The Horse

MAR 2018

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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YOUR GUIDE TO THE 2017 AAEP CONVENTION SPONSORED BY A32 TheHorse.com/AAEP2017 AAEP Wrap-Up THE HORSE March 2018 embryo recovery attempts) on every other mare. They recovered embryos in 46.2% of attempts with complete flush media and 57.1% of attempts with Hartmann's. On Days 14 and 25 they performed pregnancy exams on recipient mares and found that results with the complete flush media and Hartmann's solution groups were essentially the same: 80.5% and 80.8% pregnant, respectively, on Day 14, and 78% and 76.6% pregnant on Day 25. Therefore, veterinarians have multiple media type options for embryo recovery. "Ambulatory vets can carry one type of media (Hartmann's solution) for both uterine lavage and embryo transfer," said Ferris, adding that Hartmann's solution might also be more cost-effective. 2. What options are available if a cycling recipient mare is not available? "One of the more important factors affecting the likelihood of establishing a pregnancy after embryo transfer is donor- recipient synchrony," said Ferris. In other words, the donor and recipient mares' estrous cycles must be in sync. Ideally, the recipient ovulates one day before to three days after the donor does. However, many clinics don't have a large enough pool of cycling recipient mares to match the donor population, particularly when it's early in the breeding season. In these situations, vets commonly administer hormones to recipients to mimic the rising estrogen from growing follicles and rising progesterone levels after ovulation. But how does this affect pregnancy rates? To find out, Ferris et al. transferred: ■ 65 embryos into naturally cycling recipient mares; ■ 40 embryos into noncycling mares treated with two days of estrogen to mimic estrus, followed by five to seven days of progesterone to support the pregnancy; and ■ 14 embryos into naturally cycling mares early in estrus (without a domi- nant follicle) treated with the afore- mentioned hormone therapy. Ferris said there was no statistically significant difference between pregnancy rates among all groups. "Estrogen and progesterone in non- cycling recipient mares can result in a similar pregnancy rate as recipients with natural ovulation," he said. "Hormone therapy can be especially advantageous for matching a specific recipient with a donor mare." 3. Does the recipient have enough proges- terone to support pregnancy? The mare's corpus luteum (the struc- ture formed after ovulation) produces progesterone that's critical to maintaining pregnancy. The minimum level of pro- gesterone needed to support a pregnancy is approximately 2.5 ng/mL. It's been as- sumed that recipient mares' progesterone levels five days after ovulation are above 4 ng/mL, said Ferris. To confirm this, his team evaluated progesterone production in 456 recipient mares with normal detectable ovulations five days post-ovulation. They found that 5.5% had levels below 4 ng/mL and 0.9% had levels below 1 ng/mL, the latter indi- cating a corpus luteum never formed. "Normal corpus luteum function after ovulation does not occur in a small per- centage of mares," said Ferris. Overall, he said, "these techniques can allow clinicians greater flexibility to over- come common challenges in embryo re- covery and recipient mare management." What's the Best Way to Predict Foaling? It takes approximately 11 months from conception for a mare to produce a foal— emphasis on the word approximately. Anyone who's waited long nights for foals to arrive knows mares' gestation lengths can vary substantially. While caretakers can use various methods to predict foal- ing, some are more accurate than others. A research team led by Mariana Diel de Amorim, DVM, DVSc, Dipl. ACT, now lecturer in theriogenology at the Cornell University College of Veterinary Medicine, in Ithaca, New York, set out to compare foaling prediction methods. Ma- donna Morrison, DVM, a recent gradu- ate of the University of Prince Edward Island's Atlantic Veterinary College, in Canada, and a member of the team, pre- sented the results. They collected mam- mary secretions from 40 Standardbred mares starting between Day 320 and Day 330 of gestation and tested several foaling prediction methods, including: ■ The calcium titration method (measur- ing the secretions' calcium concentra- tions, which rise significantly from 72 to 24 hours before foaling); ■ A digital pH meter (mammary secre- tions normally have a pH above 7; when they drop to below 7, the mare will likely foal within 24 hours); ■ pH test strips (the same concept as us- ing a digital pH meter, but using com- mercially available test strips); ■ Water hardness test strips (which mea- sure calcium and magnesium); ■ A Brix refractometer (measures colostrum-specific gravity, which rises as mares get closer to foaling); and ■ A commercially available foaling moni- toring system. The team used Foalert, which is sewn onto the mare's vulva lips to detect separation by the foal. They analyzed samples from three days (Day -3) before foaling to foaling (Day 0) and found significant differences between the tests on Days -3, -1, and 0: ■ "Both the calcium titration and pH methods (seem) to be the best meth- ods" for predicting foaling, Diel de Amorim told The Horse; ■ The foaling monitoring system alerted the team when 82% of mares were foal- ing; it produced "false alarms" 19% of the time. Elizabeth Schilling @efsdvm Only during #AAEP2017 do you hear "optimal insemination" in casual conversation as you walk past the bar. COURTESY DR. RYAN FERRIS A healthy embryo recovered from embryo transfer.

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