COMPARISON OF LOW GLUCOSINOLATE RAPESEED MEAL, COMMERCIAL RAPESEED MEAL AND SOYBEAN MEAL AS PROTEIN SUPPLEMENTS FOR GROWING PIGS

Abstract

Thirty-six crossbred pigs, equally divided between gilts and barrows, were fed from an average of 6 wk of age to market weight on three dietary treatments. Isonitrogenous, isocaloric diets were supplemented with either soybean meal (SBM), low glucosinolate rapeseed meal (RSM) from Brassica napus cv. Bronowski or commercial RSM of B. campestris origin. Metabolic studies were conducted at average weights of 14 and 31 kg and there were no significant differences in coefficients for digestible energy, metabolizable energy, digestible nitrogen or nitrogen retention between treatments, between sexes, or between periods. During the first 6 wk of the experiment and for the overall experiment, there was a difference between sexes in their response to low glucosinolate RSM. Barrows gained at a similar rate when fed diets supplemented with either SBM or low glucosinolate RSM, but more slowly on diets supplemented with commercial RSM. Gilts gained more slowly when fed either RSM than when fed a SBM-supplemented diet. The results suggest that there may be a factor, other than glucosinolates, present in RSM that tends to depress performance of gilts but not of barrows. This depression arising from either source of RSM was not associated with digestibility of energy or nitrogen or with nitrogen retention.