Rate of starch degradation, apparent digestibility and rate and efficiency of steer gain as influenced by barley grain volume-weight and processing method

Abstract

The effects of barley grain volume-weight and processing method on rate of starch degradation, apparent digestibility, metabolizability and rate and efficiency of growth of steers were examined in a series of trials. The organic matter in an all-concentrate diet containing light barley grain (43 kg hL⁻¹) was 2% less (P = 0.03) digestible than organic matter in diets containing heavier barley grains (59, 64 and 66 kg hL⁻¹). No differences (P = 0.19) in methane production due to barley volume-weight were detected. Rates of gain (1.63–1.67 kg d⁻¹, P = 0.90) and dry matter (DM) intakes (9.8–10.2 kg d⁻¹, P = 0.52) of steers were not affected by including barley grains of differing volume-weights (43, 59 and 64 kg hL⁻¹) in the diet of 90 growing-finishing steers. Steers fed the light barley had a 6% increase (P = 0.27) in DM:gain requirements in comparison with steers fed the two heavier barley grains. Steam-rolling barley in comparison with dry-rolling had no effect on either animal growth rate (1.66 versus 1.64 kg d⁻¹, P = 0.84) or DM:gain ratio (6.15 versus 5.98, P = 0.40). Carcass characteristics were not influenced by grain type or grain processing method. Differences (P < 0.05) were detected in the rate of degradation of starch by amyloglucosidase among three barley grains. Starch in steam-rolled barley was degraded faster (P < 0.05) than starch in dry-rolled barley. Key words: Barley grain, steers, digestibility, gain, efficiency, starch degradation