FACTORS INFLUENCING THE METABOLIZABLE ENERGY VALUE OF RAPESEED MEAL: LEVEL IN DIET, EFFECTS OF STEAM-PELLETING, AGE OF CHICK, LENGTH OF TIME ON DIET, VARIETY OF RAPESEED AND OIL EXTRACTION PROCEDURE

Abstract

Three experiments were carried out with young chicks which showed that steam-pelleting and regrinding a sample of rapeseed meal prior to its incorporation into an assay diet increased its metabolizable energy value, possibly due to improved digestion of the fibrous material in the rapeseed meal. Level of inclusion of the rapeseed meal in the assay diet did not influence the contribution of the rapeseed meal to the overall metabolizable energy of the diet. Neither the age of the chick nor the length of time that the chicks had received the rapeseed meal containing assay diets had sufficient influence on determined metabolizable energy value to account for the wide discrepancies found between published reports of the metabolizable energy value of rapeseed meal. Ten samples of rapeseed meal which had been prepared from either B. napus or B. campestris cultivars by the all solvent, the pre-press solvent or the expeller process were examined. All 10 samples were fed to young chicks and 5 of these samples were fed to mature roosters. The metabolizable energy values of the B. napus meals were very similar for both types of birds, but for the B. campestris the values tended to be higher for the roosters. In these experiments, nitrogen-corrected metabolizable energy values of from 1.34 to 2.00 kcal/g were found; half of this variation could be attributed to variation in fat content of the meals.