We evaluated the accuracy of acid insoluble ash (AIA) as a digestibility marker in feedlot cattle diets containing corn-milling byproducts and examined the effect of fecal sampling frequency on digestibility estimates. Steers (n = 6) were used in a crossover split-plot design where 3 steers per period were assigned to 1 of 2 diets [receiving (REC) containing 19% roughage and 38% Sweet Bran™ or finishing (FIN) containing 8% roughage and 20% Sweet Bran] typical of those used in the beef feedlot industry. Steers were limit fed at 2.0% of initial body weight. After a 21-d adaptation period, steers were housed in metabolism crates for 7 d of total collection (TC) of feed and feces and simultaneous collection of fresh manure grab samples twice daily to calculate nutrient digestibility from AIA. Grab samples were then averaged to represent 7 (7dAIA), 5 (5dAIA), 3 (3dAIA) and 1 (1dAIA) days of the collection period. No interactions (P ≥ 0.13) were observed for DM, OM or NDF digestibility between diet and method of estimating digestibility. Digestibility of DM and OM were greater (P < 0.01) for FIN than for REC, and NDF digestibility was less (P < 0.01) for FIN than REC. Both DM and OM digestibility were greater (P < 0.01) for AIA estimates than for TC; however, estimates with 7dAIA were less than 3dAIA and 1dAIA, but not different from 5dAIA. Similarly, NDF digestibility was greater (P < 0.01) for all AIA estimates than for TC, but 7dAIA and 5dAIA were less than 1dAIA and not different from 3dAIA. A treatment × method interaction (P = 0.02) occurred for ADF digestibility. These data suggest that AIA over-estimated digestibility of beef feedlot diets containing corn-milling byproducts, but accuracy improved with greater grab sampling frequency.

This study evaluated the effects of Sweet Bran (SB) and wet distillers grains with solubles (WDGS) in the diet alone or in combination on physically effective NDF (peNDF), ruminal pH, and rumination behavior of finishing beef cattle. For this study, 455 steers (373 ± 15.5 kg) were allocated to 48 pens in a randomized complete block design. Treatments (n = 12 pens per treatment) were 1 of 4 steam-flaked corn-based diets containing no corn-milling products (CON), 20% WDGS (WDGS20), 20% SB (SB20), or 20% SB and 10% WDGS (COMBO). Within each pen, 2 steers were randomly selected to receive an indwelling ruminal pH bolus to quantify ruminal pH and a 3-axis accelerometer tag to measure rumination for the first 92 d of the study. Diet samples were collected weekly to determine particle size, neutral detergent fiber (NDF) concentration, and peNDF. Physically effective NDF was calculated using both the proportion of particles > 4.0 mm (peNDF4.0) and the proportion of particles > 8.0 mm (peNDF8.0). The percentage of particles > 4.0 mm was greatest (P < 0.01) for CON, intermediate for SB20, and least for WDGS20 and COMBO. Both NDF (P < 0.01) and peNDF4.0 (P < 0.01) were greatest for COMBO, intermediate for WDGS20 and SB20, and least for CON. The percentage of particles > 8.0 was greatest (P < 0.01) for CON, intermediate for WDGS20 and SB20, and least for COMBO, but peNDF8.0 did not differ (P = 0.40). A diet × day interaction (P < 0.01) was observed for daily rumination minutes per kg of DMI, NDF, peNDF8.0, and peNDF4.0. A diet × hour interaction (P < 0.01) was observed where CON cattle spent less time ruminating at 0800 and 1000 h in a 24 h period. Daily ruminal pH was greatest (P < 0.01) for COMBO, intermediate for SB20 and WDGS20, and least for CON. A diet × hour interaction (P < 0.01) was also observed for circadian ruminal pH, where pH was least for CON from 0800 to 1800 h. Relationships between peNDF, rumination behavior, and ruminal pH observed in this study suggest that SB and WDGS similarly enhance rumen buffering capacity when steam-flaked corn is replaced in the diet.

This study evaluated the effects of Sweet Bran™ (SB) and/or wet distillers grains with solubles (WDGS) in the diet alone or in combination on performance, carcass characteristics, ruminal pH, and rumination of finishing beef cattle. Steers (n = 455) were randomly allocated to 48 pens and assigned to 1 of 4 steam-flaked corn-based dietary treatments containing: no byproducts (CON), 20% WDGS (WDGS), 20% SB (SB), or 20% SB and 10% WDGS (COMBO). Within each pen, 2 steers were randomly selected to receive a ruminal pH bolus and ear tag to quantify pH and rumination. Diet samples were collected weekly to determine particle size and physically effective fiber. Final BW, DMI, and ADG were greater (P < 0.01) for WDGS, SB, and COMBO than CON. Hot carcass weight was greatest (P = 0.04) for WDGS and SB, intermediate for COMBO, and least for CON. Yield grade tended (P = 0.09) to be greater for WDGS, SB, and COMBO than CON. A numerical increase in abscessed livers was observed for CON. The percentage of particles > 4 mm was greatest (P < 0.01) for CON, intermediate for SB, and least for WDGS and COMBO. However, NDF (P < 0.01) and peNDF (P < 0.01) were greatest for COMBO, intermediate for WDGS and SB, and least for CON. A treatment × time interaction was observed as CON cattle spent less time ruminating at 0800 and 1000 h (P < 0.01) in a 24h period. Ruminal pH was least (P < 0.01) for CON from 0800 to 1800 h. Addition of WDGS and/or SB improved performance and reduced feed cost of gain when incorporated into steam-flaked corn-based finishing diets. Relationships between peNDF, rumination behavior, and ruminal pH suggest that SB and/or WDGS enhance buffering capacity when steam-flaked corn is replaced in the diet.