There is increasing interest in the development of systems in which crossbred ewes are lambed later in the spring so that the ewes’ nutritional needs are matched more closely with grass growth (Stone, 1988). Lambs may then be sold as stores in the autumn or finished indoors on silage-based diets through the winter (Povey and Webster, 1987). However, ovulation rate tends to be declining at the time of mating in such a system. These experiments were designed to investigate the benefits of using Fecundin, either alone or in conjunction with pregnant mares’ serum gonadotrophin (PMSG) in synchronized ewes lambing in April/May.

Two groups of 30 Mule (Bluefaced Leicester x Swaledale) ewes matched for age, weight and condition score were allocated to the experiment. Treated ewes were given 2 x 2 ml intramuscular (i.m.) injections of Fecundin®(Coopers Animal Health) four weeks apart while control ewes received no Fecundin treatment. Unfortunately a ram escaped into the flock prior to the planned mating date. All ewes were therefore injected i.m. with 1.5 ml Lutalyse®(Upjohn) 12-16 days after suspected mating. However, it would appear that the dose used was insufficient to cause abortion and only those ewes marked subsequently by a raddled vasectomized ram remained in the experiment. All these ewes (n = 17 per group) were treated with progestagen-impregnated intravaginal sponges (Veramix® Upjohn) left in situ for 12 days. Rams were introduced on 18th December 1986, two days after sponge withdrawal and four weeks after the second injection of Fecundin. The ewes were shorn and housed prior to ram introduction and given a diet of hay ad libitum with up to 1 kg concentrates by the time of lambing in May 1987.