Effect of simulated air-lift and conveyor leg takeaway systems on starch availability and in vitro dry matter disappearance of steam-flaked corn grain

An experiment was conducted to determine effects of simulated air-lift (AIR) and auger/drag-chain leg (LEG) takeaway systems on starch availability (SA) and in vitro dry matter disappearance (IVDMD) of steam-flaked corn grain. At a commercial feedlot in Texas (USA) on 3 different days, corn grain was steam flaked to a bulk density of 360 g/l. At three random times per day, grain was sampled beneath the rolls, with a portion allocated to initial measurement of flake color with the flake camera index system (FCIS). The remaining grain was allocated to the AIR and LEG treatments. For AIR, flaked grain was placed in a Styrofoam cooler, cooled to 37.8 °C, covered and stored for 4 h. For LEG, flaked grain was placed in a Styrofoam cooler, covered immediately and stored for 4 h. After the 4 h storage period, three random samples of corn grain from each treatment were analyzed for SA, flake color and IVDMD. The AIR samples had higher (P<0.001) SA than LEG samples (0.522 versus 0.313, respectively). Similarly, AIR samples had higher (P<0.001) IVDMD at 4 and 24 h versus LEG samples. Correspondingly, half time of disappearance (t1/2) was higher (P=0.06), for AIR versus LEG samples. The FCIS measurements did not differ between initial and 4 h AIR and LEG samples. Results indicate that rate of cooling of freshly processed steam-flaked corn grain as influenced by simulated takeaway system may affect starch retrogradation. Whether the magnitude of these differences under commercial feedlot conditions elicits a difference in animal performance remains to be determined.