No abstract

Roughage is fed in finishing diets to promote ruminal health and decrease digestive upset, but the inclusion rate is limited because of the cost per unit of energy and feed management issues. Rumination behavior of cattle may be a means to standardize roughage in beef cattle finishing diets, and increasing the particle size of roughage could modulate the ruminal environment and aid in maintaining ruminal pH. Therefore, this experiment was conducted to determine the effects of corn stalk (CS) inclusion rate and particle size in finishing diets on digestibility, rumination, and ruminal fermentation characteristics of beef steers. Four ruminally cannulated steers were used in a 4 × 4 Latin square experiment. Treatments were arranged as a 2 × 2 factorial with treatments consisting of 5% inclusion of a short-grind roughage (5SG), 10% inclusion of a short-grind roughage (10SG), 5% inclusion of a long-grind roughage (5LG), and 10% inclusion of a long-grind roughage (10LG). Differences in particle size were obtained by grinding corn stalks once (LG) or twice (SG) using a commercial tub grinder equipped with a 7.6-cm screen and quantified using the Penn State Particle Separator (PSPS) to estimate physically effective NDF (peNDF). Each period included 14 d for adaptation and 4 d for diet, fecal, and ruminal fluid collections. Animals were outfitted with rumination monitoring collars to continuously measure rumination activity. The 10LG treatment had a greater ( < 0.01) percentage of large particles (retained on the top 3 sieves of the PSPS) compared to the other treatments. This resulted in a greater ( < 0.01) percentage of estimated peNDF for the 10LG diet compared to the others. Feeding diets containing 5% roughage tended to increase ( ≤ 0.09) DM, NDF, and starch total tract digestibility compared to diets containing 10% roughage. Cattle consuming LG treatments had greater ( < 0.01) rumination time and greater ( < 0.01) ruminal pH than cattle consuming diets containing SG roughage. Cattle receiving the 5% inclusion rate of roughage tended to have greater ( = 0.09) time (h/d) under a ruminal pH of 5.6 and a larger ( = 0.03) area under the threshold compared to cattle receiving the 10% roughage treatments. Overall, feeding a lower inclusion of roughage with a larger particle size may stimulate rumination and aid in ruminal buffering similar to that of a higher inclusion of roughage with a smaller particle size, without negatively impacting digestibility and fermentation.

Two experiments were conducted to evaluate the effects of feeding condensed distiller's solubles (DS) and crude glycerin alone or in combination on performance of finishing beef cattle and in vitro fermentation. In both experiments, dietary treatments consisted of a steam-flaked corn-based diet with 0% DS or crude glycerin (CON), 10% DS (CDS), 10% crude glycerin (GLY), or a combination of 5% DS and 5% crude glycerin (C+G) included on a DM basis. All treatment diets contained 15% (DM basis) wet distiller's grains plus solubles. In Exp. 1, crossbred steers ( = 256; 322 ± 15 kg initial BW) were used in a randomized complete block finishing trial. Growth performance and gain efficiency were not different ( > 0.10) across all treatments. Treatment had no effect ( > 0.10) on carcass weight, marbling score, yield grade, LM area, or percent grading USDA choice. In Exp. 2, ruminal fluid was collected from 2 ruminally cannulated steers to evaluate in vitro fermentation characteristics. No differences ( = 0.43) were observed for DM disappearance across all treatments. The GLY and C+G treatments had decreased ( = 0.02 and = 0.05, respectively) NDF disappearance (NDFD), whereas the CDS treatment tended to have decreased ( = 0.06) NDFD compared with CON. Concentrations of NH decreased ( < 0.04) with GLY and C+G treatments compared with CON. Total gas production decreased ( < 0.01) for the C+G treatment compared with other treatments. The CDS treatment had increased ( < 0.02) total VFA compared with the CON or C+G treatments. Treatments had no effect ( > 0.17) on concentrations of acetate, propionate, and butyrate, but valerate concentrations were the greatest ( < 0.04) for the CON treatment. Concentrations of isobutyrate increased ( < 0.05) for the CON and C+G treatments compared with the GLY treatment and tended to increase ( < 0.10) compared with the CDS treatment. Including DS or glycerin in the substrates decreased ( < 0.08) isovalerate compared with CON. Feeding additional byproducts such as DS and crude glycerin alone or in combination in a finishing diet did not alter live animal performance or carcass characteristics; however, feeding a combination of the 2 byproducts may alter in vitro fermentation.

No abstract