EFFECTS OF SODIUM AND FERROUS SALT TREATMENTS ON THE NUTRITIONAL VALUE OF YELLOW MUSTARD MEAL (B. HIRTA) FOR SWINE AND MICE

Commercially prepared meals (solvent-extracted) made from yellow mustard (Brassica hirta), Yellow Sarson (B. campestris), Tower rapeseed (B. napus) and soybean were compared in palatability preference trials with mice. Meals treated with aqueous solutions of sodium carbonate and ferrous sulphate, followed by autoclaving and drying, were also tested. The effects of processing treatments on glucosinolate levels in the meal and on amino acid composition were assessed and the more promising treatments were subjected to feeding and digestibility tests with mice or swine. Sodium carbonate at 3.8% by weight of the meal was more effective than lower levels for improving palatability. Over 85% of the glucosinolates were destroyed by any level of sodium carbonate including the zero level, indicating that the moist cooking and drying affected the glucosinolates and that the sodium carbonate acted on another component, possibly sinapine. The digestibility of protein was markedly reduced by 3.8% sodium carbonate; the losses of lysine and sulphur amino acids were extensive and dietary supplementation was necessary for improved growth of mice. Experiments with swine fed natural ingredient diets containing 15% of mustard meal, Yellow Sarson meal or Tower rapeseed meal revealed that all meals permitted near-normal growth and feed utilization. The inclusion of up to 0.6% ground rapeseed as a myrosinase source was not deleterious. Differences in responses of mice and swine to glucosinolates are discussed.