Influence of Tempering and Steaming Requirements of Flaked Corn for Feedlot Cattle Diets

Five trials were conducted to evaluate the influence of tempering and time, delivery rate and pressure of steam on the feeding value of Steam-Flaked Corn (SFC) for feedlot cattle. Trial 1, 4 Holstein steer with cannulas in the rumen and proximal duodenum were used in a 4x4 Latin square design. Treatments were: Dry Rolled Corn, no steam (DRC); Tempered Rolled Corn, no steam (TRC), tempered flaked corn, 5 min steaming time (T-5 min-SFC) and flaked corn, 25 min steaming time (25 min-SFC). There were no treatments effects (p > 0.10) on ruminal digestion of OM, DIP and ruminal microbial efficiency. There was a tendency (p = 0.19) for ruminal NDF digestion to be lower For 25 min-SFC than for T-5 min-SFC. Ruminal starch digestion was greater (14.1%, p < 0.05) for steam-flaked corn treatments than for rolled corn treatments. Ruminal N efficiency tended to be greater (p = 0.13) for steam flaked corn treatments then for rolled corn treatments. Post ruminal and total tract digestion of OM, starch and N were greater (p < 0.05) for steam-flaked corn treatments than for rolled corn treatments (36.8 and 19.3%, respectively). Ruminal pH was lower (4.8%, p < 0.05) for steam-flaked corn treatments than for rolled corn treatments. Ruminal acetate: propionate molar ratios and estimated methane production were also lower for steam-flaked corn treatments than for rolled corn treatments. In trial 2, eighty crossbred heifers (248 kg BW) were used in a 105 day randomized complete block design experiment to evaluate treatment effects: No tempering and 117 kPa of steam pressure (NT117); no tempering and 379 kPa of steam (NT379); Tempering and 117 kPa of steam (T117) and Tempering and 379 kPa of steam pressure (T379). There were no treatment effects (p > 0.10) on ADG, DMI, gain efficiency, or dietary NE. In trial 3, 4 Holstein steer with ruminal and duodenal cannulas were used in a 4x4 Latin square to evaluate characteristics of digestion of dietary treatment fed in trial 2. Tempering did not affect (p > 0. 10) ruminal digestion of OM, starch, or N. However, it increased (p < 0.05) post ruminal and total tract digestion of OM (3.4 and 1.4%, respectively) and N (0.6 and 3%, respectively). Increasing steam pressure from 117-379 kPa increased (p < 0.05) post ruminal (3.8%) and total tract starch digestion (0.8%). Ruminal and total tract starch digestion averaged 82 and 98%, respectively. In trial 4, 96 crossbred steer calves (347 kg BW) were used in a 56 day trial to evaluate treatment effects on performance and dietary NE value. Treatments were: no tempering and 419 kPa along a 6.35 diam steam line, measured 90 cm proximal to steam chest splitter valves. (NT419); no tempering and 335 kPa of steam (NT335); tempering and 419 kPa of steam (T419) and tempering and 335 kPa of steam pressure (T335). There were no treatment effects (p > 0.20) on ADG (1.24 kg day(-1)), DM conversion (5.60 kg DM kg(-1) ADG) and dietary NE for maintenance and gain (2.24 and 1.55 Mcal kg(-1), respectively). In trial 5, 4 Holstein steer with ruminal and duodenal cannulas were used in a 4x4 Latin square design to evaluate characteristics of digestion of dietary treatments fed in trial 4. Percentage of corn starch that was reactive to amylglucosidase (a measure of starch solubility) was similar across SFC treatments, averaging 22%. Ruminal digestion of OM averaged 65.0% and was not affected (p > 0.20) by treatments. Tempering increased (4.6%, p < 0.05) ruminal starch digestion. However, ruminal starch digestion was not influenced by steam reduction (80. 7 vs80.4%, p > 0.20). Total tract digestion of OM and starch also were not affected (p > 0.20) by treatments, averaging 68.3 and 97.7%, respectively. We conclude that optimal feeding value can be achieved from flaked corn using considerably less steam than is customary in the industry. However, under conditions of lower steam delivery rates, more than 50 min tempering time may be required to soften the corn sufficiently to maintain high roller output rates. Provided that the lower quarter of the steam chest is maintained at temperature greater than 100 degrees C, reducing steam application by as much as 20% will not detrimentally affect the feeding value of SFC.