Ultrasonography of the conceptus development from days 15 to 60 of pregnancy in non-cyclic recipient mares/Ultrassonografia do desenvolvimento do concepto entre 15 e 60 dias de gestacao em eguas receptoras aciclicas

The present study evaluated the development of equine conceptus transferred to non-cyclic recipient mares treated with altrenogest. Twenty four mares were used as embryo recipients during the ovulatory phase (Control group; n=8) or anestrus/transitional phases (Altrenogest group; n=16) and were evaluated by transrectal ultrasonography, at five day intervals, to monitor the development of embryonic vesicles from 15 to 45 days of pregnancy and embryo proper/fetus from 20 to 60 days. Embryonic vesicle's features such as shape, embryo location within the vesicle and umbilical cord development were similar between cyclic and non-cyclic recipient mares. The embryonic vesicle and embryo proper/fetus growth was significant (P0.05). The embryonic vesicle and embryo proper/ fetus growth was similar (P>0.05) when gestational days were compared between groups. The similarity in conceptus growth between cyclic and non-cyclic recipient mares during early pregnancy indicates that the uterine environment of non-cyclic recipient mares treated with progestins provides similar conditions for the development of transferred embryos. Key words: altrenogest, non-cyclic recipient mares, embryonic vesicle, embryo proper, fetus. O presente trabalho avaliou o desenvolvimento de conceptos equinos transferidos para eguas receptoras aciclicas, tratadas com altrenogest. Vinte e quatro receptoras gestantes por transferencia de embriao durante a fase ciclica (grupo Controle; n=8) ou aciclica (grupo Altrenogest; n=16) foram avaliadas por meio de ultrassonografia transretal, a cada cinco dias, para monitorar o desenvolvimento da vesicula embrionaria entre 15 e 45 dias de gestacao e embriao/feto dos 20 aos 60 dias. As caracteristicas da vesicula embrionaria quanto ao formato, localizacao do embriao dentro da vesicula e formacao do cordao umbilical foram similares em receptoras ciclicas e aciclicas. O crescimento da vesicula embrionaria e embriao/feto foi significativo (P0,05). O crescimento da vesicula embrionaria e embriao/feto tambem foi similar (P>0,05) entre grupos nos diferentes dias de gestacao. A similaridade no crescimento do concepto entre eguas receptora