The Study of Physical, Chemical Properties, and Apparent Metabolizable Energy of Glycerol in Broiler

Abstract

The study of physical properties, chemical elements, and apparent metabolizable energy (AME) of glycerol was conducted in two experiments. Experiment 1 was a survey of physical properties and chemical content of glycerol produced by 4 industrial and 5 community biodiesel factories operating in Thailand. Representative samples of refined and crude glycerol (1 liter) from each factory was collected and evaluated for color, viscosity, impurity, glycerol content, moisture content, and methanol content. Representative samples of crude glycerol from community biodiesel factories contain highly variable glycerol content (28.63 – 45.01%) and methanol content (3.86 – 20.18%), depending on the quality of raw materials and efficacy of methanol recovery. Glycerol content in crude glycerol is relatively low because of high contamination with matter organic non-glycerin (29.76 – 59.89%) and methanol content (3.86 – 20.18%).  Representative samples of refined glycerol from the four industrial factories were consistent in terms of glycerol (>99%) and methanol content (< 0.01%). Experiment 2 measured the AME of refined glycerol for broiler chickens. The AME of a representative sample of refined glycerol was determined by using a substitution method. A total of 128 male Ross308 broilers 15 days old were assigned to two dietary treatments: (1) corn-soy basal diet and (2) 90% corn-soy basal diet plus 10% refined glycerol. Celite^TM at a level of 1.5% was added to both diets as an indigestible marker. Experimental diets were offered to the birds for a total of 7 days. Excreta were collected for 3 consecutive days to evaluate the AME. The result show that the AME of refined glycerol for broiler chicken was 3,712 kcal/kg, which is similar to that of corn and approximately half of the AME for soybean oil. Therefore, refined glycerol can be used as an energy source in broiler chicken diets.