Fourty ewes (½ Finnish Landrace - ½ Rahmani) were used. Animals were divided into 4 groups, 10 ewes each. Ewes of the 1st group (G1, control) were bred naturally while those of the other three groups (G2, G3 and G4) undergun hormone treatment and were artificially inseminated. Ewes in G2 were i.m. injected with 4 mg Buserelin (day 0), 175 mg cloprostenol (day 7) and 4 mg Buserelin (day 9), and artificially inseminated 24 h later. Ewes in G3 were intravaginally treated with 45 mg FGA impregnated sponge for 11 days. Ewes in G4 were intravaginally treated (day 0) with Control Internal Drug Release (CIDR) for 11 days. Animals in G3 and G4 were i.m. injected with 600 IU PMSG 48 h before and 175 mg cloprostenol (day 11) at device withdrawal, then artificially inseminated 52 h later.
Results showed that occurrence of oestrus was 30% in G2 and 100% in each of G3 and G4. Oestrus occurred (in average) earlier after end of treatment in G3 than in G2 and G4. Estrous duration was similar in the three treatment groups. Lambing rate was similar between control, G3 and G4 (70% in each) and was significantly (P<0.05) higher than in G2 (50%).
It was concluded that synchronization of oestrus in ewes by applying controlled FGA or CIDR plus PMSG and PGF2a might be a possibility to attain synchronized and early lambings in fall, to maximize the economic return.