EVALUATION OF PERFORMANCE CARCASS CHARACTERISTICS, AND RUMINAL BUFFERING OF FEEDLOT CATTLE CONSUMING DIETS CONTAINING CORN-GRAIN MILLING BYPRODUCTS
Spowart, Paige Rebecca
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Feeds such as Sweet Bran™ (SB) and wet distillers grains with solubles (WDGS) contribute high concentrations of dietary energy and low starch while potentially providing buffering qualities that may improve rumen health and performance. Feeding combinations of SB and WDGS is common but research is limited. This study evaluated the effects of SB and WDGS in the diet alone or in combination on performance, carcass characteristics, ruminal pH, and rumination time of finishing beef cattle. The study was a randomized complete block design using pen as the experimental unit. Steers (n = 455; 373 ± 15.5 kg) were randomly allocated to 48 pens (12 blocks, 4 pens/block) and transitioned over 20 d 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 an indwelling ruminal pH bolus to quantify pH of the rumen 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, NDF concentration, and physically effective fiber (peNDF). Cattle performance (BW, DMI, ADG, G:F) was not different (P = 0.96) through the transition period across all treatments. Overall, final BW, DMI, and ADG were greater (P < 0.01) for WDGS, SB, and COMBO than CON. Although overall G:F was not different (P = 0.48), feed cost of gain was greatest (P < 0.01) for CON, intermediate for WDGS and SB and least for COMBO. Hot carcass weight was greatest (P = 0.04) for SB and WDGS, intermediate for COMBO, and least for CON. A tendency (P = 0.09) was observed for yield grade; it was greatest for WDGS, intermediate for SB and COMBO, and lowest for CON. Dressing percentage, marbling score, quality grade, 12th-rib fat, ribeye area, and percentage KPH fat did not differ (P ≥ 0.32) among treatments. Abscessed livers were not statistically different (P = 0.27), but CON had a numerically greater percentage of liver abscesses. The percentage of particles > 4.0 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 × day interaction (P < 0.01) was observed for daily rumination minutes per kg of DMI, NDF, and peNDF. A treatment × h interaction (P < 0.01) was observed such that CON cattle spent less time ruminating at 0800 and 1000 h in a 24 h period. Ruminal pH was greatest (P < 0.01) for COMBO, intermediate for SB and WDGS, and least for CON, but SB did not differ from COMBO or WDGS. 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 WDGS similarly enhance buffering capacity when steam-flaked corn is replaced in the diet.