Researchers at the ARS Swine Odour and Manure Management Research Unit in Ames, Iowa and Iowa State University examined the effect of crude glycerin in pig and poultry diets.
Pigs fed the crude glycerin were able to digest the feed supplement efficiently, and it provided them with a supply of caloric energy that basically equalled that of corn grain. A follow-up study showed no effects on weight, carcass composition and meat quality in pigs fed diets containing 5% or 10% crude glycerin from weaning to market weight.
In the poultry study, both layers and broilers were fed different levels of crude glycerin as part of the ration. No significant differences were found among the four groups in the feeding trail when comparing feed consumption, egg production and egg weight. Feeding studies with boilers showed similar positive results.
While the initial data indicates crude glycerin is an excellent source of energy and can be used without harming animal performance, there is more to learn such as how to handle glycerin in the feed mill and possible limiting factors from residual methanol and salts left in the glycerin after biodiesel production.