Biofuel co-products as livestock feed - Opportunities and challenges

77Chapter 5Utilization of feed co-products from wet ordry milling for beef cattleG.E. Erickson, T.J. Klopfenstein and A.K. WatsonDepartment of Animal Science, University of Nebraska-Lincoln, C220 Animal Science Lincoln, Nebraska 68583-0908, United States of AmericaE-mail for correspondence: gerickson4@unl.eduABSTRACTRecent expansion of the ethanol industry has led to an increase in production of co-products that are used extensivelyin the cattle industry. A variety of different co-products are being produced, all with slightly different nutrientcompositions. Maize [corn] gluten feed (CGF) is the main co-product of the wet milling industry, while distillersgrains with solubles (DGS) is the main feed produced by dry milling plants. These co-products have little to nostarch remaining, which reduces acidosis challenges in feedlot cattle and reduces negative associative effects ofstarch digestion on fibre digestion for cattle on high forage diets. The extent to which an ethanol plant dries theseco-products affects their nutritional value. For feedlot cattle, wet DGS (WDGS) have a feeding value 30–40 percentgreater than maize when included at 10–40 percent of diet DM. Modified and dried DGS have feeding values15–30 percent and 13 percent greater than maize, respectively. Because feeding DGS results in improved cattleperformance, cattle can be fed for fewer days resulting in decreased costs. Feeding high levels of DGS increasesthe sulphur content of diets and may decrease performance or result in polio encephalo malacia (PEM), particularlyif sulphur levels exceed 0.47 percent of diet DM. Increasing roughage levels in the diet appears to be an effectiveway of minimizing sulphur impacts and maintaining cattle performance. In addition, lower quality roughages couldbe fed in feedlot diets containing WDGS without diminishing performance. Intense maize processing increases thevalue of diets containing CGF. However, greater performance responses have been seen with less intensely processedmaize in diets containing DGS. There appear to be many complex interactions that cause these differencesin performance, and warrant further study.The environmental impacts of these co-products are quite important. The ideal scenario for reducing greenhousegas (GHG) emissions of ethanol involves feeding WDGS to feedlot cattle within 100 km of the ethanolplant. In this scenario, GHG emissions can be reduced by 56–62 percent compared with gasoline due to improvedcattle performance and decreased energy costs at the ethanol plant when DGS is not dried. Feeding high levelsof co-products increases nitrogen (N) and phosphorous (P) in the diet, which increases the N and P content of themanure. Capturing these nutrients in the manure and applying to crop land as fertilizer increases the value of themanure above the costs to apply it. These co-product feeds are an excellent source of energy, protein and P forcattle on high forage diets, and quadratic increases in average daily gain (ADG) and final bodyweight (BW) havebeen observed with increasing levels of DGS supplementation.INTRODUCTIONTwo primary types of grain milling processes currently exist,resulting in quite different feed products. These processingplants produce and market a variety of feed products, butin general, the dry milling process produces distillers grainswith solubles (DGS), and the wet milling process producesmaize gluten feed (CGF). These feeds can be marketed aswet feeds, or they can be dried and marketed as either drymaize gluten feed (DCGF) or dried distillers grains (DDG)with or without solubles. The majority of ethanol plantexpansions are dry milling plants that produce DGS; however,an increase in supply of wet maize gluten feed (WCGF) isalso expected. Therefore, these feeds may be very attractivefor beef producers to use as feed sources. This report willfocus on the production, composition, feeding values andenvironmental issues of using these co-products in bothgrowing and finishing beef cattle diets. Management strategieswill be discussed as well, including type of grain, grainprocessing, roughage levels and the effects of fat, protein,phosphorus (P) and sulphur (S) with these products.Wet millingWet milling is a process that requires the use of high quality(U.S. No. 2 or better) maize, and fractionates the maize