers, calves are already bucking
and jumping. Winters like this one are great (keep your
fingers crossed) and temporarily lay to rest all the
discussion of when to calve.
Often, producers question when a particular cow is
due. Most producers have a handy calving table that
projects the calving date of the cow based on the day
she was bred. For example. the IRM Pocket Reference
guide shows a cow bred May 21 is due to calve on
March 1.
In recent years, the North Dakota State University
Dickinson Research Extension Center has targeted
March 1 as the start of the calving season. Do the cows
begin calving on March 1? Unfortunately, the cows do
not read the tables. Basically, a cow will calve when she
and her calf decide the time is right.
We have all seen the old cow that gets up, lays
down, gets up, lays down, walks over to the corner,
walks back, lays down, twitches her tail and calves two
weeks later. Or the cow with no udder that calves in
what seems to be minutes and successfully produces a
normal, well fed day-old calf.
A current trend is to advertise cows for sale with
predicted calving dates. These dates were projected
based on ultrasound measurements and are used to imply
the cows or heifers should calf over a period of seven to
10 days. Establishing the age of a developing fetus with
ultrasound is very accurate but gestational age and
calving date have little in common.
At the center, ultrasound records help us sort cows
based on 21 day reproductive cycles. No attempt is
made to actually guess which day a cow is going to calf.
In reviewing cow records, center research specialist
Keith Helmuth compiled all the cows with absolute
breeding dates and sire of calf. In other words, 462 cows
were artificially inseminated, and conceived to the unit of
semen she was inseminated with. Because of the
different breeds used, the parentage of the calf is not
questionable. No DNA test or judge was needed to
identify the father.
Of these 462 cows, the average gestation length was
282.5 days. Of the 426 cows, only 87 actually calved on
the expected date. These cows were expected to calf
283 days after breeding or March 1st. In reality, the first
live calf arrived Feb. 11, then one on the 13th and one on
the 16th. Three calves arrived on Feb. 17, three on the
19th, one on the 20th, three on the 21st, nine on the 22nd,
eight on the 23rd and a rush on the 24th produced 17
The calving crew is starting to sweat. On the 25th,
19 calves were born, 36 on the 26th, 38 on the 27th, 39
on the 28th and finally the due date, March 1, 87 calves
were born. More sweat, despite the cold weather. On
March 2, 53 cows calve, on the 3rd, 25 calves, on the
4th, 16 calves, on the 5th, 22 calves, on the 6th, 20
calves, on the 7th, 15 calves, and on the 8th, only four
calves. Just as there appeared to be a let up, on the 9th,
15 calves were born, on the 10th, 12 calves, and on the
11th, one calf. Finally, a slow down and the season
finished with two calves on the 12th, three calves on the
13th, four calves on the 14th, and one calve each on the
15th, 16th and 17th. The last two calves were born on
the 19th of March.
All 462 cows conceived on the same day, but the
calving season lasted 32 days. Approximately, 80 percent
calved within a 11 day window, 95 percent in a 19 day
window and 98 percent within a 28 day window. If you
want to bet me you know when your cow is going to
calf, I will bet you she won’t calf on the day she is due.
Cows don’t calve in a 7 to 10 day window, no matter
who thinks they should.
Happy calving. May you find all your ear tags.
Your comments are always welcome at For more information, contact the
North Dakota Beef Cattle Improvement Association,
1133 State Avenue, Dickinson, ND 58601 or go to on the Internet. In
correspondence about this column, refer to BT0078.

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