High-molasses diets for intensive feeding of cattle

Abstract

Northern Australian production of molasses usually exceeds 1 million tonnes per year. Over half of this is exported, mostly from sugar mills in the far north. The establishment of a feedlot industry in northern Australia, based on molasses being the major energy-dense component of diets, is dependent on the formulation of diets that support liveweight gains (LWG) in excess of that achieved on good-quality forage diets. Three experiments were conducted with the aim of achieving LWGs in excess of 1 kg/day, measuring the eating quality of the beef and determining the long-term health of cattle fed high-molasses diets. In the first experiment, the inclusion rates of molasses were 30%, 45%, 60% and 72.5% of dietary DM. All diets were formulated to contain14% crude protein and, apart from the diet with 72.5% molasses, contained at least 12% roughage. The LWGs of Brahman steers, initial mean weight 299 kg, for the first 80 days of the feeding period were 1.3, 1.8, 1.6 and 1.1 kg/day respectively. The gains of the steers fed the 45% molasses diet were significantly (P < 0.05) higher than those fed the 30% and 72.5% diets. Over the entire measurement period of 140 days, the LWGs were 1.2, 1.4, 1.5 and 1.2 kg/day respectively. Subjective assessment of meat eating quality by untrained panellists showed that beef from all treatments groups met the standard for a good everyday eating-quality rating by the Meat Standards Australia grading system. Treatment differences were not significant. No animal health issues were apparent. A second experiment investigated the progressive substitution of molasses by sorghum grain. Mean LWGs of Brahman steers over an 84-day feeding period were 1.2, 1.4, 1.4 and 1.4 kg/day for diets of molasses to grain proportions of 60 : 0, 40 : 20, 20 : 40 and 5 : 55 respectively. There were no significant treatment differences for LWGs, feed conversion efficiencies and meat-eating quality. A third experiment determined that cattle have the capacity to excrete the high potassium (K) load associated with high-molasses diets, with urine being the major route of excretion. It was concluded that high-molasses diets could be used for intensive feeding of cattle.