EFFECT OF ALKALI TREATMENT AND AMINO ACID SUPPLEMENTATION ON THE NUTRITIVE VALUE OF YELLOW AND ORIENTAL MUSTARD MEAL FOR SWINE

Abstract

Mustard seed batches of Brassica hirta 'Sabre' and of B. juncea 'Oriental' were oil-extracted, treated with Na2CO3 solutions to provide 0, 1 and 2% Na2CO3 based on meal, heat-treated, fed to growing pigs in diets containing 16–17% protein and tested in digestibility trials. Heat treatment alone resulted in significant reductions in glucosinolate content, especially of the allyl type in B. juncea. Na2CO3 treatment reduced glucosinolate and sinapine contents by 20–40% and reduced available lysine by 15–20%. Growth responses of swine showed Oriental meal to be inferior to Sabre meal and both inferior to soybean meal. Digestibility of Sabre protein was 64%; digestibility of energy was 65%, giving 12.3 MJ digestible energy (DE) per kilogram. Digestibility of Oriental protein was 87%; digestibility of energy was 65%, giving 12.3 MJ DE/kg. The nutritional differences between the mustard meals and soybean meal were attributed to glucosinolates affecting palatability or thyroid function, since available energy, protein or lysine were not sufficiently limiting in the diets to account for the dietary responses obtained. Nitrogen-to-protein conversion factors, correcting for both the amino acid composition of the protein and for the non-protein nitrogen component, were about 4.43 and 4.95 for mustard meals and soybean meal respectively.