Dr. Les Anderson, Extension Beef Specialist, University of Kentucky

Maintaining a controlled breeding and calving season can be one of the most important management tools for cow-calf producers. A uniform, heavier, and more valuable calf crop is one key reason for keeping the breeding season short. Plus, more efficient cow supplementation and cow herd health programs are products of a short breeding season. However, converting from a year-long breeding season to a shortened 2 to 3 month breeding season should not be done haphazardly.

A system for converting from year-round to a 75-day controlled calving season over a period of two years would present less loss and fewer problems than to try to convert in one year. The following steps are suggested for getting on a controlled breeding system:

1. Determine the ideal time of year and the length of your new calving season. For example, my cows will calve from February 15th to April 30th (74 days).
2. Determine the reproductive status of each cow in your herd. First, go to your record book to determine the last date each cow calved. If you don’t keep records, try to match the cows and calves up and estimate their age. For example, let’s assume we have 30 cows. Calving dates from fall 2014 to spring 2015 are as follows: Last Aug 2014 = 0 cows calved, Sept = 2 calved, Oct = 2 calved, Nov = 1 calved, Dec = 0 calved, Jan = 0 calved, Feb = 3 calved, Mar = 9 calved, Apr = 5 calved, May = 5 calved, June = 2 calved, July = 1 just calved. Keep in mind that the 5 cows that calved in the fall are likely pregnant.
3. Based upon the reproductive status of your herd, determine if you would like one controlled calving season or two. In our example, 5 cows calving in the fall are likely not worth the hassle so they will be held over and should NOT be exposed to a bull until next spring. If, however, half of your herd calved July-December, it is a better economic decision to make these your fall-calving cows and the ones that calve from January-June your spring-calving cows.
4. Build a good strong bull pen or well-fenced bull pasture. An electric fence in addition to the regular fence may be needed.
5. Remove your bull(s) from the herd. Select the removal date to coincide with about a 120 day season for your spring-calving cows. In our example, we would remove the bull(s) near the end of August. He would stay in the bull pen until May 7th of next year.
6. Sixty days after removing the bulls from the herd (or at a convenient time near this date), pregnancy check all cows and cull all non-pregnant dry, breeding-age females that have been running with the bull and all non-pregnant cows with calves 5 months of age or older. Your fall-calving cows have likely either calved or are very close to calving.
7. You may want to consider starting the breeding season of your replacement heifers 20 to 30 days ahead of the final breeding date for your herd. Most extended calving seasons are the result of failure of young cows to rebreed in a timely fashion. The additional 20-30 days enhances the opportunity for these young cows to rebreed next season. So, your replacement heifer breeding season would start around April 10th and these females would begin calving around January 20th. I realize that this is a bit early for calving and you might experience 1-2% higher calf death loss. Financially, 1-2% death loss is easier to swallow than a 25% decrease in pregnancy rate the following year.
8. The second year, follow the same system as outlined about except remove the bull on the week of July 20th. If you have fall and spring calvers, then put the bull in for the fall cows around November 20th and remove him around January 20th.