The Use of a Rumination Monitoring Device for Finishing Beef Steers Receiving Different Particle Size and Inclusion Rate of Dietary Roughage.

New technologies have immerged to aide in establishing the appropriate recommendations for roughage inclusion in finishing diets. Two experiments were completed using a collar (HR Tag; SCR Dairy, Netanya, Israel) which measured rumination minutes continuously via a sensory microphone. Different grind sizes of corn stalks were fed at 5 or 10% inclusion (DM basis; DMB) to determine their effects on feedlot performance, rumination behavior, and ruminal fermentation characteristics of beef steers. Differences in particle size were obtained by grinding corn stalks once (LG) or twice (SG) using a tub grinder equipped with a 7.62 cm screen and quantified using the Penn State Particle Separator to estimate physically effective NDF (peNDF). Experiment 1 was a feeding study using steam-flaked corn-based finishing diets fed with 10% SG (10SG), 5% SG (5SG), and 5% LG (5LG; DMB). Steers were fed once daily using Calan head gates for an average of 155 d. Experiment 2 was a metabolism study using diets from Exp.1 with an additional treatment diet containing 10% LG (10LG; DMB). Four ruminally cannulated steers were used in a 4 × 4 Latin square experiment. Treatments were arranged as a 2 × 2 factorial. Each period included 14 d for adaptation and 4 d for diet, fecal, ruminal fluid collections, and rumination activity. Overall, long grind corn stalks contained more (P < 0.01) peNDF than SG, and the 10LG had the greatest (P < 0.01) percentage of estimated peNDF than the other treatments. In Exp. 1, carcass-adjusted ADG, G:F, and dressing percent were greatest (P ≤ 0.03) for steers consuming 5LG and 5SG than 10SG. A significant interaction (P < 0.01) occurred for rumination min x day. Rumination (min/day) were greatest (P = 0.01) for steers consuming 10SG, followed by 5LG, and lowest for 5SG. In Exp. 2, cattle consuming LG had greater (P < 0.01) rumination time, and greater (P < 0.01) ruminal pH than cattle consuming diets containing SG. Cattle receiving the 5% inclusion rate of roughage tended to have greater (P = 0.09) time (hr/d) under a ruminal pH of 5.6 and a larger (P = 0.03) area under the threshold compared to 10% roughage treatments. Feeding a lower inclusion of roughage with a larger particle size may aid in ruminal buffering similar to that of a higher inclusion of roughage with a smaller particle size, without negatively impacting fermentation and feedlot performance.