Proceedings of the 5th International Symposium on EQUINE ...

Havemeyer Foundation Monograph Series No. 3IMPROVEMENT OF OVARIAN SUPERSTIMULATORYRESPONSE AND EMBRYO PRODUCTION IN MARESTREATED WITH EPE TWICE DAILYM. A. Alvarenga, P. McCue*, E. L. Squires* and J. R. Neves NetoDepartment <strong>of</strong> Animal Reproduction and Veterinary Radiology-Scholl <strong>of</strong> Veterinary Medicine andAnimal Science, UNESP –Botucatu –SP –Brazil-18618; *Animal Reproduction and BiotechnologyLaboratory, Colorado State University, Fort Collins, Colorado 80523, USAINTRODUCTIONEquine pituitary extract (EPE) is <strong>the</strong> onlycompound that has been reported to consistentlyinduce multiple ovulation in horses. However, <strong>the</strong>superovulatory response in mares treated withEPE, is far lower than <strong>the</strong> response obtained ino<strong>the</strong>r species. Ovulation rates <strong>of</strong> 1.7 to 3.8ovulations per cycle have been reported after EPEtreatment in mares (McCue 1996).In cows, <strong>the</strong> superovulatory response is moreconsistent when FSH is injected twice daily thanonce daily (Monniaux et al. 1983). On <strong>the</strong> firstreport <strong>of</strong> successful superovulation in maresDouglas et al. (1974) used EPE twice daily inseasonally anovulatory mares, a subsequentpublication from <strong>the</strong> same laboratory showedsimilar response using EPE once daily (Lapin andGin<strong>the</strong>r 1977). Since <strong>the</strong>n, <strong>the</strong> protocol used toinduce multiple ovulations in mares consist <strong>of</strong> oncedaily EPE administration. Attempts to improve <strong>the</strong>effectiveness <strong>of</strong> EPE for induction <strong>of</strong> supeovulationin mares have focused on <strong>the</strong> <strong>the</strong> daily dose (Woodsand Gin<strong>the</strong>r 1982), time <strong>of</strong> treatment initiation(Dippert et al. 1992) and utilisation <strong>of</strong> purifiedfraction <strong>of</strong> equine FSH (Rosas et al. 1998). Ourrecent study had demonstrated that more frequentdaily injections <strong>of</strong> EPE increased ovarian responseto EPE (Alvarenga et al. 1999). The purpose <strong>of</strong> <strong>the</strong>present experiment was to compare superovulatoryresponse and embryo recovery rates <strong>of</strong> cyclingmares follow EPE administration once and twicedaily.MATERIALS AND METHODSEquine pituitary extract (EPE) was prepared atColorado State University utilising a methodpurposed by Guillou and Combarnous (1983).Seven days after ovulation mares were treatedwith PGF2 (Dinoprost 10 mg) administeredonce, im and <strong>the</strong>n randomly assigned to one <strong>of</strong> 2treatments: Group 1 (n=8) received 25 mg <strong>of</strong> EPEonce daily and Group 2 (n=8) treated with 25 mg<strong>of</strong> EPE 2 times daily (8 am and 6 pm) given im.For both group <strong>of</strong> mares <strong>the</strong> treatment wasdiscontinued when at least half <strong>of</strong> >30 mmdetected follicles reached 35 mm and 2,500 iu <strong>of</strong>hCG was administered iv.Mares were inseminated daily, until ovulation,with semen from a fertile Arabian stallion.Embryo recovery was performed 8 days afterovulation. On <strong>the</strong> day <strong>of</strong> embryo recovery bloodsamples were collected to determine differences in<strong>the</strong> circulating levels <strong>of</strong> progesterone in mareswith different number <strong>of</strong> ovulations.RESULTSA higher number <strong>of</strong> ovulations occurred and alarger number <strong>of</strong> embryos were recovered in marestreated twice daily than those treated once daily(P