Effect of rbst treatmen on productive and reproductive performance of ewes

This study was carried out at Sakha Animal Production Research Station, belonging to Animal Production Research Institute, Agricultural Research Center, Ministry of Agriculture. The current work aimed to study the effect of rbST treatment during pre- and postpartum period on live body weight, milk production, composition and lambing rates of crossbred ewes (1/2 Finnish Landrace x 1/2 Rahmani). A total number of 40 mature healthy crossbred ewes (1/2 Finnish Landrace x 1/2 Rahmani) having 3-4 years of age were divided into two similar groups (control and treatment), according to their live body weight (LBW). Ewes in the first group were served as a control group, while those in the second group were treated with a subcutaneous injection of 160 mg recombinant bovine Somatotropin (rbST) at 14-day interval during one-month prepartum and 4 months postpartum. During May mating season, ewes were monitored for sign of oestrus and those observed in heat were natural mating using 4 fertile rams. Milk yield and composition were determined throughout first 8 lactation weeks. Results show that LBW of ewes at prepartum and early postpartum suckling period was not affected by rbST treatment. However, treated ewes were heavier (P0.05) by about 5% than controls only during late postpartum (breeding season from April to June). Treatment with rbST increased (P0.05) average daily milk yield of ewes during the 1st eight weeks of lactation. The magnitude of increase ranged between 16 and 33% during different lactation weeks. Treatment with rbST decreased (P0.05) contents of fat, protein and in turn total solids in milk of ewes during the first 2 months of lactation. However, lactose and ash contents in milk of ewes were not affected significantly by rbST treatment. Treatment with rbST increased (P0.05) oestrus/mating rate (40 vs. 70%) and reduced postpartum period of lambing ewes by about one month as compared to untreated ewes (65 vs. 93 days). Lambing rate based on number of mated ewes was significantly (P0.05) lower in control than in treated ewes (75 vs. 85.7%). In conclusion, injection of 160 mg rbST at 14-day interval during one-month prepartum and 4 months postpartum improved milk yield and lambing rate of ewes