Glycerol as a Feed Ingredient in Dairy Rations

The term ‘bio-diesel’ is used to describe the methyl or sometimes ethyl esters produced from oilseed crops. Every 10 gallons of biodiesel produced generates about 7.6 lb of crude glycerol. According to the National Biodiesel Board, the production of biodiesel in the U.S. over the next decade is expected to grow (http:// www.biodiesel.org/). Current annual production is 395 million gallons and planned expansions in the biodiesel industry are expected to drive that capacity to more than 1.1 billion gallons within the next 18 months annually, generating more than 800 million pounds of glycerol. Corresponding price projections suggest that glycerol could be priced competitively with grains as a source of energy for livestock. The value of glycerol in this regard may be further amplified with increasing diversion of corn and other grains to ethanol production. Although there is supporting evidence for use of glycerol for transition cows, there is little information that examines the use of glycerol as a macro-ingredient in rations for lactating dairy cows. This review will explore some of the attributes and issues pertinent to glycerol as a feed for lactating dairy cows and highlight results from a recent research study at Purdue University where the value of glycerol was examined as a replacement for corn grain.