BeefTalk: May Calving Bull Turnout is Aug. 1
By Kris Ringwall, Beef Specialist
Given later calving, 99 percent of the cows are calving within the first two
breeding cycles (42 days) at the Dickinson Research Extension Center. The center
switched to May calving in 2012. So far, following late-calving on grass in 2013
and 2014, the cows have rebred very well. Again this year, the bulls will be
turned out on Aug. 1, with the expected start of the 2015 calving season set at
The actual first full-term, live calf was born on April 28 in 2013 and April 27
in 2014. The projected calving date is from a calving gestation table that uses
283 days as an average length of a cow's pregnancy. Obviously not all cows have
a gestation length of 283 days. Those first- calving cows are wrapping up
pregnancy at about 270 days and delivering healthy, although smaller birth
When the center summarizes the calving data, May 31 will be considered the end
of the first 21 days of the calving season and June 21 will be considered the
end of the first 42 days of the calving season. Given the current success, the
center will be done calving by mid-June, with a projected 80-plus percent of the
calves born in May.
How does this compare with typical values for those herds that calve earlier in
the spring? The center is 11 percent ahead of the numbers.
In the production world, the North Dakota Beef Cattle Improvement Association
has utilized the CHAPS program through the North Dakota State University
Extension Service to evaluate cow-calf production values.
If we were to compare the reproductive values of the center's current production
against the standard benchmark data, the reproduction rate is excellent. The
CHAPS benchmark for the number of calves born within the first 21 days is 63
percent, while the number of calves born within 42 days from the start of the
calving season is 88 percent.
The benchmarks are presented yearly as composite five-year rolling values and
provide the industry with some typical values to evaluate against an individual
So why the success? At least for the last two years, the cows have not had any
issues with cycling and the bulls certainly have been fertile in August.
However, the system is not perfect.
Last year, the center had a bull that went unsound during breeding. It was
noticeable in the final total herd reproductive numbers. After evaluating the
ultrasound results for pregnancy last fall, the two original bulls only
conceived seven pregnancies the first 21 days of the breeding season. During the
second 21 days of the breeding season, prior to replacing the injured bull, 13
conceived in 13 days. When the replacement bull was added, 15 cows conceived in
This points out the need for a reasonable observation time during the breeding
season, regardless of when one breeds. The other potentially weak link is the
replacement heifers. In 2012 and 2013, the center bred May- and June-born
heifers. These heifers would be the same age that more traditional early calving
producers would be breeding in June.
The open rate seems to be greater when breeding May- and June-born heifers in
August. Is that a concern? We will wait another year to see what happens. The
center neuters (spays) all the extra heifers, and any replacement heifers that
are open in October are spayed and included in the feedlot shipment.
All the spayed heifers did well, regardless of being spayed in the spring or
fall. This means that keeping extra heifers in the breeding pasture is not an
issue, and natural selection will help assure that only fertile heifers actually
are retained in the herd. From a management perspective, an early pregnancy
diagnose is very critical in the heifer pasture, as is keeping all marketing
options open. Again, this would be true regardless of when a producer calves.
In fact, those producers who bred heifers in late May and early June should be
checking with their local veterinarian and could plan on pregnancy checking
those heifers as early as mid-August.
The other issue that seems perpetual for late-calving producers is the challenge
of keeping the neighbors' bulls out of the cow herd. Most traditional calving
producers will have their own cows pretty well bred by mid-July, which leaves a
lot of fertile bulls with nothing to do.
The right wind and a pasture full of open cows just down the road is a
temptation a lot of bulls will not turn down. With some very determined fence
crawling, bulls will get around the neighborhood more than is desired, so a
watchful eye is needed and much appreciated during May calving.
May you find all your ear tags