The influence of selected technological processes on the improvement of rapeseed meal and flour feed quality part 2. effect of hydrothermal treatment and ethanol extraction on the nutritional value of rapeseed products

In experiments with rats the effect of feeding flours (dehulled and defatted seeds) and concentrates (flour extracted with ethanol) prepared from non-heated and heated seeds of low-glucosinolate rapeseed var. Jantar was studied. Flours and concentrates were fed either as the main protein supplement in cereal-based diets or as the only protein sources in semi-synthetic diets; ethanolic extracts were either administered by stomach tube or fed with the diets. Heat treatment of seeds reduced ITC + VOT contents about 27 W and did not affect phenol contents; ethanol extraction removed both ITC + VOT and phenols. Feeding the flours from heated and non-heated seeds resulted in the increase of thyroid and liver weights as compared with rats from the control group fed on soybean diet. Heat treatment of seeds improved protein digestibility of flours and concentrates and did not modify negative effect of ethanol extract on protein digestibility. Biological value of protein of flours and concentrates was not affected by heat treatment of seeds. Feeding concentrates influenced positively animal growth performance, elimenated hypertrophic effect of the flour on thyroid and liver, increased biological value of protein as compared with flour. Administration of ethanolic extracts containing ITC + VOT and phenols to rats fed on soya-bean mael diet did not induce hypertrophy of thyroid and liver similar to that observed in rats fed on flours containing these antinutritional substances. Feeding trials conducted with the new low-glucosinolate rapeseed varieties (rapeseed 00) have shown that the actual improvement of animal performance not always correlates with the decrease of the glucosinolate content in the meals. The reasons of this apparent discrepancy are not clear and studies including well defined technological treatments and analytical methods are necessary to find out the importance of residual antinutritional substances for the feeding value of rapeseed 00. Since the majority of these substances are heat-sensitive and soluble in alcohol, a study was performed with rats to establish to what extent hydrothermal treatment of rapeseed 00 and ethanol extraction of the rapeseed flour affects feed intake, growth rate and N metabolism, thyroid and liver weight of animals as well as the digestibility and biological value of rapeseed protein. The investigations were carried out as the cooperative project of the Department of Animal Nutrition of the Research Centre of Animal Production, Dummerstorf-Rostock. Federal Republic of Germany, the Centre of Agrotechnology and Veterinary Sciences of the Polish Academy of Sciences, the Academy of Agriculture and Technology in Olsztyn and the Institute of Animal Physiology and Nutrition of the Polish Academy of Sciences, Jablonna. Poland.