Heat Synchronizing Heifers

By Judy Brener
from The BueLingo World – Jan-Mar 1993

Since starting our BueLingo herd, we have tried to have our yearlings calve as a group a month before the rest of our cows. We have found that many two-year old cows have trouble conceiving a second calf. We hope to give them more time to recover before breeding them again, and by keeping them separate, they can be watched more closely. We are trying to accomplish this by using heat synchronization and AI breeding. Other advantages include a more uniform calf crop because their ages are closer together and a lessened workload because of a shorter season. Because we use AI we can increase our herd’s blood-lines and match cow/bull traits. We have found that dairy cow heat synchronization techniques and heat detection patches were not 100% reliable with beef cows.

For the 1991 breeding season we tried heat synchronizing twenty heifers using two prostaglandin injections eleven days apart and a heat detector patch. The medication costs and the patch came to about$1 1/head. Out of the twenty, we detected heat in ten which were bred using Al. All twenty were then turned out with a clean-up bull. We had fifteen calves born within the first thirty days (75%) and all twenty conceived a second calf in 1992. Although this method was mostly successful, we felt it involved too much handling.

Before 1992 we investigated and decided to use the thirty-seven day Colorado system of heat synchronization in beef cows. Thirty of our heifers were fed 0.5 mg/head/day of MGA in their grain for fourteen days. After the MGA was withdrawn many of the heifers were noted to be “riding;” an expected but subfertile heat period. Sixteen days after the MGA was withdrawn, each heifer was injected with prostaglandin and given a heat detector patch. The medication costs and the patch came to about $7/head. Our original plan was for the heifers to also receive their Spring vaccinations and wormings at the same time to avoid extra handling. Our veterinarian suggested waiting for at least forty-five days after breeding because he felt that any added stress could affect breeding success.

After forty-eight hours, five heifers showed signs of heat and were bred with AI. Thirteen more were bred at seventy two hours. The remaining twelve were AI’ed after ninety-six hours. In the last group, six still were not showing signs of heat, but were AI’ed anyhow. They all were given a quiet pasture for themselves and a clean-up bull was added after a week.

Pregnancy checks this winter indicated all had conceived, but at least three would be later than the others. The first calf from this group was born 273 days after AI’ing and within the next 12 days we have had 15 more. For us this was simple and successful. We intend to use it again.

Editor’s Note: Since this article was writen several other methods of heat synchronization have been developed. Most breeding services have advice on these at their their web sites. We have also received the following notice: