Effects of increasing levels of soybean hulls in finishing diets of feedlot cattle fed free-choice hay on performance, roughage intake, and carcass characteristics

Objectives: Our objective was to evaluate the effects of incremental inclusion rates of dietary soybean hulls (SH) on finishing performance, roughage intake (RI), and carcass characteristics in feedlot cattle fed free-choice hay. Materials and Methods: Angus × SimAngus-crossbred heifers (n = 60) and steers (n = 54) were stratified by sex and BW and assigned into 12 pens. Treatment 1 contained 5% soybean hulls, 70% ground corn (GC), 15% distiller grains, and 10% mineral supplement. Treatments 2 and 3 included an additional 5% and 10% SH in place of GC, respectively. Data were analyzed as a randomized complete block (BW) design using 2 different multiple linear regression analyses considering (1) the effects of total NDF intake (TNDFI), roughage NDF intake (RNDFI), and RI variability on growth and carcass characteristics and (2) the effects of concentrate NDF intake (CNDFI) and RI variability on RI. Results and Discussion: There were treatment × sex interactions (P ≤ 0.03) for DMI, final BW and RI. In heifers, substituting 15% GC with SH increased DMI at the expense of RI. Substituting GC with SH did not affect DMI of steers, but feeding increasing SH decreased final BW. Average daily gain and DMI were negatively associated (P ≤ 0.05) with TNDFI and RNDFI. The RI was negatively (P ≤ 0.05) associated with CNDFI. The LM area of steer carcasses was negatively associated (P < 0.05) with TNDFI and RNDFI. Implications and Applications: Despite differential responses to dietary treatments between steers and heifers, cost effectiveness of replacing a small portion of corn with SH will depend on the difference of feed costs.