Effects of replacing barley grain with graded levels of wheat bran on rumen fermentation, voluntary intake and nutrient digestion in beef cattle

Friedt, A. D., McAllister, T. A., He, M. L., Penner, G. B. and McKinnon, J. J. 2014. Effects of replacing barley grain with graded levels of wheat bran on rumen fermentation, voluntary intake and nutrient digestion in beef cattle. Can. J. Anim. Sci. 94: 129-137. Abrasion-milled wheat bran (AMWB) is a relatively new by-product from wheat-based ethanol production. Few published studies are available on the nutritional value of this by-product feed for growing cattle. The objective of this trial was to evaluate the effects of replacing rolled barley with AMWB on apparent nutrient digestibility, voluntary intake and rumen fermentation parameters of beef heifers fed a backgrounding diet formulated to 1.50 and 0.91 Mcal kg⁻¹ dry matter (DM) of NEₘ and NEg, respectively. Five spayed and rumen-cannulated Angus heifers (584±40 kg) were used in a 5×5 Latin square design. The control diet consisted of 36% barley silage, 24% grass hay, 8% supplement and 32% rolled barley grain (DM basis). Dietary treatments replaced barley grain with AMWB at 8, 16, 24 and 32% of the diet DM. Voluntary DM (P=0.30) and organic matter (OM) (P=0.19) intake were not affected by AMWB inclusion level. Mean rumen pH (P=0.68) as well as duration (min) (P=0.68) and area under the pH curve 5.8 (P=0.27) were not affected by AMWB. Other than acetate, which linearly increased (P=0.03) with increasing AMWB, effects on rumen volatile fatty acids or NH3-N levels were minimal. There was a linear decrease (P<0.01) in DM, OM and gross energy digestibility with increasing AMWB, while acid (P=0.01) and neutral (P=0.03) detergent fibre digestibility decreased in a quadratic manner. A similar quadratic trend (P=0.06) for decreased digestible energy content was also noted with increasing levels of AMWB. Crude protein digestibility was not affected (P=0.94) by treatment. These results indicate AMWB will not support similar gains to barley grain in growing diets due to reduced total tract nutrient utilization and lower digestible energy content.