Effect of corn particle size and soybean meal treatment on performance of finishing beef steers fed corn-silage-based diets

In the first experiment, 39 medium-frame beef steers (456 +/- 41 kg) were used in a 2 x 2 factorial arrangement of treatments to evaluate the effect of different feeding strategies to maximize energy and protein deposition on finishing performance and plasma amino acid profile of beef steers fed corn silage ad libitum for 99 d. To achieve this goal, steers were individually supplemented with either 6.6 kg DM d(-1) of cracked corn (CC) or ground corn (GC) in combination with 540 g DM d(-1) of either solvent extracted (SS) or lignosulfonate-treated soybean meal (Soypass (R); SP). Dry matter intake, average daily gain and feed to gain ratio were not affected by treatments or by their interaction (P > 0.10). When compared with SS, SP tended to increase (P = 0.07) grade fat (1.3 and 2.2 +/- 0.5 mm, respectively). The CC diets reduced the plasma concentration of branched-chained amino acids (P = 0.03) and leucine (P = 0.01), and tended to decrease that of isoleucine (P = 0.06) compared with the GC diets. No effect of diet was observed on plasma urea-N concentration. In the second experiment, four steers were used in a 4 x 4 Latin square design to evaluate digestibility and N balance of the diets used in exp. I. Reducing particle size of corn increased apparent digestibility of starch (P = 0.01) and tended to reduce apparent digestibility of NDF (P = 0.07). In conclusion, formulating diets with ground or cracked corn in combination with solvent extracted or lignosulfonate-treated soybean meal does not appear to influence steer performance or digestion parameters.