ABSTRACT
Effect of time of artificial insemination after estrus detection on Corriedale sheep pregnancy rates

Camila Muñoz M.1*, Víctor H. Parraguez G.2 y Etel Latorre V.3
 

A total of 240 adult Corriedale ewes from the Magallanes Region of Chile, were synchronized with progestagens and randomly assigned to one of four groups, according to the time elapsed between estrus detection and artificial insemination (AI) with semen obtained from 2 Corriedale rams. The first three groups were inseminated at 3 and 6; 6 and 12; or 12 and 18 h after estrous detection; the fourth group received a single insemination 18 h after estrous detection. Semen was extracted and frozen in a solution of skimmed milk, glycerol and egg yolk, thawed and used, registering the depth of semen placement in the cervix and the quantity and nature of the cervical mucosa. Pregnancy was assessed by ultrasound 30 days after insemination. No significant statistical differences were detected among pregnancy rates, which were 22; 31; 22; and 21% for groups 1; 2; 3 and 4, respectively. Nor were there significant differences with one or two inseminations. Results showed that fertility did not differ when insemination was performed 3 to 18 h after estrous detection, and that double insemination is not necessary, as long as insemination coincides with the middle of the estrous period.

Keywords: artificial insemination, frozen semen, intracervical insemination.
1 Instituto de Investigaciones Agropecuarias, Centro Experimental Rayentue, España 512, 2º piso, San Fernando, Chile. E-mail: cmuñoz@rayentue.inia.cl * Autora para correspondencia.
2 Universidad de Chile, Facultad de Ciencias Veterinarias y Pecuarias, Casilla 2 - Correo 15, La Granja, Santiago, Chile. E-mail: vparragu@uchile.cl
3 Instituto de Investigaciones Agropecuarias, Centro Regional de Investigación.