Inseminación artificial a tiempo fijo con semen ovino refrigerado

espanolSe evaluo la prenez resultante de la inseminacion artificial sistematica cervical (IASC) con semen ovino refrigerado a 5°C durante 12 o 24 h y dosis de 150 o 300 millones de espermatozoides. Doscientas ovejas adultas Merino se dividieron al azar en grupos de 40 animales, segun arreglo factorial de los tratamientos (2x2) mas un grupo control. En la estacion reproductiva, los estros fueron sincronizados mediante 14 dias con esponjas intravaginales con 60 mg acetato de medroxiprogesterona y 200 UI de eCG al retirar las esponjas. A las 12 y 24 h previas a la IASC se colectaron, diluyeron y refrigeraron los eyacu-lados. La dilucion del semen se realizo con OviPro (Minitub®, Alemania) en una relacion 1:2 (semen/diluyente). El grupo control fue inseminado con semen fresco sin diluir y dosis de 100 millones de espermatozoides. La IASC se realizo en el orificio uterino externo a las 54-56 h despues del tratamiento progestacional. La preservacion seminal durante 12 h alcanzo el 25% (10/40) y 38% (15/39) de prenez con dosis de 150 y 300 millones de espermatozoides. El semen preservado durante 24 h determino el 3% (1/37) y 19% (7/37) de prenez con dosis inseminantes de 150 y 300 millones de espermatozoides, respectivamente. El porcentaje de prenez del grupo control (59%) evidencio que las condiciones de la majada no estuvieron afectadas por el estado nutricional o de manejo. La IASC con semen refrigerado ovino durante 12 h y una dosis de inseminacion de 300 millones de espermatozoides, permitio obtener una prenez aceptable (38%) considerando el beneficio de poder transportar semen a largas distancias y su bajo costo operativo. EnglishWe evaluated pregnancy by timed artificial insemination (TAI) with ram semen chilled at 5oC during 12 or 24 h and insemination doses of 150 or 300 millions spermatozoa. Two hundred adult Merino sheep were randomly divided in 4 groups of 40 animals each, according to a factorial arrangement (2x2) plus a control group. During the breeding season, estrus were synchronized with intravaginal sponges impregnated with 60 mg of medroxyprogesterone acetate inserted for 14 days and administration of 200 UI PMSG at sponge removal. Twelve and 24 h before insemination, semen from adult Merino rams was collected, and after the ejaculates were diluted and chilled. Semen was diluted with the Ovipro extender (Minitub®, Alemania) using a dilution rate of 1:2 (semen/extender). Control group was inseminated with fresh semen without diluent and an insemination dose of 100 millions spermatozoa. For every group, cervical TAI was performed 54-56 hours after progestational treatment. Preserved semen during 12 hours obtained 25% and 38% pregnancy with an insemination dose of 150 and 300 millions spermatozoa. Semen preserved for 24 hours caused 3% and 19% pregnancy with an insemination dose of 150 and 300 millions spermatozoa respectively. Control group showed a pregnancy of 59%, which evidenced that flock fertility was not affected by nutritional status or management. TAI with ram chilled semen during 12 h, with an insemination dose of 300 millions spermatozoa, was found to provide an acceptable fertility (38%), considering the benefit of carryng semen for long distances and the low operative cost for its implementation.