Productivity of ewes grazing lupin stubbles at mating in north-eastern Victoria

The liveweight gains, lambing performances and wool production of Border Leicester x Merino ewes grazed on sweet narrow-leafed lupin (Lupinus angustifolius) stubbles during mating in midsummer were compared with those grazed on annual pasture. Treatments and conditions varied during the 5 years of study. In years 1-3, the stubbles were stocked at rates of between 20 and 40/ha, in year 4, at 11 ewes/ha, and in year 5 at 24 ewes/ha. In the last year there was an additional pasture treatment when the ewes on dry pasture were divided, one half were given 400 g lupin grain/sheep daily and the remainder, none. Available dry matter on the pastures varied from 1.1 to 5.0 t/ha and lupin grain in the stubbles varied from 230 to 420 kg/ha. Vasectomised rams were joined with the ewes 1 week before they were put onto the lupin stubbles and, after 2 weeks, were exchanged for entire rams which remained with ewes for 17-33 days. As the stocking rates on stubbles increased there were decreases in liveweight gains, ewes lambing and lambs born per ewe joined. During the 5 years, ewes grazed on stubbles at less than 25/ha gained more weight (176 g/day more), had more lambs (0<26/ewe mated), while more of them lambed (0.07/ewe mated) than did ewes on pasture alone (P < 0.05). The ewes fed lupin grain at pasture in year 5 received less grain than those on the stubbles and their production was intermediate to those on pasture alone and stubbles. At the lowest stocking rate of ewes grazing stubbles (20/ha) average wool production increased by about 37% (years 2-3) and 58% (year 5) compared with ewes grazing pasture. We conclude that lambing percentages from a midsummer mating can be increased when crossbred ewes graze sweet lupin stubbles during mating.