Immunisation against ovarian steroids has been shown to improve the reproductive performance of ewes. Using this principle the drug Fecundin was developed by Glaxo Animal Health Ltd. and is marketed by Coopers Animal Health Ltd. who supplied the drug for this study. The response to Fecundin was evaluated in ewes lambing in the spring under a wide range of commercial conditions in an ADAS co-ordinated trial.

ADAS Sheep Specialists and Advisers co-operated in locating and collecting the data from suitable commercial flocks and 2 EHF's with a minimum of 150 but more usually 200 ewes and where accurate lambing records could be obtained. Potentially naturally prolific types of ewes eg. Mules and Finn crosses were excluded. Approximately eight weeks before the rams were introduced all the ewes were condition scored and randomised to treatment or control. Treated ewes were injected with Fecundin and again 21-28 days later. At lambing the number of lambs born alive and dead and barren ewes were recorded in all flocks. Lambing dates, lamb birthweights and lamb survival were available in a limited number of flocks.