An attempt was made to improve the nutritive value of lucerne juice as a protein source for rats. Diets, based on ground barley and lucerne juice, were supplemented with amino acids (methionine andlor lysine), polyethylene glycol (to neutralise phenolic compounds), cholesterol (to neutralise saponins), or fat. In one diet the content of calcium and potassium was lowered. Aerobic fermentation of juice with or without yeasts was also carried out. The biological value ( B V ) and true digestibility ( T D ) of proteins were estimated using the Thomas-Mitchell balance method. The amino acid supplement improved the BV of protein )om 52 to 57 as a result of its supplementary eflect on barley rather than juice protein. The addition of polyethylene glycol (PEG) had an adverse eflect on the nutritive value of the mixture (BV was reduced ffom 48 to 39). The BV of proteins was slightly lowered by aerobic fermentation with or without yeasts (control 42, 41 and 37, respectively) but dgerences were not statistically significant.
The eftect of lucerne juice and casein on apparent digestibility of basal nutrients was also compared. Lucerne juice had an adverse efSect on digestibility of all nutrients, especially fibre, and on availability of minerals, which may have been caused by changes in the caecum of the rats.