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FACTORS AFFECTING LITTER SIZE IN THE SCOTCH HALF-BRED EWE

Summary.: Ninety-eight ewes were injected with pregnant mare serum gonadotrophin (PMSG) during the normal breeding season. Injections of 1250, 1500 and 2000 i.u. of PMSG were given on the 12th or 13th day of the oestrous cycle. This resulted in 2·61, 2·81 and 2·44 lambs/ewe, respectively.

One hundred and eleven ewes were treated with Syncromate to synchronize oestrus during the normal breeding season. A PMSG injection was given 14 days after pessary removal. Eighty-three ewes conceived to the first oestrus following injection with 1500 i.u. PMSG, and produced, on average, 2·49 lambs each. One ram gave rise to more lambs per ewe. Eighteen ewes were barren.