RAPESEED MEAL AS A PARTIAL REPLACEMENT FOR SOYBEAN MEAL IN THE DIETS OF GROWING GILTS AND OF SOWS FOR UP TO THREE REPRODUCTIVE CYCLES

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Abstract
An experiment with 32 crossbred gilts averaging 10 kg at allotment was designed to evaluate prepress-solvent extracted rapeseed meal (RSM) of Brassica campestris origin as a partial replacement for soybean meal (SBM) in diets of sows during growth or growth and reproduction when the sows were retained for three reproductive cycles. Four treatments were involved: (1) sows fed SBM throughout; (2) gilts fed 6% RSM to 90 kg and SBM for the remainder of the experiment; (3) gilts fed 6% RSM to immediately prior to first mating and SBM for the remainder of the experiment; (4) sows fed 6% RSM throughout. A second experiment with 16 mature Yorkshire sows evaluated the same RSM for one reproductive cycle only as a partial replacement for SBM when introduced into the diet immediately prior to breeding. During the growing period to 90 kg, daily feed intake, gain, and feed conversion did not differ significantly for gilts fed 0 or 6% dietary rapeseed meal, daily gain averaging 0.68 kg. Digestible energy, metabolizable energy, digestible nitrogen, and nitrogen retention coefficients were not influenced by level of dietary RSM or by period (15 or 45 kg) at which digestibility studies were conducted. Gestation length, litter size, and weight at birth and weaning were not influenced by dietary treatment in either experiment. Thyroid weights and ratio of thyroid weight to body weight of representative 2-wk-old female pigs did not differ significantly between treatments. In the first experiment, there was an average disposal of 23% of the sows per reproductive cycle because of failure to breed, failure to conceive, and other causes but these removals did not appear to be associated with treatment. The overall results suggest that up to 6% RSM of the type fed is not detrimental to sow performance when the RSM is fed during growth, throughout growth and reproduction, or when introduced suddenly at the time of breeding.