Inclusion of Crude Glycerin in Diets for Sheep

Crude glycerin is the main by-product of biodiesel industry. It has a great potential for reducing the feed costs in ruminant feedlot systems without affecting animal health and performance, mainly as a replacement for conventional food energy sources, such as corn grain. In the past years, great advancements have been achieved with crude glycerin utilization. This by-product is mainly composed of glycerol, an energetic compound of great assimilation by rumen microorganisms, being extensively metabolized in the liver. Recent studies with ovine species have demonstrated that high concentrations of glycerol (more than 76% of crude glycerin) can be used without detrimental effect for animals. In the rumen, glycerol is rapidly metabolized by microorganisms to form volatile fatty acids (VFA), mainly propionate and butyrate. In this way, glycerol constitutes an excellent substrate for gluconeogenesis and animal energy generation. At present, the inclusion of up to 20% of dry matter (DM) in a total diet seems to be the most interesting strategy, as it promotes greatest animal performance. However, other studies suggest that high inclusions of crude glycerin (30% of dry matter) could be possible depending on market price and the structure of farm operation, with favorable economic results.