ARS | Publication request: Digestable and Metabolizable Energy of Crude Glycerol in Growing Pigs

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 2007
Publication Date: February 20, 2008
Citation: Lammers, P.J., Kerr, B.J., Weber, T.E., Dozier III, W.A., Kidd, M.T., Bregendahl, K., Honeyman, M.S. 2008. Digestable and metabolizable energy of crude glycerol in growing pigs. Journal of Animal Science. 86:602-608.

Interpretive Summary: With the rapid expansion of the bio-diesel industry (www.nbb.org), there will be substantial amounts of crude glycerol (the principal co-product of biodiesel production) that will become available for use as a livestock feedstuff. Because glycerol is a precursor to glucose via gluconeogenesis, is a backbone of fat in lipogenesis, and yields energy through the glycolytic and tricarboxylic acid pathways, determination of the energy value of crude glycerol in livestock feeds is vital. This research demonstrated that in pigs, the apparent metabolizable energy content of crude glycerol (87% glycerol) was 3,207 kcal/kg. This information is important for nutritionists at universities, feed companies, and swine production facilities for the determination of the energy value of crude glycerol for use in feed formulations, and provides a basis from which to assess its economic value.

Technical Abstract: The apparent DE and ME value of crude glycerol for growing pigs was determined in a series of 5 experiments using crude glycerol (86.95% glycerol) from a biodiesel production facility with soybean oil used as the initial feedstock (AG Processing Inc., Sergeant Bluff, IA). Dietary treatments were 0, 5, 10, or 20% glycerol addition to basal diets in Exp. 1 and 2, or 0 and 10% crude glycerol addition to the basal diets in Exp. 3, 4, and 5. Each diet was fed twice daily to pigs in individual metabolism crates. Following a 10 d adjustment period, a 5 d balance trial occurred. During the collection period, feces and urine were collected separately following each meal and stored at 0°C until analysis. The GE of each dietary treatment and samples of urine and feces from each pig were determined by adiabatic bomb calorimetry. Digestible energy of the diet was calculated by subtracting fecal energy from the GE in the feed, while ME was calculated by subtracting the urinary energy from DE. The DE and ME values of crude glycerol were estimated as the slope of the linear relationship between either DE or ME value of the experimental diet and feed intake. Averaged across all experiments, the crude glycerol (86.95% glycerol) examined in this study was found to have a DE and ME of 3,344 ± 8 and 3,207 ± 10 kcal/kg, respectively, when fed to growing pigs, thereby providing a highly available energy source for growing pigs.