The effect of different grinding and thermal treatment procedures of rapeseed on feed value for growing pigs

Digestibility experiments with pigs at 60-70 kg live weight were conducted according to the difference method to study the effects of different grinding methods on digestibility of nutrients and metabolizable energy content of full fat rapeseed. Rapeseed was ground on a roller mill with a coarse or fine adjustment or ground on a flake mill to give meals with average particle diameters of 1.04 0.39 or 0.56 mm, respectively. Furthermore, the influence of different thermal treatments (micronizer, 105 degrees C and 125 degrees C, jet sploder, 105 degrees C and 125 degrees C, hydrothermal conditioning, 98 degrees C and 105 degrees C) on reduction of glucosinolates and on digestibility of nutrients of rapeseed was tested. Digestibility of organic matter of 78 % and metabolizable energy contents of 19.2 and 20.4 MJ ME/kg dry matter were attained by feeding of thoroughly ground rapeseed (flake mill and fine adjusted roller mill, respectively). Digestibility was decreased by 13 % units and ME content by approximately 3 MJ/kg dry matter by coarse adjusted roller mill. The thermal treatments, especially the hydrothermal procedure, reduced the glucosinolate content bur the effects on nutrient digestibility and ME content were not always consistent. Rapeseed treated with the micronizer at 105 degrees C tended to increase the feed value.