INFLUENCE OF FLAKE THICKNESS ON THE FEEDING VALUE OF STEAM-ROLLED WHEAT FOR FEEDLOT CATTLE

Seventy-two medium-framed, crossbred steers (348 kg) were used in a ra ndomized complete block design performance trial. Experimental diets c ontained (DM basis) 6% alfalfa hay, 6% sudangrass hay, 79% wheat, 2% y ellow grease, 4% cane molasses, and 3% supplement. Treatments were 1) dry-rolled wheat (DRW, density = .52 kg/L); 2) steam-rolled wheat, coa rse flake (SRW-C, density = .39 kg/L); and 3) steam-rolled wheat, thin flake (SRW-T density = .30 kg/L). Steam processing increased amyloglu cosidase reactivity of wheat starch by 238 and 287% for SRW-C and SRW- T; respectively. Cattle performance was similar (P > .10) for SRW-C an d SRW-T. Steam processing wheat increased ADG (13.5%, P < .10) and dec reased DM intake/gain (8.8%, P < .05). Diet NE was precisely as expect ed for DRW, confirming the applicability of tabular NE values. Diet NE m was 3.7% lower (P < .05) for DRW than for SRW. The NEm and NEg of SR W were 2.28 and 1.59 Mcal/kg, respectively. Twelve Holstein steers (26 6 kg) were ''T'' cannulas in the rumen and proximal duodenum were used in a completely random design experiment to evaluate treatment effect s on characteristics of ruminal and total tract digestion. Ruminal dig estibilities of OM and starch were similar (P > .10) for DRW and SRW. Postruminal and total tract digestibility of OM (P < .10) and starch ( P < .01) were increased with SRW. Dietary DE and ME values were greate r (6.1 and 6.6%, respectively; P < .10) for SRW than for DRW. The DE a nd ME values for SRW were 4.13 and 3.41 Mcal/kg, respectively. Ruminal degradation of feed N absorption increased (11%, P < .05) with SRW. T he advantages of SRW compared with DRW include 1) enhanced energy inta ke and ADG, 2) improved feed efficiency, 3) increased NE value, and 4) increased ruminal escape and postruminal absorption of feed N. There is no apparent benefit to decreasing the thickness of SRW to 1.35 mm.