Oestrus synchronization efficiency in ewes and ram maturity effect on fertility during summer season

The purpose of this study was to investigate oestrus synchronization efficiency and ram maturity effect on fertility of ewes of MIS sheep population during summer season. Research was performed on the experimental sheep farm of the Institute for Animal Husbandry in Belgrade, Serbia. The study included 70 crossbred ewes of MIS sheep population (Pirot Pramenka, Merinolandschaf and Ile de France breed) and 3 Ile de France rams (2 young, sexually unexperienced rams and 1 mature ram). Oestrus was synchronized in all 70 ewes using progestagen impregnated vaginal sponges (30 mg fluorogestone acetate) in combination with 500 IU PMSG. Ewes were mated with rams 48 h later. Obtained fertility and productivity results were as follows: lambing rate 57.14% (40/70), gestation length 147.11, litter size 1.82, stillborn rate 15.07%, birth weight of lambs 4.29 kg and body weight of lambs at 30 days of age 13.07 kg on average. Based on the results obtained in this study it was concluded that presented oestrus synchronization and mating protocol yielded lower than expected lambing rate. The effect of ram maturity on lambing rate was significant (P<0.05), as ewes mated to mature ram had higher lambing rate compared to those mated to two young unexperienced rams. Mature ram also had bigger litter size and higher stillborn rate, as well as lower birth weight of lambs.