Nutritive value of alkali-treated wheaten straw fed to sheep with supplements of either lupins or barley and urea

Abstract

Untreated straw and alkali-treated straw were prepared by spraying long wheaten straw in windrows with water or a 6.6% (w/v) solution of sodium hydroxide to give a concentration of sodium hydroxide of 7g per 100 g straw. Merino wethers were fed the straws ad libitum with or without a supplement of either lupins or a mixture of barley and urea. The in vivo organic matter digestibilities (%) of the alkali-treated straw diets supplemented with lupins (61.3) or barley and urea (59.3) were greater (P<0.05) than those of the untreated straw diets supplemented with lupins (54.6) or barley and urea (55.7). The intakes of dry matter (g day-1) and digestible energy (MJ day-1), respectively, were greater (P<0.01) for the sheep offered alkali-treated straw supplemented with lupins (769, 7.7) or barley and urea (847,7.9) than for those offered untreated straw supplemented with lupins (598, 5.4) or barley and urea (639, 5.9). Sheep offered the supplemented alkali-treated straw diets produced 39% more wool and lost less (P<0.05) liveweight than sheep offered the supplemented untreated straw diets. Retention of nitrogen (g day-1) by sheep was greater (P<0.01) when the alkali-treated and untreated straws, respectively, were supplemented with barley and urea (3.6, 2.8) than with lupins (1-9, 0.9). It is concluded that a more effective method of application of sodium hydroxide must be developed if treatment of straw with sodium hydroxide is to become a routine and economic technique for use on southern Australian farms.