Supplementing Merino ewes at mating for reproductive gain in central western New South Wales

Abstract

In four experiments at Condobolin on the Central Western slopes of New South Wales between 1976 and 1979, mature Merino ewes were given supplements for four to five weeks over mating and the effects on their reproductive performance were recorded. The ewes were run on barrel medic or native pasture with mating commencing in late February or early March each year. The supplements were: experiment 1 -1upins (0.25 kg/d), oats (0.25 kg/d); experiment 2-lupins (0.25 kg/d), oats (0.25 kg/d); experiment 3-lupins (0 25 kg/d), lupins (ad libitum), lupins (0.25 kg/d) with ad libitum oats and lucerne hay; experiment 4-lupins (0.25 kg/d). In experiment 4, ewe liveweight was manipulated in the pre-feeding period to obtain two liveweight classes at the start of supplementation. In the three to four weeks before mating, ewes either maintained or lost weight in experiments 1,2 and 4. However, in experiment 3, ewe liveweight increased after heavy summer rains caused an abundance of pasture. The only significant effect of any supplement on flock reproduction was to increase the ovulation rate. This resulted from lupin supplementation but only in two of four years (experiments 1 and 4). However, on these occasions, lambing rates did not significantly increase due to three factors: more barren ewes, higher ova loss or greater peri-natal lamb loss. Oats supplementation in experiments 1 and 2 did not significantly increase reproductive performance, nor was there an effect of any supplement in experiment 3. The results indicate that repeatable reproductive responses to lupin supplementation are unlikely to occur in the area of the study.