EFFECTS OF DIETARY PROTEINS AND YEAST SACCHAROMYCES-CEREVISIAE ON VITAMIN-B-6 STATUS DURING GROWTH

Male rapidly growing broiler chicks were fed a moderate (22%) or a hig h protein (30%) well-balanced diet containing yeast Saccharomyces cere visiae (2%) and consisting of soy protein isolate (Soyamin) or a purif ied amino acid mixture. The vitamin B-6 status was assessed according to the in vitro stimulated activity of aspartic aminotransferase (acti vation coefficient; AC) and pyridoxal phosphate concentrations in plas ma and erythrocytes. No weight difference was found between age-matche d control and B-6-deficient animals fed the Soyamin diet containing ye ast. None of the deficient animals presented signs of malfunctions of the central nervous system. These animals grew well and their skeletal development was normal after 6 weeks of age. Due to the presence of y east, increasing dietary protein intake did not augment the metabolic requirement for pyridoxine. The removal of yeast from the Soyamin diet provoked a severe symptomatic deficiency (AC 1.5). It seemed that yea st did more than promoting growth. It also protected against a lack of vitamin B-6: feed utilization was not impaired. The present study sho wed that a low level of 0.6 mg vitamin B-6/kg in a corn-Soyamin diet c ontaining yeast was adequate to maintain normal growth and to avoid ne urological symptoms. The pyridoxine requirement for normal growth and absence of convulsions has been reported to be approximately 3 mg/kg d iet.