REPRODUCTION REPORT
SETTING FEMALES UP FOR SUCCESS: ESTRUS SYNCHRONIZATION
by Carson Anderson, University of Missouri graduate research assistant Estrus synchronization is a reproductive technology that can add value to your program. Using this technology can control and shorten the breeding and the subsequent calving season, increase uniformity of the calf crop, and provide an effective way to use artificial insemination. How much value you can generate from using estrus synchronization will vary from operation to operation. Although, it can’t be emphasized enough: estrus synchronization will not make up for females in poor body condition, poor management, or poor health. Instead, think of estrus synchronization as an added boost rather than as a crutch or as a cover up for other management problems. Heifers and cows will require different management strategies to be successful in an estrus synchronization program. Let’s start with heifers. Bos indicus-influenced heifers should be developed to 65% of their mature cow weight at the time of breeding. This will help ensure that a large percentage of heifers will become pubertal by the start of the breeding season. However, keep in mind that developing to target weight isn’t going to guarantee heifers will be pubertal at the time of breeding. Consider having a veterinarian perform an evaluation of the reproductive tract four to six weeks prior to breeding to identify poor candidates for estrus synchronization. When managing cows for success in an estrus synchronization program, we are mainly thinking about their body condition, plane of nutrition, and how long it has been since calving. Cows should be managed so that they are at a body condition score of 5 or greater at the time of breeding and need to be gaining rather than losing weight. A positive plane of nutrition is critical for getting cows to resume normal estrous cycles after calving. Remember, it is common
that cows are near peak lactation and will have increased nutritional requirements around the time of breeding. If you are calving during a time of year in which you can’t meet her nutritional requirements just off of the current forage base, supplementation will be necessary for maximum fertility. Meeting nutritional requirements is even more critical for younger cows that are still growing themselves while also nursing their calves. It takes time to resume normal estrous cycles, and cows are more likely to be cycling at the start of the synchronization program when they have had more time after calving. In general, we want to see cows averaging at least 45 days postpartum by the time of breeding. If you are using CIDRs in your estrus synchronization program, cows should be at least 21 days after calving at the time of CIDR insertion. Cows with shorter days postpartum are not as likely to breed to artificial insemination compared with cows with increased days postpartum, but it is usually still worth trying to get them jump-started with synchronization. Herd health is an important factor that can strongly influence a female’s ability to perform during breeding season. Heavy parasitization and other disease challenges can dramatically impact reproductive performance. Consult with your veterinarian for the best health protocol for your operation. In general, prebreeding booster vaccinations should be administered at least 30 days prior to breeding. Estrus synchronization is an investment that can increase productivity in your herd and profitability in your business. However, in order to capture the value of what estrus synchronization can bring to your operation, it is important to set your females up for success.
