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INDUCTION OF FERTILE OESTRUS IN PREPUBERTAL EWES DURING THE ANOESTROUS SEASON

Induction of fertile oestrus during the anoestrous season in mature lactating and dry ewes is possible with the proper sequence of hormone treatments. Wagner (1964) found 0·5 or 1·0 mg of 6-chloro-6-dehydro-17 acetoxyprogesterone (CAP) per head per day in the feed for 16 days and 1000 i.u. pregnant mare's serum gonadotrophin (PMSG) injected 36 hr and 18 days later to be effective in producing fertile matings. The best regimen resulted in 77% of the treated ewes lambing. Hansel (1964) observed that treating lactating Western White-faced ewes with 750 i.u. of PMSG on Days 1 and 15 and feeding 60 mg of 6-methyl-17-acetoxyprogesterone (MAP) daily from Days 7 to 14 resulted in 65% of the treated ewes lambing. Hulet & Foote (1967), testing various combinations of CAP, MAP and PMSG on dry and