Abstract
The effects of concentrates, in which glycerol plus soyabean meal replaced wheat, on physical, chemical and hygienic pellet quality characteristics were investigated. Three purities of glycerol were used, refl ecting different stages of the biodiesel production process. Glycerol inclusion levels were 50, 100 and 150 g/kg concentrate dry matter (DM). Concentrates were stored under good (15°C, 60% relative humidity) or bad (20°C, 70% relative humidity) environmental conditions and for 4 or 8 weeks. Chemical quality was only slightly affected by purity and concentration of glycerol and likewise by storage conditions or duration. Ergosterol concentration indicated that glycerol of different purity had a preserving effect. The physical quality of pellets was not affected by the purity of glycerol or by glycerol concentration of up to 150 g/kg DM. Glycerol at different purity may help to stabilize the hygienic quality of pelleted compound feeds without compromising the physical quality of pellets.
Highlights
The turn towards renewable energy sources in the European Union has increased the production of biofuel from rape seed oil, mainly in the form of rape seed oil methylester (RME) or biodiesel, leaving glycerol as a by-product (Körbitz et al, 2003)
Glycerol was registered as a feed additive (E 422) in the European Union more than 30 years ago (Anonymous, 1970) with no restrictions as to animal species and quantity added to feeds
The ten concentrates resulted from one concentrate without glycerol (Control) and three glycerol concentrations (50, 100 and 150 g/kg dry matter (DM)), each combined with glycerol of three purities
Summary
The turn towards renewable energy sources in the European Union has increased the production of biofuel from rape seed oil, mainly in the form of rape seed oil methylester (RME) or biodiesel, leaving glycerol as a by-product (Körbitz et al, 2003). If the amount of glycerol from biodiesel production exceeds the needs of pharmaceutical and chemical industries, it could be used in animal nutrition, possibly in the form of less pure and cheaper qualities. At least in part as a result of increasing biodiesel production and glycerol accumulation, glycerol was listed as a feedstuff in the “Positive List” of authorized feed materials (Normenkommission für Einzelfuttermittel im Zentralausschuss der Deutschen Landwirtschaft, 2007) which, among other objectives, was initiated to contribute to feed safety internationally (Anonymous, 1996) and nationally (Petersen and Flachowsky, 2004). Glycerol may influence physical, chemical and hygienic variables of feedstuffs It is not clear under which conditions glycerol may result in either improvement or detriment of pellet quality
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