THE EFFECTS OF LEVELS OF ISOLATION, OR VARIETAL DIFFERENCES IN, HIGH FIBRE HULL FRACTION OF LOW GLUCOSINOLATE RAPESEED MEALS ON RAT OR PIG PERFORMANCE

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Abstract
Forty-eight crossbred pigs of average initial weight 21 kg were fed 10% Tower rapeseed meal (RSM) and 10% Candle RSM as partial replacements for soybean meal (SBM). Diets were formulated to be isocaloric. Pigs fed the SBM diet consumed less feed, gained significantly (P < 0.01) faster and were more efficient at converting feed to gain than those fed the RSM diets. Performance of pigs fed Candle RSM was not significantly different to that obtained with Tower RSM. In a second experiment, dehulled Tower RSM and Tower RSM hulls were mixed in amounts to produce RSM with crude fibre levels of 6.8, 10.8, 13.5 and 15.8%. The simulated RSM and Tower and Candle RSM were used to completely replace SBM in the diets of weanling (75 g) Sprague-Dawley rats. Rats fed SBM had significantly (P < 0.05) higher average daily gain (ADG) than those fed Tower or Candle RSM, or diets containing the rapeseed meats. There was no significant (P < 0.05) difference in ADG, feed intake or feed to gain ratio of rats fed either Tower or Candle RSM. Feed intake, feed to gain ratio and fecal volatile fatty acid concentrations increased while average daily gain decreased with increasing level of hulls in simulated RSM diets. There was no significant difference (P < 0.05) in thyroid weight between rats fed SBM, Tower RSM or Candle RSM.