Abstract:
proc. Aust. Soc. Anim. Prod. Vol. 18 REPRODUCTIVE WASTAGE IN SOUTH AUSTRALIAN COMMERCIAL MERINO FLOCKS D.O. KLEEMEN*, S.K. WALKER*, T.I. GROSSER*, R.J. GRIMSON* and D.H. SMITH* Reproductive performance of the Australian Merino remains poor with little In South increase in lamb marking percentage over the last three decades. A u s t r a l i a , lamb marking percentage has remained virtually static, and averages To define the problem, we only 77 lambs marked per 100 ewes joined. investigated the sources of reproductive loss in South Australian commercial Merino flocks grazed in different agricultural regions of the State. In the first year of a three-year study, 10 flocks of 300-400 mature-aged Merino ewes were selected from different properties on the basis of rainfall isohyet (3000406, >400-500, ~500 mm), time of joining and lamb marking percentage. Ovulation rate (OR) of each flock was estimated from 75-90 ewes by laparoscopy. The number of foetuses present during mid-pregnancy was evaluated by real-time ultrasound imaging, and the number of lambs and ewes present at marking was recorded. Table 1 Reproductive performance of ten S.A. commercial Merino flocks Potential reproductive performance (OR) was higher than that observed in Western Australia (135 v 114) (Lindsay et al, 1975). Our result for lamb marking percentage was high compared with the State average (89 v 77) and is probably a reflection of good seasonal conditions and exclusion of maiden ewes from our study. The sources of reproductive wastage were shared equally between those occurring during pregnancy and those occurring during and shortly Sampling of further flocks is required to obtain a reasonable after lambing. estimate of the sources of reproductive loss in commercial Merino flocks in South Australia. LINDSAY, D-R., KNIGHT, T-W., SMITH, J-F. and OLDEXAM, GM. Agric. Res. 26:189. (1975). Aust. J. *- Turretfield Research Centre, Rosedale, S.A. 5350. 504
