Oestrous synchronisation and twinning rate of Syrian Awassi ewes treated with progestagen and PMSG during the breeding season

Abstract

An experiment was conducted on Awassi ewes, during the breeding season, to evaluate the effectiveness of intravaginal sponges for oestrous synchronisation and the effect of pregnant mare serum gonadotropin (PMSG) on twinning rate. Thirty intact ewes with an average live weight of 3.1 ± 9.1 kg were divided into 3 equal groups. Sponges containing 60 mg of medroxy‐progesterone acetate (MAP) were inserted for 13 days in ewes in groups Tl and T2. Ewes in the latter group (T2) were injected intramuscularly, at the time of sponge withdrawal, with 500 i.u. of PMSG. The third group (C), received no treatment and served as a control. The mean interval to onset of oestrus was 2.0 days (range: 1.2–3.0 days) and 2.1 days (range: 1.0–3.9 days) after sponge withdrawal for ewes in groups Tl and T2, respectively (P > 0.05). In the control group (C), time of onset of oestrus was more variable (mean: 4.2 days, range: 1–14 days). Differences between the treated and the control animals in the time of onset of oestrus were significant (P < 0.05). The mean concentration of progesterone at sponge withdrawal was 0.16 and 0.08 and at mating was 0.11 and 0.10 nmol 1‐1 for groups T1 and T2, respectively. The treatments had no effect on duration of pregnancy, lamb birth weight, or lamb weaning weight. Using PMSG at sponge withdrawal increased twinning rate from 20% in groups T1 and C to 50% in group T2. It is concluded that intravaginal sponges (MAP) can be used for oestrous synchronisation in local Awassi ewes during the breeding season and that treatment with PMSG at the end of MAP treatment increases twinning rate.