A Nutritional Comparison of Various Rapeseed and Mustard Seed Solvent-Extracted Meals of Different Glucosinolate Composition

Seven solvent-processed meals from Brassica napus, B. campestris and B. juncea seed, were compared with soybean meal in a replicated factorial experiment involving three levels of meal (5, 10 and 20%), with and without a flavoring mixture, with and without dietary myrosinase, in a feeding trial with male weanling mice. The addition of 0.3% myrosinase improved the digestibility of both protein and energy fractions, but resulted in growth depression in diets containing meals high, in glucosinolates and fed at 10 or 20% levels. Removal of feed intake differences by regression methods revealed that non-hydrolyzed glucosinolates in diets containing 10% Brassica meals had little effect on growth rate, except for one B. napus meal high in 2-hydroxy-3-butenyl glucosinolate. Diets containing glucosinolates giving rise to allyl- and butenyl isothiocyanates, as well as oxazolidinethione, inhibit growth; therefore, total glucosinolate content should be considered in assessing the nutritional value of Brassica meals.