Pregnancy Determination in Cattle:
A Review of Available Alternatives
JOPLIN, Mo. (Sept. 1, 2011) — The simplest and most direct way to pregnancy-test is to wait until the cow gives birth, but economics push herd managers to diagnose the condition much sooner.
Discarding one other simple solution, University of Missouri (MU) dairy scientist Matt Lucy said, “After AI (artificial insemination), the cleanup bull does the best job of finding which cows didn’t get bred — if only he would write down the numbers.”
Lucy presented more feasible alternatives Thursday, Sept. 1, at the Applied Reproductive Strategies in Beef Cattle (ARSBC) meeting in Joplin, Mo. With today’s more intensive management strategies — such as heat synchronization and fixed-time AI (FTAI), “the next frontier in beef is a second synchronized AI,” he said.
Although rectal palpation is the most widely used means of pregnancy diagnosis, even its soonest possible result 30-35 days after AI is too late for practicality. Ultrasound is not much better, typically applied after Day 30. Both require experienced veterinarians, which are not always available to fit the schedules and remote areas, Lucy noted.
That leads to consideration of biochemical tests. Unlike humans, cows do not produce a tell-tale hormone in urine, but unique molecules circulate in bovine blood at certain times in the early days of pregnancy. Research is looking at ways to detect an “early conception factor” within days of breeding, but no tests are yet available.
Further out, there are blood tests based on interferon (Day 16-18); progesterone in blood or milk (Day 18-23); and pregnancy-associated glycoproteins, or PAG (after Day 25). In general, the later means are more accurate.
Most producers can easily collect blood samples and use a commercial indicator test on a convenient schedule to allow that second heat synchronization and rebreeding as soon as 28 days after the first AI, Lucy said.
The economics of such an intense breeding program would depend on genetic values and alternatives, but it would require reinsertion of CIDRs in all candidates for rebreeding on Day 19 post AI, with removal and blood tests on Day 26 with prostaglandin and FTAI with GnRH 54 hours later.
Even for cattlemen not practicing AI, blood samples of cows at weaning could eliminate the need for a veterinary appointment and manual pregnancy checking, Lucy pointed out.
Lucy spoke during Thursday's ARSBC session focused on current topics in reproductive management. Visit the Newsroom at www.appliedreprostrategies.com to view the PowerPoint slides and proceedings paper submitted by Lucy to accompany his presentation. Audio of the presentation will be available soon.
Comprehensive coverage of the symposium is available online at www.appliedreprostrategies.com. Compiled by Angus Productions Inc. (API), the site is made possible through sponsorship by the Beef Reproductive Task Force, SEK Genetics, and liveauctions.tv. Coverage includes summaries of the speaker presentations, PowerPoints, proceedings and audio.
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