#07-165

Complete

Date Full Report Received

01/22/2009

Date Abstract Report Received

01/22/2009

Investigation

Institution: , ,
Primary Investigator:

The objective of the proposed research was to determine the variation in metabolizable energy (ME) content of crude glycerin samples from a several biodiesel production facilities using different feedstock sources (soybean oil, animal fat, and used restaurant grease). Nursery pigs initially weighing 10.4 kg were fed dietary treatments consisting of a basal diet, or diets containing crude glycerin from various biodiesel production facilities supplemented in the diet at approximately 9.1%. Using typical energy balance techniques, each diet was fed twice daily to pigs in individual metabolism crates for a 6-d adjustment period after which a 4-d energy balance trial was conducted. Metabolizable energy for each diet was calculated by subtracting the fecal and urinary energy excretion of each pig from the gross energy consumed, with the ME value of each crude glycerol estimated by the difference between the test and the basal duet. The gross energy (GE) of the crude glycerin samples ranged from 3,173 to 6,021 kcal/kg while the determined ME ranged from 2,535 to 5,206 kcal/kg, each being a reflection of the concentration of glycerol, methanol, and free fatty acids in the crude glycerin. Prediction of each crude glycerin’s ME based upon the crude glycerin’s composition was poor. In contrast, the prediction of each crude glycerin’s GE based upon the crude glycerin’s composition high [GE kcal/kg as-is basis = -306 + (46.65 × % glycerin) + (54.31 × % methanol) + (101.83 × % fatty acids)]. Because the relationship between GE and ME was similar between all crude glycerin samples, averaging 85.4%, ME could be accurately predicted based upon the predicted GE and the average ME:GE of 85.4%. Overall, data presented herein show that the concentration of glycerin, fatty acids, and methanol affect the GE and ME of crude glycerin, and because crude glycerin is easily digested and metabolized, it can be used as a viable source of energy in growing pigs. These data also suggest that the amount of ash and methanol had little to no effect on ME utilization. However, the salt concentration of crude glycerin needs to be accounted for in feed formulation and level of methanol needs to be considered for regulatory reasons.