RAPESEED, PEANUT AND SOYBEAN MEALS AS PROTEIN SUPPLEMENTS WITH OR WITHOUT ADDED LYSINE: BIOLOGICAL PERFORMANCE AND CARCASS CHARACTERISTICS OF PIGS AND RATS

Abstract

The supplemental values of prepress solvent-extracted rapeseed meal (RSM) from Brassica campestris cv. Span seed, solvent-extracted peanut meal (PNM) and soybean meal (SBM) with or without added lysine were compared using barley–wheat-based diets. Pietrain and crossbred-sired barrows and gilts and uncastrated male and female rats were the test species. For rate of gain with pigs, SBM, RSM and PNM ranked in that order, while for rats, PNM and SBM were similar with RSM being inferior. Partial substitution of RSM for 50 or 75% of PNM in diets of pigs tended to improve performance. Lysine addition to the PNM-supplemented diet did not significantly enhance food consumption, gain or efficiency of food conversion of rats, but there was a trend toward improvement of these criteria with pigs. No significant treatment, sex or breed differences were observed in energy digestibility or in metabolizable energy. In N retention as a percentage of intake, gilts were superior (P < 0.05) to barrows, consistent with the leaner (P < 0.05) carcasses of gilts. Sex, but not diets, influenced the thyroid weights of rats, with female thyroids being larger (P < 0.01) than those of males. Histopathology of the thyroids ranked RSM, SBM and PNM as goitrogenic in that order. The studies indicated that comparative values of protein supplements for the rat are not necessarily indicative of the comparative values of these supplements for young pigs.