Short communication: Establishment and maintenance of donkey-in-mule pregnancy after embryo transfer in a non-cycling mule treated with oestradiol benzoate and long-acting progesterone

Marina Bottrel, Thomaz Fortes, Isabel Ortiz, Manuel Hidalgo, Jesús Dorado


Female mules are considered as infertile; however, they could be used as recipients in interspecific embryo transfer. This study reports for the first time how it is possible to obtain the birth of a live Andalusian donkey foal after transfer a donkey embryo to a non-cycling mule. Two non-cycling mules were used as recipients, oestradiol benzoate was administered when donors showed oestrus and long-acting progesterone after ovulation. The mules also received long-acting progesterone every 7 days until 120 days of gestation. One embryo was collected from the two donor jennies and transferred to one of the mules after 5 days of progesterone treatment. Pregnancy was established and maintained after embryo transfer. The pregnant mule carried to term and delivered a live donkey foal after 375 days of pregnancy. In conclusion, non-cycling mules treated with oestradiol benzoate and long-acting progesterone can be successfully used as recipients of donkey embryos, which open new ways for the conservation of endangered donkey species.


between-species embryo transfer; donkey embryo; mule recipient; Andalusian donkey

Full Text:



Allen WR, 2005. The development and application of the modern reproductive technologies to horse breeding. Reprod Domest Anim 40 (4): 310-329.

Allen WR, Kydd DF, Antczak DF, 1993. Intraspecies and extraspecies equine pregnancies. In: Equine Reproduction; McKinnon AO, Voss JL (eds.). pp: 536-553. Lea & Febiger, Philadelphia.

BOE, 2009. Royal decree 2129/2008, of 26 December, that establish the national program for conservation, improvement and promotion of livestock breeds. Boletín Oficial del Estado [Spain] No. 23, 27/01/09.

BOE, 2013. Royal decree 53/2013, of 1 February, that establish the basic rules to protect animals used in experiments and for other scientific purposes, including teaching. Boletín Oficial del Estado [Spain] No. 34, 08/02/13.

Botelho JHV, Pessoa GO, Rocha LGP, Yeste M, 2015. Hormone supplementation protocol using estradiol benzoate and long-acting progesterone is efficient in maintaining pregnancy of anovulatory recipient mares during autumn transitional phase. Anim Reprod Sci 153: 39-43.

Bryant U, Fallon L, Lee M, Pool R, 2012. Congenital aneurysmal bone cyst in a foal. J Equine Vet Sci 32 (6): 320-323.

Bucca S, 2005. Equine fetal gender determination from mid- to advanced-gestation by ultrasound. Theriogenology 64 (3): 568-571.

Camillo F, Vannozzi I, Rota A, Di Luzio B, Romagnoli S, Aria G, Allen WR, 2003. Successful non-surgical transfer of horse embryos to mule recipients. Reprod Domest Anim 38 (5): 380-385.

Camillo F, Panzani D, Scollo C, Rota A, Crisci A, Vannozzi I, Balbo S, 2010. Embryo recovery rate and recipients' pregnancy rate after nonsurgical embryo transfer in donkeys. Theriogenology 73 (7): 959-965.

Carnevale EM, Ramirez RJ, Squires EL, Alvarenga MA, Vanderwall DK, McCue PM, 2000. Factors affecting pregnancy rates and early embryonic death after equine embryo transfer. Theriogenology 54 (6): 965-979.

DAD-IS-FAO, 2014. Information system domestic animal diversity. [Jan 9, 2017].

González SM, Gomes RG, Souza AK, Silva CB, Silva-Santos KC, Seneda MM, 2015. Evidences of regular estrous cycles in mules and successful use of these animals as recipients for donkey embryos. J Equine Vet Sci 35 (10): 869-872.

Kaercher F, Kozicki LE, Camargo CE, Weiss RR, dos Santos IW, Muradas PR, Bertol MAF, de Abreu RA, 2013. Embryo transfer in anovulatory recipient mares treated with estradiol benzoate and long-acting progesterone. J Equine Vet Sci 33 (3): 205-209.

Panzani D, Rota A, Crisci A, Kindahl H, Govoni N, Camillo F, 2012. Embryo quality and transcervical technique are not the limiting factors in donkey embryo transfer outcome. Theriogenology 77 (3): 563-569.

Peña-Alfaro CE, Barros LO, Carneiro GF, Gastal MO, Gastal EL, 2014. Embryo transfer in Pega donkeys (Equus asinus) in Brazil. J Equine Vet Sci 34 (1): 185.

Rocha Filho AN, Pessoa MA, Gioso MM, Alvarenga MA, 2004. Transfer of equine embryos into anovulatory recipients supplememted with short or long acting progesterone. Anim Reprod 1 (1): 91-95.

Silva AR, Gomes RG, Gonzalez SM, Barreiros TRR, Seneda MM, 2013. Pregnancy after transfer of donkey embryo in cycling mule as recipient. Anim Reprod 10 (3): 500.

Squires EL, Carnevale EM, McCue PM, Bruemmer JE, 2003. Embryo technologies in the horse. Theriogenology 59 (1): 151-170.

Stout TAE, 2006. Equine embryo transfer: review of developing potential. Equine Vet J 38 (5): 467-478.

Summers PM, Shephard AM, Hodges JK, 1987. Successful transfer of the embryos of Przewalski's horses (Equus przewalskii) and Grant's zebra (E. burchelli) to domestic mares (E. caballus). J Reprod Fertil 80 (1): 13-20.

DOI: 10.5424/sjar/2017154-11653