Biofuel co-products as livestock feed - Opportunities and challenges

Feeding biofuel co-products to dairy cattle 145tate leaf protein. Efficiencies of extraction were similarfor fresh and stored grasses, which were both higherthan for wilted grass. Leaf CP concentrations (g/kg DM)were approximately twice that of the original grass for allchemical and heat treatment combinations. In vitro degradationof OG leaf protein was evaluated using enzymesextracted from rumens of lactating dairy cows. Fresh OGleaf protein treated with HCl + Zn salts at 140 °C hadthe greatest reduction in degradation compared withHCl control. There was an effect of conservation methodon HCl + Zn salts 140 °C treated OG leaf protein, withsimilar degradability for stored (51.5 g/kg CP) and wilted(83.0 g/kg CP), which were higher than fresh (16.8 g/kgCP) after incubation for 4 hours. The authors concludedthat leaf protein from fresh grass is most suitable becauseproteolysis during storage or wilting probably decreasesits recovery and increases ruminal degradation, and bothzinc salts and heat treatments decrease degradability ofOG leaf protein within the rumen.Scott et al. (2011) recently demonstrated similarresults of increased nitrogen content, decreased NDF andimproved fibre digestibility of reed canary grass hay, timothyhay, alfalfa hay, maize stover and barley straw withthe AFEX, or AFEX followed by enzymatic hydrolysis andseparation of the soluble sugars for ethanol production.The remaining solid co-product contained increased Nand improved degradability of DM, NDF and total N in therumen, as demonstrated via in sacco experiments.KNOWLEDGE GAPS AND FUTURE RESEARCHNEEDSMuch research on new biofuel co-products has been conductedover the past decade. The goal of this researchhas been to determine optimal inclusion rates undervarious management and nutritional regimens. For practicalapplication in the field, nutritionists and producers needadditional information on how best to manage biofuel coproductsfor dairy cattle. These knowledge gaps and futureresearch needs include:• What is the optimal inclusion rate of biofuel co-productswith different types of forages? Much of the researchhas been conducted with stored maize silage andalfalfa hay, but many other forage combinations exist.Distillers grain has been demonstrated as an excellentcomplement to fibrous residues (Anderson et al., 2010)in growing dairy heifer diets. Further investigation isneeded around the world to determine how biofuelco-products supplement fibrous residues in differentproduction systems.• What is the effect of biofuel co-products on milk composition?Past research has demonstrated that biofuelco-products can have a significant impact on milk composition.Much of this is related to ruminal fermentationand digestion. More research is needed to determinethe effect of biofuel co-products on ruminal digestion,microbial protein synthesis and intestinal nutrient digestion,and how these affect milk composition with differenttypes of diets.• What is the impact of feeding biofuel co-products onnutrient digestion in dairy cattle? Limited research hasbeen conducted to determine the impact on digestion offeeding biofuel co-products and subsequent excretion ofnutrients to the environment. Excretion of certain minerals,such as phosphorus, is a concern in regions withintensive animal agriculture. Effects on greenhouse gasemissions also need investigation.• Can variability of nutrient composition of co-productsbe reduced? Nutrient composition can vary considerablyamong different production plants. These differencescan be attributed to factors such as the grain type, grainquality, milling process, fermentation process, waterquality, drying temperature and the amount of solublesblended back to the distillers grain before drying. Lackof adjustment for changes in nutrient composition canresult in diets not being formulated as intended. Thesechanges can result in reduced animal performance.• What is the effect on animal performance of interactionwith other feeds of nutrients provided in ethanol co-products?High levels of polyunsaturated fat in combinationwith highly fermentable feeds and low effective fibre cannegatively affect rumen fermentation. More work is neededto determine how biofuel co-products can be incorporatedinto diets without negatively affecting performance.• What is the impact of feeding biofuel co-products onamino acid formulation? Diets high in maize co-productsoften result in a lysine deficiency. Further work is neededto determine amino acid availability from biofuel coproductsfor improving diet formulation for high-productiondairy cows. Fast and reliable methods to determinelysine availability need to be perfected.• There is limited research in feeding biofuel co-productsto young calves, heifers and dry cows. More work isneeded to define optimal and maximal inclusion ratesfor these categories.• On-farm research of wet co-products storage is neededto best determine how small farms can store and utilizethese co-products.• Further work is needed to determine which feeds canbe replaced by biofuel co-products to improve animalproductivity, reduce environmental impact and reducethe cost of producing milk and meat. While many ofthe co-products are used currently as protein sources, itwill become more commonplace to use them to replaceenergy feeds.• What will be the nutrient composition of future biofuelco-products? Currently, many plants are removing a por-