A survey of starch availability of steam-flaked corn in commercial feedlots evaluating roll size and flake density1

The quality of steam-flaked corn (SFC) in feedlot diets can affect animal performance and the incidence of digestive disorders. Therefore, this study was conducted to define important and relevant measures used to determine SFC quality in commercial feedyards. Commercial feedlots (n = 17) located in Kansas, Nebraska, Texas, New Mexico, Arizona, and California were asked to participate in a survey to evaluate SFC manufacturing practices implemented, equipment used, and parameters targeted to measure flake quality. Manufacturing practice parameters evaluated included dry corn moisture, grain water addition, tempering time, steaming time, steam-cabinet temperature, mill electrical load, steam-conditioned corn moisture content, SFC moisture content, and SFC flake thickness. Equipment evaluated included roll size and steam-cabinet dimensions and capacity; flake quality parameters evaluated included hot and cooled SFC flake density, SFC volumetric flake weight, and starch availability of SFC samples. Samples of steam-conditioned corn and SFC were collected from each flaker (n = 49) within each feedlot. Flake density was measured on hot (immediately from below the rolls) and cooled flakes, and volumetric weight was measured only on cooled flakes. Steam-flaked corn samples were evaluated for starch availability using enzymatic hydrolysis. Enzymatic starch availability (ENZ) averaged 50.6 ± 8.02, with a range of 37.0 to 65.0%. Significant (P < 0.10) variables contributing to the final multiple linear regression model using ENZ as the dependent variable were SFC moisture, cooled flake density (CFD), and roll diameter [ENZ = 119.72 − (1.22 × SFC moisture) − (2.42 × CFD) + (0.47 × roll diameter); R2 = 0.5276; P < 0.10].