THE EFFECT OF FEEDING DIETS CONTAINING INTACT OR PARTIALLY DETOXIFIEDLUPIN ON VOLUNTARY INTAKE AND MILK-PRODUCTION BY FRIESIAN DAIRY-COWS

The study determined the effects of partial removal of alkaloids (deto xification) in crushed lupin seed (CLS) on voluntary food intake, and yield and composition of milk from dairy cattle. Twenty multiparous Fr iesian dairy cows (first 90 days of lactation) were assigned, accordin g to a randomized complete-block design, to five diets. The diets were formulated to be isonitrogenous (25.6 g N per kg of diet dry matter ( DM)) and contained napier grass, lucerne hay, maize bran and urea. The control diet (CON) contained sunflower meal; two diets contained inta ct CLS at 150 (LUI-15) or 300 g (LUI-30) per kg diet DM. The other two diets contained detoxified CLS at 150 (LUD-15) or 300 g (LUD-30) per kg diet DM. Lupin seeds were detoxified by treatment with boiling wate r, followed by steeping in cold water. The diets were analysed by gas chromatography for the alkaloids, lupanine and 13-hydroxylupanine. The total alkaloid content of LUI-15 and LUI-30 was 3.8 and 8.0 g/kg diet DM, respectively; by contrast that of LUD-15 and LUD-30 was 2.1 and 5 .2 g/kg diet DM respectively. Increasing the level of intact CLS in th e diet led to a decrease in voluntary food intake. Cows given LUI-30 h ad a lower milk yield (11.1 kg/day) than those given LUI-15 (13.8 kg/d ay; P < 0.01) but there was no difference in either milk protein yield or content. Detoxification of lupin removed proportionately about 0.4 0 of the total alkaloids from intact CLS and increased food intake, an d the yield of milk and milk protein (P < 0.05) but reduced milk fat c ontent. Detoxification of CLS also reduced the rumen degradability of lupin protein (P < 0.05). It is concluded that the reduction in organi c matter intake and milk yield of cows given diets containing intact C LS was due to the presence of lupanine and 13-hydroxylupanine. To maxi mize its usage in diets for dairy cattle, lupin should be detoxified i t can then be included at levels up to 300 g/kg diet DM.