Use of long-acting progesterone to acyclic embryo recipient mares

Abstract

-The objective of this study was to evaluate the efficiency of cyclic and acyclic progesterone-treated recipient mares in a commercial embryo transfer program. Acyclic recipients were treated with decreasing amounts of estradiol cypionate (ECP ® -Pfizer Saúde Animal, São Paulo, Brazil), followed by 1500 mg of a sustained-release progesterone injection (P4LA150 ® -Laboratórios B.E.T., Rio de Janeiro, Brazil). Out of all 1506 embryo recovery attempts performed, 59.36%were positive (894/1506). Pregnancy rates of cyclic and acyclic mares were, respectively, 44.12% (319/723) and 57.68%(139/241) -higher in acyclic recipients under progesterone treatment. Embryo loss was similar between groups (9.72% -31/319 vs. 11.51% -16/139). When fertility data on acyclic mares treated with long-action progesterone were grouped in relation to the interval of the beginning of the treatment with progesterone to the embryo transfer, there was no difference in pregnancy rates at 12 days (51.28% -20/39; 58.92% -33/56; 60.52% -46/76 and 58.57% -41/70 for embryos transferred 3 (P3), 4 (P4), 5 (P5) and 6 (P6) days after the beginning of the treatment with progesterone). Groups P3, P4, P5 and P6showed embryo loss rates of 20.00% (4/20), 12.12% (4/33), 2.17% (1/46) and 17.07% (7/41), respectively. These rates were similar in groups P3, P4 and P6. Pregnant recipients submitted to an embryo transferring procedure on P5 showed lower embryo mortality rates than on P3 and P6. P4 recipients tended to suffer higher embryo mortality rates than P5. Acyclic recipient mares under progesterone treatment can be satisfactoryly used in embryo transfer programs.

Synchronization of cyclic and acyclic embryo recipient mares with donor mares

“…Reported synchronization protocols may involve the use of prostaglandin F2α (i.e., dinoprost tromethamine) or its analogs (e.g., sodium cloprostenol), steroid hormones (progestins and estrogens), and ovulation induction agents such as human chorionic gonadotropin and GnRH agonists (e.g., deslorelin acetate, histrelin) (Carnevale et al, 2000;McCue et al, 2002;Rocha Filho et al, 2004;Carnevale et al, 2005;Caiado et al, 2007;Fleury et al, 2007;Greco et al, 2008;Greco et al, 2012;Kaercher et al, 2013;McCue and Squires, 2015;Greco et al, 2016;Pinto et al, 2017). Prostaglandin F2α alone is commonly used in cyclic mares to bring them back into estrus when necessary (Cuervo-Arango et al, 2017).…”

“…Prostaglandin F2α alone is commonly used in cyclic mares to bring them back into estrus when necessary (Cuervo-Arango et al, 2017). Whereas, a combination of estrogen (e.g., estradiol 17β, estradiol benzoate, or estradiol cypionate) and progestin (e.g., altrenogest, or progesterone) is typically used in acyclic and transitional recipient mares or when there is a shortage of recipient mares, demanding a tight-synchrony between one embryo donor and one or two of its recipients (Rocha Filho et al, 2004;Greco et al, 2012;McCue and Squires, 2015;Silva et al, 2017;Pinto et al, 2017).…”

Administration of 2.5 mg of estradiol followed by 1,500 mg of progesterone to anovulatory mares promote similar uterine morphology, hormone concentrations and molecular dynamics to those observed in cyclic mares

“…In the past few years, various doses of E2 has been given to intact non-cyclic recipient mares and after observation of uterine edema, long acting progesterone (LA P4) [6,7] or altrenogest [2,9] has been administered three to eight days prior to embryo transfer. Recently, it was demonstrated that the administration of a single dose of 2.5 mg of estradiol benzoate to anestrous mares produces similar estrogen concentration to that found in cyclic mares [10].…”

Ultrasonography of the conceptus development from days 15 to 60 of pregnancy in non-cyclic recipient mares

“…The use of non-cyclic recipient mares in ET programs and their pregnancy rates have been described in the literature (CARNEVALE et al, 2000;GRECO et al, 2012;. However, there are no reports on the developmental pattern of conceptuses transferred to these recipients during early pregnancy.…”

“…Most of the studies demonstrate that pregnancy and early embryonic death rates of non-cyclic recipient mares are similar to those of cyclic recipients, and thus can be successfully used in ET programs (CARNEVALE et al, 2000;ROCHA FILHO et al, 2004;GRECO et al, 2012;. In addition, the use of non-cyclic recipient mares is an advantageous alternative to horse owners and veterinarians, since it enables the anticipation and/or prolongation of the breeding season (GRECO et al, 2012), eliminates the need for synchrony of ovulation between donor and recipient and reduces the number of recipients per donor (MCKINNON et al, 1988).…”