Synchronisation of oestrus in the S.A. Mutton Merino: the influence on conception and fecundity:

During the breeding season 183 South African Mutton Merino ewes were used to study the effect of MAP + PMSG on conception and fecundity. With an increase in PMSG level from 300 to 600 IU conception rate decreased by 19,2 per cent (P < 0,05), while mortality in new-born lambs increased by 15,3 per cent (P < 0,05). For the same number of ewes lambed, the ewes in the group receiving 600 IU produced significantly (P < 0,0l) more lambs dead and alive, than both for the control group and these ewes treated at the lower dose level and in the latter group 53 per cent of the ewes produced twins and 7 per cent triplets compared to the 30 per cent twins, 31 per cent triplets and 17 per cent quadruplet and quintriplet at the 600 IV level. By increasing the PMSG level from 0 to 300 IV, twin births did not increase, but conception rate as well as lambing percentage improved considerably.