Biofuel co-products as livestock feed - Opportunities and challenges

115Chapter 7Feeding biofuel co-products to dairy cattleKenneth F. Kalscheur, Alvaro D. Garcia, David J. Schingoethe, Fernando Diaz Royón and Arnold R. HippenDairy Science Department, South Dakota State University, Brookings, SD 57007, United States of AmericaEmail for correspondence: kenneth.kalscheur@sdstate.eduABSTRACTThe expansion of ethanol and biodiesel production as bio-renewable fuel sources has resulted in increased availabilityof numerous co-products as livestock feeds. The growth of the bio-ethanol industry in the United States overthe past decade has been rapid and has resulted in large quantities of distillers grain and other ethanol co-productsbecoming available for dairy cattle diets. While many types of grains can be used for ethanol production, maizegrain is the grain most commonly used in the United States. Distillers grain is often added to dairy cow diets toprovide a source of rumen-undegraded protein, energy and minerals. Distillers grain can be provided dried, wet,or in a modified wet form. In addition to distillers grain, condensed distillers solubles is a product of the ethanolindustry. Pre-fermentation fractionation and post-fermentation processes produce other co-products, such ashigh-protein distillers grain, maize germ, maize bran and reduced-fat distillers grain, all which can be utilized indairy cattle diets. From the biodiesel industry, glycerol has been investigated to determine its use in dairy cattlediets. Storage of wet co-products on the farm is challenging because wet feedstuffs will spoil quickly unless theyare stored anaerobically. Ensiling co-products alone or in combination with complementary feedstuffs have beensuccessful. In the near future it is likely that new biofuel products will become available in the market as a result ofseparation of the different nutrient fractions. Ruminant nutrition research will need to parallel these new productdevelopments to ensure maximum economic return to livestock producers.INTRODUCTIONIn 1797, and just before retiring from office, GeorgeWashington had a farm manager from Scotland whostarted a distillation plant (DISCUS, 2007). The byproductof this distillery, called “slop”, was already considered avaluable food source for livestock, allowing the president tofeed cattle and pigs with it. The advantages of using distillersgrain with solubles (DGS) as a feedstuff for dairy cattlewere already being tested halfway through the 20th century.Loosli and Warner (1957) studied the effects of maize[corn] and sorghum [milo] DGS on milk production. In theirexperiment, they compared the value of maize dried distillersgrain with solubles, maize dried distillers solubles, sorghumdried distillers grain with solubles and sorghum driedsolubles. They found no significant differences betweenDGS sources, although diets that contained DGS productsresulted in greater 4 percent-fat-corrected milk (FCM) production,as well as a greater milk fat percentage.Any grain that stores starch in its endosperm can beused to produce ethanol. The advantages of one cereal cropover the next rely on its alcohol yield per unit area, whichdepends upon the adaptation of that plant to its environment.Regardless of the grain, the process is basically thesame. Ground cereal grain is fermented in water by theyeast Saccharomyces cerevisiae, with added co-factors. Thestarch-spent mash is separated from the liquid, and ethanolis extracted from the supernatant liquid by distillation. Thenutrients remaining in the mash are concentrated to anextent determined by the amount of starch removed. Thethree energy-yielding nutrient fractions that remain for digestionby livestock are protein, structural carbohydrates and fat.Each of the first two yields essentially the same amount ofenergy as the starch removed; fat in contrast yields 2.25 timesmore energy by weight than either of the other two fractions.The net result of starch removal is a feedstuff that releasesmore energy when catabolized in the organism.Of the United States bio-refineries that use cereal grain assubstrate, maize is used as the sole cereal in 95.4 percent ofthem (Table 1). In the European Union and Canada, however,maize is used exclusively by only 34.6 and 50 percent of theplants, respectively (RFA, 2011; ePURE, 2010; CRFA, 2010).Because of its more intense agricultural practices, maize is aless sustainable cereal as substrate for ethanol production inTABLE 1Number of operational ethanol plants that use grain assubstrateMaize Wheat Other grain TotalUSA 186 0 9 195EU 9 9 8 26CANADA 8 5 3 16Total 203 14 20 237Sources: Adapted from: RFA, 2011; ePURE, 2010; CRFA, 2010.