b'REAL-WORLD RESEARCHof the cycling mare, with efficient pro-Furosemide Use and Long-Term Calcium Balance duction and high stability, said Roser. She said the unique benefits of reFSH Furosemide (aka Lasix) is a controversial drug in U.S. racehorsesnot only for its poten- and reLH include:tial performance-enhancing effects but also because studies have shown it can alter horses reLH induces timely ovulations and calcium balance, which is important for bone strength and muscle contraction.increases the number of ovulations;So Abby Pritchard, a PhD candidate in Michigan State Universitys Department of Animal reFSH increases the number of fol-Science, in East Lansing, measured how long it takes a horses calcium balance to return tolicles, ovulations, and embryos for baseline after furosemide administration.transfer, helping subfertile mares get Veterinarians administer furosemide to horses on race days to prevent exercise-inducedpregnant; andpulmonary hemorrhage (EIPH, bleeding of the blood vessels in the lungs). Because its reFSH induces superovulation in a diureticincreasing urinationit can cause a horse to drop weight rapidly, a possible performance-enhancing side effect. Increased urine output also increases sodium andcycling mares as well as those in deep calcium losses. anestrus, allowing them to get pregnant In her crossover study Pritchard compared calcium levels in five mature Standardbredsor produce multiple embryos in the receiving furosemide and in five controls. The treatment horses received one standard dosenonbreeding season.of the medication, after which she collected and measured both groups urine and manureThe question now remains as to output for seven days. After a two-week washout period, she swapped treatment and controlwhether these recombinants will enhance group horses and repeated the experiment. Based on her results she found: reproductive efficiency by increasing theNo difference in horses fecal output or fecal calcium levels; number of viable oocytes for ICSI, OT, Treated horses urinated more than twice as much as control horses on Day 1, then theGIFT, and cloning, Roser said.frequency dropped back to normal;Treated horses urine calcium levels were twice as high as the controls on Day 1, but they7 Facts About Horses Circadian and returned to normal by Day 3; and Circannual RhythmsAny negative effects of furosemide on calcium balance were almost gone by Day 3 andNearly all organisms, including horses, disappeared completely by Day 5 adapt their lifestyles to the timing of Most of the calcium balance effects seen are driven by urine output and calcium loss onsunrise and sunset. These light and dark Day 1, said Pritchard. cycles result in daily (circadian) and These findingsthat calcium levels return to baseline within five dayssuggest thatannual (circannual) rhythms of physiol-weekly furosemide administration in racehorses doesnt lead to long-term calcium lossesogy and behavior. And, as a researcher in that might contribute to skeletal injuries, she said. Ireland recently reported, understanding how horses respond to these cycles can help you manage them accordingly. University of California, Davis, Depart- 4. Gamete intrafallopian transfer (GIFT),Barbara Murphy, PhD, assistant profes-ment of Animal Science, describedduring which the vet transfers both thesor in University College Dublins School current technologies and a new hormonesperm and the mature oocytes into theof Agriculture and Food Science, has stud-therapy that has the potential to makerecipient mares oviduct. This is usefulied circadian and circannual rhythms and them even more effective: recombinantfor mares with reproductive problemshow they affect horses. Here are sevenequine gonadotropins. and stallions with low sperm numbers. take-homes from her lecture:First, Roser listed ART techniques and5. Cloning, or producing genetically iden- 1. Daily external signals, such as the their limitations. tical horses.light-dark cycle, feeding times, and 1. Embryo transfer (ET), which involvesAll these reproductive technologiesexercise patterns, can synchronize removing an embryo from a donorbenefit from multiple ovulations. Onehorses circadian rhythms. Circannual mare and placing it in a recipientway to achieve this is through superovu-mares uterus to carry to term. Its alation, in which the veterinarian admin-common way breeders get foals fromisters specific hormones to the mare that performance mares or mares withstimulate her ovaries to produce multiple health problems. follicles. We disrupt horses internal 2. Intracytoplasmic sperm injection (ICSI),A variety of hormone therapies exist to the direct injection of sperm into ainduce ovulation, but drawbacks includerhythms when we interact mares mature oocyte (egg). Vets mightinconsistent performance, significant ex- with them at nightto use this technique in mares with repro- pense, low stability, and variable results.ductive abnormalities or disease.With the advent of recombinanttoss hay, do night check, 3. Oocyte transfer (OT), which works liketechnology, two relatively new stimulat-embryo transfer, but with an egg rathering agents, recombinant equine folliclemedicate, or change than an embryo. Veterinarians mightstimulating hormone (reFSH), with orbandages, for instance. use this technique in mares with ovi- without recombinant equine luteinizing duct problems, uterine infections, tornhormone (reLH), have been developed cervices, and other conditions.and reported to superovulate the ovaries 24October 2019The Horse | TheHorse.com'