Monitoring the reproductive performance in awassi ewes using progesterone radioimmunoassay

Jugular serum progesterone (P-4) concentrations were assessed using radioimmunoassay (RIA) kits for about 1 year in 16 local Awassi ewes aged about 1 year and weighing on average 37.4 ±4.9 (range 29.5-44.0 kg). Average pre-mating live weight of animals was different (P<0.05) between animals and was 55.4±4.7 (range 46.5-64.5 kg). There were no statistical differences (P>0.05) between animals in average basal pre-mating P-4 concentration, maximum P-4 concentration during the luteal phase in non-pregnant ewes and in the length of the gestation period average basal pre-mating P-4 concentration was 0.62±0.44 (range 0-1.7 nmol l-1). Average maximum P-4 concentration during the luteal phase in non-pregnant ewes was 11.0±3.3 (range 5.8-18 nmol l-1). Length of gestation period varied from 149 to 155 days with an average of 152±2.3 days. Maximum P-4 concentration during gestation was different (P<0.05) between animals averaging 58.4±20.9 (range 29.25-100 nmol l-1). The accuracy of pregnancy diagnosis at around 21 days pot-mating using RIA was 100%. It was concluded that Awassi sheep in Syria have a long breeding season that could start as early as April and last through September. Therefore, ewes might be included in oestrous synchronisation programmes to give three lambs in 2 years. It was also concluded that P-4 concentration under 3.18 nmol l-1 is indicative of either anoestrous or follicular and early luteal phase of the oestrous cycle in Awassi ewes kept in Syria and that RIA could be used for P-4 determination and successful early diagnosis of pregnancy in Awassi sheep. (author)