Abstract:
Proc. Aust. Soc. Anim. Prod., Vol. 17 SURVIVAL OF OVA IN EWES GIVEN DIFFERENT MEANS OF OVARIAN STIMULATION J.F. WILKINS* and D.R. LINDSAY* 481 There are now many ways of increasing ovulation rate in ewes, but little is understood of their effects on the survival of extra ova produced. To examine this, 558 Merino ewes were randomly allocated to a control group (C) or one of three stimulation treatments. The first treatment (L) was a lupin grain supplement of 750 g/hd/d given nine, eight, six, four and one days before introduction of the rams. Ewes in the second treatment (F) were given injections of Fecundin (Glaxo) at seven and four weeks before mating. In the third treatment (N) ewes were given an 'improved nutrition' supplement of barley grain and ad lib. pasture hay. Grain was introduced at 100 g/hd/d at six weeks, progressing to full ration of 750 g/hd/d for four weeks prior to mating. All ewes were supplemented with 400 g/hd/d barley grain and limited hay from mating until mid-pregnancy. Ewes were synchronised with progestagen sponges (60 mg Repromap, Upjohn) and 'teaser' wethers introduced at sponge withdrawal. Mating with 35 entire rams commenced on 2/3/87, at the second synchronised cycle. Rams were removed after five days in the first mating cycle and reintroduced 12 days later. Ewes were run and mated together except for the times required by treatment. We examined all ewes by laparoscopy at 510 days after mating and by ultrasound imaging at 26-30 and 76-80 days. TABLE 1 Reproductive performance in the first cycle for ewes given three treatments to increase ovulation rate Treatment group C L F N Ovulation rates in treated ewes were greater than in controls and differed between groups. Treatment effects on proportions of ewes pregnant and survival of ova were consistent, with Group L performing the best in all aspects and Group F mostly the worst. Survival of single ova in Group F was particularly low. Within all groups, two ova shed from the one ovary had lower survival rates than those shed from different ovaries. This was also noted by White et al. (1981). The proportion of extra lambs produced from extra ova shed, comparing treated groups with the control, clearly ranked lupin supplement as the most 'efficient' treatment. WHITE, D.H., RIZZOLI, D.J. and CUMMING, I.A. (1981). Aust. J. Exp. Agric. Anim. Husb. 21: 32. Supported by A.M.L.R.D.C. *School of Agriculture (Animal Science), University of WA, Nedlands WA 6009