USO DEL PROTOCOLO OVSYNCH EN EL CONTROL DEL ANESTRO POSTPARTO EN VACAS MESTIZAS DE DOBLE PROPÓSITO Using of Ovsynch Protocol in Anoestrus Control in Dual Purpose Crossbred Cows

In order to evaluate fertility parameters using the Ovsynch proto- col in crossbred dual purpose cows, and to determine optimum time for timed-AI (IATF), 37 out of 48 noncycling cows were as- signed to different groups: T1: day 0: GnRH; day 7: PGF2 day 9: GnRH (Ovsynch) + IATF 24 h post-last injection of GnRH, (n = 14); T2: Ovsynch + IATF 16 h post-last injection of GnRH, (n = 11); C: control, (n = 12). Studied variables were: Early Estrus Rate (EP), Conception Rate (TC), Pregnancy Rate (TP) and In- terval between Treatment and Pregnancy (ITP). Variables EP, TC y TP were evaluated using the SAS FREQ procedure while ITP was analyzed using the SAS GLM procedure. The EP rate was higher (P<0.05) for T (30.5%, 11/36) vs C (8.3%, 1/12). The TC was similar between CP (72.7%, 8/11) and T1 (42.8%, 6/14); but TC was higher for T1 (P=0.06) than T2 (42.8%, 6/14 vs 9.1% 1/11). No differences in TP were found between T1 and T2 (50%, 7/14 vs 45.5%, 5/11), but both groups had a higher TP when compared to C (25%, 3/12) (P<0.05). The ITP was shorter (P<0.05) in T1 (38.9 + 15.7 dias) compared to T2 and C (62.4 + 18.8 days and 60.0 + 35.1 days, respectively). In conclusion, IATF 24 h post GnRH resulted in a higher TC and shorter ITP when used in conjuction with the Ovsynch treatment. The Ovsynch protocol presents analternative for postpartum anes- trus control and improves the reproductive efficiency in produc- tion systems using dual purpose cows.