Utilization of barley straw, chemically treated with ammonium sulfite, anhydrous ammonia or urea, by ruminants

Abstract

Straw treated with anhydrous ammonia, ammonium sulfite, urea or left untreated was examined in a series of feeding experiments to determine the relative efficacy of the treatments to improve the nutritive value of barley straw. In exp. 1, diets containing ammonia- and ammonium sulfite-treated barley straw were more digestible (P < 0.05) than diets with untreated straw. In exp. 2, average daily gain (ADG) and voluntary feed intake (VFI) were greatest for heifers fed ammonia-treated straw, followed by heifers fed urea-treated straw, and then by heifers fed ammonium sulfite-treated straw. Heifers fed untreated straw had the lowest ADG and VFI (P < 0.05). Although ammonium sulfite treatment improved straw digestibility, the relatively low VFI resulted in ADG lower than for animals fed other treated straw. The low VFI was attributed to the high level of sulfur in the diet. Anhydrous ammonia and urea were found to be the most effective chemicals for improving the nutritive value of barley straw. Although ammonium sulfite was as effective an anhydrous ammonia in improving digestibility of straw, it cannot be recommended because the application rates, necessary for effective treatment, resulted in depressed feed intake. Key words: Urea, anhydrous ammonia, ammonium sulfite, straw, digestibility, cattle