The value of soybean hulls as a replacement for corn in beef cattle diets formulated with or without added fat

One hundred twenty crossbred yearling steers (average weight = 445 +/- 32 kg) were used in an 84-d randomized complete block design experiment to determine the value of soybean hulls (SH) as a replacement for corn in concentrate diets formulated with or without added fat (lard). The steers were blocked by weight and allotted to one of eight treatments in a 4 X 2 factorial arrangement of treatments. The main factors were amount of SH (0, 20, 40, or 60% of diet DM) and amount of added fat (0 or 5% of diet DM). The basal diet without added fat or SH contained cracked corn (80%), a urea-based protein supplement (15%), and ground corn cobs (5%). Replacing corn with SH linearly (P = .03) decreased ADG, increased DMI (linear, P = .003; quadratic, P = .06), and linearly (P < .001) decreased gain efficiency. Fat addition tended (P = .08) to improve efficiency; ADG and DMI were unaffected (P > .05) by fat addition. Similar diets were fed to 16 wethers (average weight = 47 +/- 2.3 kg) in a randomized complete block design experiment to determine digestibility of NDF and dietary concentration of DE. Replacing corn with SH linearly increased DMI (P = .001) and NDF (P < .001) and linearly decreased (P < .001) the digestibility of DM. The digestibility of NDF tended to increase with increased SH. The digestibility of energy linearly (P = .0001) decreased with increased SH. The amount of fat had no effect (P > .05) on DMI or intake of NDF or digestibilities of these nutrients. The addition of fat tended (P = .07) to improve the intake of DE. For the conditions of this study, addition of fat to diets had similar effects on performance regardless of the dietary amount of SH. The feed value of SH was estimated as 74 to 80% of that of corn. The use of SH in concentrate diets should be dictated by the cost of SH relative to cereal grains within the context of reduced gain and efficiency, particularly when SH are fed at high concentrations of diet DM.