Effects of forage type and concentrated separator by-product (CSB) on intake and digestion in beef steers. (Ruminant Nutrition and Forages)

Four ruminally and duodenally cannulated beef steers (444 40 kg) were used in a 4 x 4 Latin square to evaluate effects of forage type and CSB addition on intake and digestion. Treatments were arranged in a 2 x 2 factorial. Factors were forage types (alfalfa and cornstover) and CSB additions. Concentrated separator byproduct was mixed with forage and offered at 0 or 10% of the diet DM. Experimental periods were 21 d and steers were allowed 12 d adaptation before collections began. Main effects of alfalfa and CSB will be discussed unless there were forage x CSB interactions (P < 0.10). Intakes (g/kg BW) of DM (21.4 vs 8.1) and OM (18.9 vs 7.3) were higher (P < 0.01) for steers fed alfalfa compared with those fed cornstover. Steers fed CSB consumed more (P < 0.01) DM than controls (16.4 vs. 13.2 g/kg BW). In addition, OM intake tended (P = 0.15) to be influenced by CSB addition. As expected, total tract digestions of DM, OM, and ADF were greater (P < 0.10) in steers fed alfalfa compared with cornstover (63.2 vs 54.8% for OM digestion). No effects (P > 0.10) of CSB on digestion coefficients were noted. In situ rate of NDF digestion was higher (P = 0.08) in alfalfa compared with cornstover (11.3 vs 3.8%/h) and lower in control vs CSB (6.7 vs 8.4 %/h). Interactive means for total tract CP digestion within cornstover were -26.4%, for control, and 29.0%, for 10% CSB. Interactive means differed (P < 0.10) among treatment, for in situ rate of CP disappearance, and were 9.8, 10.8, 0.8, and 7.6 0.4%/h for alfalfa, alfalfa with CSB, cornstover, and cornstover with CSB, respectively. Within alfalfa and cornstover treatment, CSB fed steers had higher in situ CP Fraction A (49.1 and 71.7 vs 36.6 and 46.5%; P < 0.10) and lower Fraction B (44.5 and 17.1 vs 51.9 and 40.9%; P < 0.10). Data suggest that feeding CSB will increase intake, and rates of digestion. Effects of CSB are more pronounced in mature forage based diets. Key Words: Forage, Intake, Concentrated Separator By-Product