Comparison of lupin varieties for nutritive value as dry standing feed for weaner sheep and for incidence of lupinosis

Abstract

Several lupin varieties were grown on sandy and sandy gravelly soils in a Mediterranean environment. During the three years when they were grown, the rainfall varied from 400 to 700 mm. The yields of dry matter and grain for the cultivars Borre, New Zealand Blue, Uniwhite and Uniharvest of L. angustifolius were not significantly higher than those of the Chapman cultivar of L. cosentinii and the Weiko III cultivar of L. luteus. However, more blocks of these last two cultivars failed owing to weed competition. The nitrogen, phosphorus, sulphur, sodium, neutral detergent fibre and water-soluble carbohydrate contents of the stem, leaf, pod and seed at maturity did not differ greatly between varieties within years.

Weaner Merino shcep grazed at 50 sheep ha^-1 on these standing dry crops gained up to 10 kg in 80 days. Sheep weight gains over three years were consistently the best for sheep on Borre, Uniwhite and Uniharvest; sheep on Chapman lupins gained little weight in any year, whilst Weiko III gave intermediate gains in one year and poor gains in another. The differences in weight gain were associated in all years with differences in the initial amounts of grain present.

Detailed nutritional studies on sheep in the first year showed that the nutritive values of the varieties not causing lupinosis were similar in terms of digestible organic matter intake, volatile fatty acid production and proportions, and blood urea concentration.

Abnormal liver metabolism, inferred from the level of ornithine carbamoyl transferase in the blood, occurred in sheep on all varieties during the three years, and lupinosis was confirmed by necropsy in two of the years. Lupinosis resulted in nine deaths out of 250 sheep, but other sheep with liver damage achieved normal liveweight performance. In each year, liver damage occurred on dry lupins before any summer rain. There was a high incidence of lesions of the fungus Phomopsis rossiana on stems of the cultivars Chapman and Weiko III during growth. The presence of lesions at this stage appeared to be more closely associated with the occurrence of lupinosis in summer than with the incidence of Phomopsis infection on dry sterns following summer rains.