May calving bull turnout is Aug. 1
NDSU Extension Beef Specialist
Again this year, the bulls will be turned out on Aug. 1, with the expected start of the 2015 calving season set at May 10.
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 May 10.
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 weight calves.
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 producer’s operation.
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 eight days.
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.