Control of Estrus and Ovulation in Heifers
MGA- and CIDR®-based synchronization protocols can be used to get more heifers bred earlier in the breeding season.
by Lynsey Meharg for Angus Journal
STAUNTON, Va. (Oct. 15, 2013) — When Dave Patterson, University of Missouri–Columbia animal science professor, first began studying synchronization protocols for heifers, he was skeptical, he told cattlemen gathered at the Applied Reproductive Strategies in Beef Cattle (ARSBC) Symposium in Staunton, Va., Oct. 15-16. However, after studying the subject extensively, he said he is now confident that the advantages offered are well worth the effort.
“Heifers that conceive earlier in their first breeding season typically stay in the herd longer and produce more pounds of beef over their productive lifetimes,” said Dave Patterson, University of Missouri.
“What we know from large data sets gathered over the last 40 years is heifers that conceive earlier in their first breeding season typically stay in the herd longer and produce more pounds of beef over their productive lifetimes,” said Patterson. Estrous synchronization can be used to get more heifers pregnant during the first 21 days of the breeding season.
Patterson shared the current status of research on synchronization protocols for beef heifers, detailing the pros and cons of several MGA- and CIDR®-based protocols suggested by the Beef Reproduction Task Force. Significant progress has been made during the last 10-15 years, he said, moving away from systems that require heat detection toward opportunities for fixed-time artificial insemination (AI). (His comparisons of the products are available in the proceedings, PowerPoint and audio posted with his presentation summary in the Newsroom at www.appliedreprostrategies.com/2013.)
Fundamental to the success of any synchronization and AI protocol is proper heifer development prior to the first breeding season. Patterson called five key factors critical to the success of heifer-development programs:
- target weight;
- reproductive tract scores;
- pelvic measurements;
- estrous synchronization; and
- sire selection (considering birth weight and calving ease EPDs).
Prebreeding evaluations allow producers to evaluate how good of a job has been done in preparing heifers for their first breeding season, said Patterson. Prebreeding exams assess heifer weight, along with reproductive and skeletal development.
“In my opinion they’re very critical,” he said. “They’re not only ensuring success for one year, but furthering opportunities to see that producers actually continue utilizing synchronization and AI in subsequent years.”
Skeletal development, determined by pelvic measurements, plays a part in determining the level of calving difficulty a heifer will experience.
Reproductive development is assessed by evaluation the reproductive tract and assigning a reproductive tract score (RTS) on a scale of 1 to 5, 1 being an infantile reproductive system and five being a female who is cycling in the luteal phase and has a palpable CL.
Patterson recommended gathering prebreeding RTS four to six weeks before breeding or two weeks before synchronization. Synchronization protocols shouln’t be initiated until at least 50% of the heifers have an RTS of 4 or 5.
Over the course of the next several years, Patterson said, he believes more producers will begin pulling heifers from backgrounding lots to use as replacements. He cautioned producers about selecting females that have been previously implanted, citing the long-term effects of MGA-based protocols on females.
Smith spoke during Tuesday's ARSBC session focused on management influences on the success of AI programs. Visit the Newsroom at www.appliedreprostrategies.com to listen to his presentation, view his PowerPoint slides and proceedings paper, or access the synchronization protocols recommended for heifers by the Beef Reproduction Task Force.
Comprehensive coverage of the 2013 ARSBC symposium is available online at www.appliedreprostrategies.com. Compiled by the Angus Journal editorial team, the site is made possible through sponsorship by the Beef Reproduction Task Force.