Maintenance of oestrus synchronisation in two-year-old ewes at second heat after progestagen sponge treatment

Abstract

Romney and Border-Romney maiden 2-year-old ewes were treated for 14 days with intravaginal progestagen sponges at the start of the breeding season. After sponge withdrawal and at the next cycle 80% and 90% respectively of all ewes were in oestrus, and of these 77% and 80% were marked over 2 and 3 days respectively. Pregnant mare's serum gonadotrophin (PMSG) (600, 1200 i.u.) injected on day 12 or 13 after first heat did not affect synchronisation of oestrus, although the mean onset of oestrus was earlier than in control ewes. Improved nutrition, treatment with PMSG, and injection on day 12 reduced mean cycle length.