EFFECTS OF EXTRUDED CORN OR GRAIN-SORGHUM ON INTAKE, DIGESTIBILITY, WEIGHT-GAIN, AND CARCASSES OF FINISHING STEERS

We conducted two trials to evaluate the effects of extruding vs dry-ro lling either corn or grain sorghum on intake, digestibility, and perfo rmance of finishing steers. In Trial 1, 92 crossbred steers (average B W 413 kg) were used in a 2 x 2 factorial design. Diets contained eithe r dry-rolled corn (RC), extruded corn (EC), dry-rolled grain sorghum ( RGS), or extruded grain sorghum (EGS). Diets were fed for 110 d and co ntained 78.6% of the respective grain, 9% alfalfa pellets, 8.2% molass es, and 4.2% protein-mineral supplement. Daily gain was highest (P < . 049) for steers fed RC, and the ADG of steers fed RGS was higher than that of steers fed extruded diets; there was no difference in ADG betw een steers fed EC and those fed EGS. Steers fed dry-rolled diets consu med more DM (P = .001) than steers fed extruded diets. Feed efficiency was not affected (P = .18) by processing method, but steers fed corn utilized the diets more efficiently (P = .006) than steers fed grain s orghum. Except for carcass weight, carcass data were not affected by g rain type (P > .20). Dressing percentage, quality grade, and longissim us muscle area were lower (P < .09) in steers that received extruded g rain than in those that received dry-rolled grain. In Trial 2, five ru minally cannulated crossbred steers (average BW 518 kg) were used in a 4 x 4 + 1 Latin square design to evaluate the ruminal and total tract digestion characteristics of the diets used in Trial I. Type of grain had no effect (P > .16) on intake, total tract digestibility, or rumi nal pH. Extruding corn or grain sorghum decreased intake (P < .001) bu t increased (P < .074) DM and starch digestibility compared with dry r olling; steers fed extruded diets had lower (P < .032) ADF and NDF dig estibilities. Ruminal in situ DM and starch disappearance were higher (P <.03) and ruminal pH was lower(P < .052) in steers fed extruded gra ins than in those fed dry-rolled grains. Data from this study indicate that extruded corn and extruded grain sorghum are highly degradable f eeds; however, decreased DM intake and lower ruminal pH levels resulte d in lower performance.