Two administrations of an intravaginal progesterone device on the induction of ovarian cyclicity in anestrous mares

Abstract

Summary:The study aimed to evaluate the effect of double administration of a progesterone (P4) intravaginal device on induction of ovarian cyclicity in mares. Twelve crossbred mares were assigned to one of two groups. The first group (GP4; n = 6; 100 % in anestrus phase) underwent the following protocol: day (d) 0, 1.9 g of P4 + ultrasound of the uterus and ovaries (US); d 7, US; d10, first P 4 removal + US; d10 -d 24, US daily; d 28, second P4; d 35, US; d 40, second P4 removal + US; d 40 -d 54, US daily; and d 54 -d 76, US every other day. The second group (GNP4; n = 5; 100 % in transition phase) underwent the same protocol as GP4, but without the administration of the P4 device. From d 55 -d 76, 100.0 % of the mares in both groups held uterine tonus and 83.3 % had endometrial edema; after the first and second P4 removal, 66.7 % and 83.3 % of GP4 mares, respectively, reached the transition phase. By d 76, 50.0 % and 80.0 % of the GP4 and GNP4 animals, respectively, had ovulated; the average size of the largest follicle increased from d 0 -d 76 in both groups, but was significant only in GP4. Four to five days after the first and second P4 removals in GP4, follicles showed an average growth of 9.0 mm. At the end of the study, both groups had follicular medium diameters greater than 34 mm (P > 0.05). Ovulations correlated with body condition scores (P < 0.05). In conclusion, two administration of P4 affected ovarian cyclicity in anestrous mares, and synchronized follicular waves and ovulation.

Timed artificial insemination in crossbred mares: Reproductive efficiency and costs

“…PRID has been applied in mares for reversal of anoestrus (Arbeiter et al., 1994; Kaercher et al., 2013) in the transitional phase or in synchronization of oestrus and ovulation (Polo et al., 2016). After the insertion of PRID, there is the emergence of a new follicular wave, with a follicle reaching the dominance phase and resulting in ovulation, making TAI possible (Arbeiter et al., 1994; Polasek et al., 2017).…”

“…The use of PRID helps revert anoestrus and/or the transitional period in mares (Polo et al., 2016), and allows an alternative for the synchronization of ovulation. After removal of PRID, follicular follow‐up until the time of ovulation induction can take 3–8 days, and the embryo recovery rate can reach 75% in inseminated mares (Oliveira Filho et al., 2012; Polasek et al., 2017).…”

Use of Intravaginal Progesterone-Releasing Device Results in Similar Pregnancy Rates and Losses to Long-Acting Progesterone to Synchronize Acyclic Embryo Recipient Mares

“…Therefore, mares were resynchronized three days after the onset of synchronization with IPRD, and all mares had endometrial edema after estrogen treatment. Previous studies, treating seasonal transitional mares with IPRD to hasten cyclicity, demonstrated that mares display endometrial edema and estrus after IPRD removal [ 19 , 20 , 21 , 22 , 46 ]. In clinical practice, it is well-known that mares treated with long-acting altrenogest or LAP4 do not respond to estrogen treatment at the onset of a new synchronization protocol.…”

“…The IPRD are typically made with a silicon matrix loaded with non-synthetic, free (non-bound) progesterone. In horses, IPRD have been used to hasten cyclicity in transitional mares, and to inhibit estrus in cyclic mares [ 19 , 20 , 21 , 22 , 23 ]. Once inserted, IPRD devices rapidly increase progesterone concentration in plasma [ 22 , 24 , 25 ].…”

Two hormonal protocols for timed artificial insemination in mares under different residence times of the progesterone intravaginal device

“…A new follicular wave emerges about 3.5 to 5 days after estradiol benzoate administration (Moreno et al 2001, Bó et al 2002. The PRIDs have been used in horses in the anoestrus phase (Polo et al 2016) or the transitional phase at the beginning of the breeding season, aiming to synchronise the first ovulation, anticipating the beginning of the season (Wilde et al 2002, Handler et al 2007, Hanlon and Firth 2012.…”