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Three studies were conducted to evaluate the impact of different fiber sources and their impacts upon growth performance, carcass characteristics, and rumination characteristics of feedlot steers. The first study evaluated the effect of roughage source on rumination time and growth performance response in finishing beef steers. We hypothesized that roughage source would not affect rumination time and growth performance because dietary neutral detergent fiber (NDF) was similar across treatment diets. Steers consumed a steam-flaked corn-based diet containing corn stalks (CS), cotton burrs (CB), or wheat silage (WS) as the roughage source included at 7% dietary dry matter basis (DMB). Diets were formulated to contain similar total dietary NDF concentrations across treatments. Each steer was fitted with a sensory collar to record daily rumination. Weekly ingredient and diet samples were sieved to estimate physically effective NDF (epeNDF) using the Penn State Particle Separator. Actual physically effective NDF (apeNDF) was calculated based on rumination time. Neither initial nor final body weight (FBW) differed among treatments (P > 0.52); however, gain to feed (G:F) tended to differ (P = 0.06) among treatments, with CS having the greatest G:F compared to CB and WS. Dietary NDF and epeNDF did not differ (P ≥ 0.35) among diets; however, CB had the least apeNDF (P < 0.01), which was an outcome of less rumination time (P < 0.01). The CB daily rumination was 30% less than CS and WS. The peNDF value calculated from the Penn State Particle Separator (PSPS) overestimates the rumination potential of CB, CS and WS in feedlot finishing diets containing low (7%; DMB) roughages. The second study was conducted in tandem with the first study and utilized the same diets. We hypothesized that roughage source would not impact rumination time and ruminal pH if different roughage sources provided similar dietary NDF. This experimental objective was to evaluate rumination time and ruminal pH of beef steers consuming finishing diets with one of three roughage sources (CS-R, CB-R, or WS-R). Ruminal pH was measured using a handheld pH probe inserted through the ruminal cannula of each steer on d 21 of each period at 0, 3, 6, 12, and 24 h post-feeding. Dry matter intake dietary NDF, or epeNDF did not differ (P > 0.36) among dietary treatments. However, apeNDF and rumination time differed (P < 0.01) amongst treatments along with rumination time; CB had the lowest apeNDF, consistent with lower rumination time. However, ruminal pH did not differ among dietary treatments (P = 0.34). These results indicate that roughage source impacted rumination time despite feeding steers a steam-flaked corn-based finishing diet with similar roughage inclusions and dietary NDF levels, therefore, indicating a difference in physical structure of roughage sources. The final study evaluated the effects of dried distiller’s grains with solubles (DDGS) had on rumination and nutrient digestibility of steers fed a steam-flaked cornbased finishing ration. We hypothesized that DDGS concentration would not affect total daily rumination of finishing steers and that replacing SFC with DDGS would increase ruminal pH. Our objective was to evaluate rumination behavior and ruminal characteristics of beef steers fed steam flaked corn (SFC) based finishing diets with 15, 20, or 25% DDGS. To achieve isonitrogenous and isocaloric diets, SFC, soybean meal and corn oil were replaced with DDGS. Total daily rumination and rumination per kg of nutrient intake along with epeNDF, apeNDF, and ruminal pH did not differ across dietary inclusion of DDGS (P ≥ 0.14). Total ruminal VFA concentration (mM) tended to be greater (P = 0.07) for steers consuming 15 or 20% DDGS than steers consuming 25% DDGS. Fecal NDF output tended to differ (P = 0.07) among diets; as dietary DDGS inclusion increased, fecal NDF increased. Apparent total tract organic matter digestibility (OMD) tended to differ (P < 0.07) across diets; OMD decreased in a linear (P = 0.03) trend as DDGS inclusion increased. This data suggests that DDGS may increase ruminal pH through means other than increasing peNDF, such as starch dilution.



Agriculture, Animal Culture and Nutrition


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