THE UTILIZATION OF LUPIN (LUPINUS, ANGUSTIFOLIUS) AND FABA BEAN GLOBULINS BY RATS IS POORER THAN OF SOYBEAN GLOBULINS OR LACTALBUMIN BUT THE NUTRITIONAL-VALUE OF LUPIN SEED MEAL IS LOWER ONLY THAN THAT OF LACTALBUMIN

The effects of dietary sweet lupin (Lupinus angustifolius, Unicrop) se ed meal or its insoluble fiber (nonstarch polysaccharides + lignin) on performance, digestibility and nitrogen utilization in growing rats w ere studied in four experiments. Globulin proteins isolated from lupin , faba bean (Vicia faba L. minor) or soybean (Glycine mar) were also i ncorporated into purified diets as replacements for lactalbumin (contr ol) and the nutritional effects were evaluated. Isocaloric, legume-bas ed diets supplemented with amino acids were used. Final weight gain, g ain:feed ratios, nitrogen retention and net protein utilization of the animals fed whole lupin meal-based diets for 10 d were inferior to th ose of controls. In contrast, adding lupin insoluble fiber to a contro l diet produced no adverse effects. Ileal starch and apparent nitrogen digestibilities, and fecal digestibility of starch in lupin-fed rats were higher than those of controls, but fecal true nitrogen digestibil ity was lower. Replacement of lactalbumin with globulin proteins from lupin or faba bean depressed food intake and protein utilization, but only performance was affected by consumption of soybean globulins. Rat s consuming lupin or faba bean globulins excreted significantly more n itrogen, particularly as urea through the urine. This did not occur in rats fed soybean globulins. Urea concentration in plasma was higher i n rats fed diets containing lupin meal or legume globulins. The concen trations of urea, arginine and ornithine in plasma increased significa ntly compared with control values after 3 to 9 h of a lupin diet. Afte r 9 h, plasma lysine was also decreased. We concluded that the main re asons for the low nutritional value of sweet lupin seed meal are likel y to be related to the chemical structure of the globulin proteins and their adverse effects on growth and nitrogen metabolism, and not to a ny known antinutritional factor or poor digestibility.