Universidad y ciencia
Print version ISSN 0186-2979
MARTINEZ-TINAJERO, JJ et al. Reproductive performance of F1 (Damara x Merino) ewes synchronised with CIDR and two times of GnRH injection. Universidad y ciencia [online]. 2008, vol.24, n.3, pp. 175-182. ISSN 0186-2979.
The experiment was carried out to evaluate the reproductive performance of F1 (Damara x Merino) ewes imported from Australia, synchronised with controlled internal drugs (CIDR) and two times of injection of gonadotropin releasing hormone (GnRH). Forty five F1 ewes at first lambing, of 18.08 ± .07 months of age and 43.3 ± 5.6 kg of body weight were randomly assigned to one of three treatments: T1 (n = 15): CIDR for 12 days; T2 (n = 15): CIDR for 12 days plus 25 μg of GnRH 48 h before CIDR withdrawal and T3 (n = 15): CIDR for 12 days plus 25 μg of GnRH at the moment of CIDR withdrawal. The percentage of estrus presentation (100%) was similar (p > 0.05) for T1, T2 and T3. The interval (h) of the onset of synchronised estrus after CIDR removal was different (p <0.05) for T2 and T3 (43.8 ± 5.4 and 45.7 ± 3.3 h) compared with T1 (37.3 ± 7.9 h). The percentage of fertility at the synchronised estrus was similar (p > 0.05) for T1, T2 and T3 (60.0, 53.3 y 46.6%, respectively). The general average prolificacy was 100.8% and similar (p > 0.05) among treatments. The concentration of progesterone insured that the tested ewes had a functional corpus luteum at the beginning of the experiment. It is concluded that the combined use of CIDR and GnRH, 48 h before and at the moment of CIDR removal, has no effect on the reproductive performance of F1 (Damara x Merino) ewes.
Keywords : CIDR; GnRH; reproduction; estrus synchronisation; progesterone; ewes.