Starch inclusion in beef cattle finishing diets

Abstract Text: In both the dry and wet corn milling industries, starch is removed from corn and further processed to make a number of products.  Feed byproducts from these industries contain low concentrations of starch (< 5%).  Cattle have the ability to use fiber, fat, protein, or starch for energy.  A meta-analysis of 20 cattle feeding experiments evaluated if cattle benefit from starch in the diet, or if the energy requirement can be met using other energy sources.  Within these experiments, 117 diets were fed to 708 pens of cattle.  Diets contained distillers grains plus solubles (DGS; 353 pens), wet corn gluten feed (WCGF; 5 pens), solubles (20 pens), a blend of DGS and WCGF (184 pens), or no byproduct (146 pens).  Cattle were fed as calf-feds (255 pens) or yearlings after being backgrounded with forage-based diets (453 pens).  Cattle performance was measured on each pen of cattle, thus, pen means were used in the meta-analysis.  Performance measurements included DMI, ADG, G:F, marbling score, and fat depth.  Experiment was included in the model as a random effect and type of byproduct in the diet was included as a covariate.  Data were analyzed using 5 sub-classes of corn inclusion: 0% corn (69 pens), 1-25.9% corn (28 pens), 26-50.9% corn (238 pens), 51-75.9% corn (270 pens), and ≥76% corn (103 pens).  Amount of starch, or corn, in the diet had no effect (P = 0.63) on yearling DMI, but a quadratic response (P < 0.01) was observed for calf-feds, with maximum DMI at 64% corn inclusion.  Yearling and calf-fed ADG responded quadratically to corn inclusion (P < 0.01).  Maximum ADG was at 43.8% corn inclusion for yearlings (1.74 kg/d) and 56.4% for calf-feds (1.78 kg/d).  Yearling and calf-fed G:F responded quadratically (P < 0.01).  Maximum G:F was at 49.8% corn inclusion for yearlings (0.159) and 53.4% for calf-feds (0.185).  Marbling score and fat depth were not affected by cattle age (P ≥ 0.13) and responded quadratically to corn inclusion (P < 0.01).  Maximum marbling score was at 82.1% corn inclusion while maximum fat depth was at 56.7% corn inclusion.  Maximum ADG and G:F were observed with approximately 50% corn inclusion, reflecting improved performance when byproducts replace a portion of corn.  Complete removal of corn reduced performance, although it is not clear if this is due to lack of starch or negative effects of high byproduct diets, such as fat or sulfur levels.

Keywords: byproducts, feedlot cattle, starch