Animal Reproduction (AR)
Animal Reproduction (AR)
Original Article

Transfer of equine embryos into anovulatory recipients supplemented with short or long acting progesterone

A.N. Rocha Filho, M.A. Pessôa, M.M. Gioso, M.A. Alvarenga

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Pregnancy and early embryonic death rates in cycling and noncycling progesterone-treated recipient mares were examined in a retrospective study. During three breeding seasons, 264 embryos were transferred into either cycling (control, n=152) or noncycling (n=112) mares in a commercial embryo transfer program in Brazil. The anovulatory mares were treated with either 200 mg/day (Treatment 1, n=54) or 400 mg/every other day (Treatment 2, n=13) short acting progesterone, or 1500 mg long acting progesterone every 7 (Treatment 3, n=30) or 6 (Treatment 4, n=15) days. Embryos were transferred non-surgically into cycling recipients 4 to 8 days after ovulation and 5 to 8 days after the beggining of progesterone supplementation into anovulatory mares. Pregnancies were checked on days 12, 25 and 50 by transrectal ultrasonography. Data were analyzed by Chi-square. Pregnancy rates on days 12 (75.0, 75.9, 76.9, 76.6 and 73.3%) and 50 (61.8, 61.1, 61.5, 53.3 and 60.0%) as well as embryonic death rates (17.5, 19.5, 20.0, 30.4 and 18.2%) were similar (P>0.05) for control mares and treatments 1, 2, 3 and 4, respectively, and between control and all anovulatory mares combined. Concerning pregnancy and embryonic death rates in anovulatory recipients, similar (P>0.05) results were obtained after embryo transfers into recipients receiving short or long acting progesterone for 5 to 8 days before transfer, as well as after transfers performed during spring or fall and during winter. Additionally, daily administration of short acting injectable progesterone provided similar (P>0.05) results as administration of a high dose (400 mg) on alternate days. In conclusion, anovulatory mares treated with short or long acting progesterone for 5 to 8 days before transfer can be successfully used as embryo recipients during the period of the year in which few cycling recipients are available.


progesterone, mares, anovulatory, embryo transfer, recipients
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