Characterization of certain reproductive parameters in Syrian female awassi sheep during different stages

Two experiment were conducted on Syria female Awassi sheep to characterize some reproductive parameters during different reproductive stages. In the first experiment, 18 ewe lambs at 5 months of age were tested for a period extending for 16 months. The overall average age at puberty, as indicated by the sharp increase in progesterone concentration followed by regular oestrous cycles, was 18.0 ± 1.1 months (15.7-19.9 months), occurring between May and August (during the normal breeding season). There were no significant differences in the time to attain puberty among the ewe lambs in terms of their months of lambing, type of birth (singles or twins) of weaning weight. The average live weight of ewe lambs at the age of 5 months was 24.6 ± 4.6 kg, and at the attainment of puberty 53.7 ± 7.2 kg, while the average serum progesterone concentration at the age of 5 months was 0.27 ± 0.26 nmol l-1, and at the attainment of puberty 6.32 ± 3.69 nmol l-1. In the second experiment, 16 of the ewe lambs utilised in the first experiment were used at an age of 21 months for a period lasting for an additional 8 months. Female animals were divided, during the breeding season, into 2 equal groups, experimental (P) and control (C). All animals in both groups were treated with intravaginal sponges containing 40 mg of flugestone acetate (FGA) for a period of 14 days. However, only females in the P group were injected intramuscularly, at the sponge withdrawal, with 500 I of pregnant mare serum gonadotropin (PMSG). Three fertile Awassi rams were introduced into both groups after 24 hours of sponge withdrawal for oestrus detection and mating. All the females exhibited oestrus and were mated within 3 days after sponge withdrawal. The twinning percentage was 37.5% in the females that were injected with PMSG as compared to 12.5% in the females that were not injected. It was concluded that Syrian Awassi ewe lams attain puberty during the second breeding season of their life at an age of about 18 months and at an average live weight of around 54 kg at which they become capable of reproduction. In addition, no effects were observed for the month of lambing, birth weight or weaning weight of lams on the time to attain puberty. It was also concluded that it is possible to improve the twining percentage of the animals in their first pregnancy using PMSG without an adverse effects on either the lamed ewes or the born lambs. (author)