Intrafollicular Injection of Prostaglandins in the Preovulatory Follicle of the Mare

AGUILAR, J.; CASTAÑEIRA, C.; ALONSO, C.; FLORES, A.; MARÍN, J.; CUERVO-ARANGO, J.; MARTINEZ-BOVÍ, R.; MOUGUELAR, H.; LOSINNO, L.

JOURNAL OF EQUINE VETERINARY SCIENCE

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2018 vol. 66

0737-0806

The exact role of prostaglandins during the ovulatory process inmammals is not completely understood. This experiment wasperformed to evaluate whether intrafollicular treatment withPGE2 and PGF2a administered in early to mid-oestrus (folliclediameter between 35-39 mm), would induce normal ovulation,corpus luteum formation and development, progesterone production, fertilization and embryo development. Six mixed-bredcyclic mares aged 3 to 12 years old and weighing between 350 and550 Kg were studied during 3 oestrous cycles each, betweenSeptember 2017 and January 2018. The reproductive tract wasexamined transrectally using a B-mode ultrasound scanner(Sonoscape A6) with a 5-MHz linear array probe. Ultrasound examinations were performed every day from Day 15 (Day 0 ¼ day ofovulation) until intrafollicular injection (Hour 0). Mares wererandomly assigned to a control group (no puncture), puncturecontrol and puncture treatment group in a crossover design. Whenfollicle diameter reached 35 mm and the uterus showed mild tomoderate endometrial oedema (score of 2-3 out of 5) a bloodsample was taken from the jugular vein and the preovulatoryfollicle was injected with 500 mg PGE2 (dinoprostone 10 mg/mL;Prostaglandin E2; Pfizer) and 125 mg PGF2a (Lutalyse tromethamine 5 mg/mL; Dinolytic; Pfizer) diluted in 0.5 mL of sterile water(treatment cycles) or a placebo (0.5 mL of water only, puncturecontrol). The intrafollicular puncture was performed ultrasoundguided through the flank with the mare restrained in stocks, aftersedation with an i.v. dose of 0.01 mg/Kg detomidine hydrochlorideand 0.02 mg/Kg i.v. butorphanol tartrate. Mares were inseminatedwithin 2 h after puncture with fresh extended semen containing1 x 109 motile sperm cells. There were no significant differences (Pvalue¼ 0.51) for pregnancy rate among the three groups: control50% (3/6); puncture control 66.7% (4/6) and treatment group 33.3%(2/6). However, 5 out of 6 treated follicles ovulated within 12 h; theintrafollicular puncture-ovulation interval was significantly (Pvalue ¼ 0.0031) shorter for the treatment group versus control andpuncture control (18.014.7 vs 6828.1 and 9050.8 h, respectively). Follicle size was not different (P-value¼ 0.58) among thethree groups (35.61.2, 35.30.8 and 34.91.8mm respectively),at the time of puncture. Day 15 vesicle diameter in the treatmentgroup was smaller (8.7 mm) than the control groups (12.2 and 19.2mm). Based on these results it can be concluded that intrafollicularinjection through the mare?s flank with water or with a mixture ofprostaglandins does not prevent oocyte release. In addition,intrafollicular injection of prostaglandins (E2 and F2a) hastened thetime to ovulation by more than 50 h compared to the controls.