Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 16, 2011
Publication Date: November 1, 2011
Citation: Dozier,III, W.A., Kerr, B.J., Branton, S.L. 2011. Apparent metabolizable energy of crude glycerin originating from different sources in broiler chickens. Poultry Science. 90:2528-2534. Interpretive Summary: Production of bio-diesel results in increased availability of crude glycerin (the principal co-product of biodiesel production) which can be used as a feedstuff in diet formulations fed to broilers. Previous reshearch has shown that crude glycerin is a viable energy source to swine and poultry, and that the chemical composition of crude glycerin can be used to predice the metabolizable energy concentration for growing swine. No such data is available for broilers. Consequently the current study was conducted to determine differences in appraent metabolizable energy concentration in growing broilers due crude glycerin composition, and determine if the chemical composition of crude glycerin could be used to predice apparent metabolicable energy. Results indicate that apparent metabolizable energy did vary widely due to crude glycerin composition, and that the chemical composition could be used to predict apparent metabolizable energy in growing broilers. This information is important for nutritionists at universities, feed companies, and broiler production facilities showing them the ability to use crude glycerol as a viable feed ingredient in diets fed to growing broilers.
Technical Abstract: An energy balance experiment was conducted to determine the AMEn, of various crude glycerins, and to generate an equation to predict AMEn of crude glycerin based upon its chemical composition. Dietary treatments consisted of a corn-soybean meal basal diet with no added glycerin or the basal diet supplemented with 6% glycerin. Crude glycerin sources were obtained from biodiesel production facilities throughout the United States, which utilized a variety of lipid products as their initial feedstock. Two identical energy balance trials were conducted. In each trial, 864 Ross × Ross 708 male broilers were fed a common starter diet until 17 d of age, followed by the 12 experimental diets (6 replicates per treatment) from 17 to 22 d of age, with a 48 h collection period occurring on d 21 and 22. Gross energy of the test ingredients, experimental diets, and excreta were determined by isoperibol bomb calorimetry. Apparent metabolizable energy values of crude glycerin were estimated by difference, whereby AMEn of the basal diet was subtracted from the complete diet containing the test ingredient. Glycerin sources were analyzed for water, methanol, free fatty acids, ash, and gross energy,with glycerin content determined by difference (100 - % methanol - % total fatty acid - % moisture - % ash). Apparent metabolizable energy of the basal diet and US Pharmacopeia grade glycerin were determined to be 3,085 and 3,662 kcal/kg, respectively, whereas the AMEn of the 10 crude glycerin sources ranged from 3,254 to 4,134 kcal/kg. Two crude glycerin sources had high levels of free fatty acids (24 and 35% vs. < 0.30%), and even though their AMEn, was higher than the other glycerin products (P < 0.01, 3,806 vs. 3,611 kcal/kg), their AMEn, as a percentage of GE was lower (P < 0.01, 65.5% vs. 97.4%). Utilizing all glycerin samples, the stepwise regression equation to predict AMEn was determined to be: AMEn, kcal/kg = 1,605 – (19.13 × % methanol) + (39.06 × % free fatty acid) + (23.47 × % glycerin), (R2 = 0.25; SE = 379; P = 0.01). These data indicate that glycerin is a good source of energy and its AMEn value is dependent upon free fatty acids, methanol, and water.