Effects on roughage inclusion and particle size on digestion and ruminal fermentation characteristics of beef steers

Authors: WEISS, CALEB - Texas Agrilife Research; GENTRY, WES - Texas Agrilife Research; MEREDITH, C - Texas Agrilife Research; Meyer, Beverly; COLE, NOEL - Retired ARS Employee; TEDESCHI, LUIS - Texas A&M University; MCCOLLUM, F - Texas Agrilife Extension; JENNINGS, JENNY - Texas Agrilife Research

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2017
Publication Date: 4/13/2017
Citation: Weiss, C.P., Gentry, W.W., Meredith, C.M., Meyer, B.E., Cole, N.A., Tedeschi, L.O., Mccollum, F.T., Jennings, J.S. 2017. Effects on roughage inclusion and particle size on digestion and ruminal fermentation characteristics of beef steers. Journal of Animal Science. 95:1701-1714. doi:10.2527/jas2016.1330.

Interpretive Summary: Roughage is fed to cattle to promote ruminal health and decrease digestive upset. However, inclusion of roughage in finishing diets is limited because of its high cost per unit of available energy. By mesuring rumination behavior of feed to cattle it might be possible to determine optimal quantities and forms of roughage to use in finishing diets. Therefore, scientists from ARS (Bushland, Texas) and Texas A&M AgriLife Research and Extension Service conducted an experiment to determine the effects of the quantity (5 or 10% of diet dry matter) and particle size of corn stalks in finishing diets on diet digestibility, rumination behaviour, and ruminal fermentation characteristics of beef steers. Overall, feeding cattle a 5% long-grind roughage stimulated rumination and ruminal buffering similar to that of a 10% inclusion of roughage with a shorter particle size, without the negatively impacting digestibility and ruminal fermentation. Keywords: beef cattle, particle size, roughage, rumination

Technical Abstract: Roughage is fed to cattle to promote ruminal health and decrease digestive upset, but inclusion in finishing diets is limited due to the cost per unit of energy. Rumination behavior may be a means to standardize roughage in beef cattle finishing diets, and increasing particle size of roughage could modulate the rumen environment and aide in maintaining rumen pH. Therefore, an experiment was conducted to determine the effects of corn stalks (CS) 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 days for adaptation and 4 days 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 (P < 0.01) percentage of large particles (retained on the top three sieves of the PSPS) compared to the other treatments. This resulted in a greater (P < 0.01) percentage of estimated peNDF for the 10LG diet compared to the others. Feeding diets containing 5% roughage tended to increase (P = 0.09) DM, NDF, and starch total tract digestibility compared to diets containing 10% roughage. Cattle consuming LG treatments had greater (P < 0.01) rumination time, which increased (P < 0.01) ruminal pH compared to diets containing SG roughage. Diets containing 5% roughage had greater (P < 0.01) total VFA and increased (P < 0.01) proportions of propionate compared to diets containing 10% roughage. 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 larger particle size, without the negatively impacting on digestibility and fermentation. Keywords: beef cattle, particle size, roughage, rumination