Abstract:
Animal Production in Australia ENTEROHEPATIC CIRCULATION OF VITAMIN Bg IN THE FOWL G.S. HEARD* and E.F. ANNISON* Although certain B vitamins are known to be present in rat, pig and human bile there have been no reports of the occurrence of vitamins in avian bile. The presence of vitamin Bg in bile has not been previously reported however, although Serebro et al. (1966) found that about 0.7 per cent of radioactivity from tritiated pyridoxine hydrochloride (3H-PN.HCl) injected into ligated sections of the jejunum in rats appeared in the bile after one hour. In studies with 3H-PN.HC1 in laying hens and broilers, 0.3-0.7 per cent of radioactivity injected intravenously, appeared in the alimentary tract after 24 hours, and 0.5 per cent of radioactivity introduced into ligated jejunal sections appeared in the duodenum after 30 minutes. These data were consistent with the possible enterohepatic circulation of Bg. Samples of bile, collected from immature male broilers, and from mature male and female breeding stock were analysed for vitamin B6 by microbiological and fluorometric methods. The presence of vitamin B6 in avian bile was confirmed and concentrations are presented in Table 1. Bile from mature cockerels contained significantly more B6 (PcO.05) than bile from hens fed the same diet. Bile from several other species was analysed and found to contain vitamin B6 but at concentrations only one-tenth of those determined for avian bile (see Table 1). TABLE 1 Concentrations of vitamin Bg in bile (ng/ml) Hydrolysates of avian bile contained pyridoxal (PL), pyridoxine (PN) and pyridoxamine (PM) with PL accounting for 60 per cent of total Bg. The presence of phosphorylated forms of Bg in unhydrolysed bile was also demonstrated. A significant increase in the concentrations of vitamin Bg in bile (P<O.OOl) and whole blood (P<O.OOl) from immature broilers was obtained when the diet was supplemented with 200 mg PN.HCl/kg. The higher blood level was due to an increase in the concentration of PL rather than PN, indicating an interconversion While the Bg concentration in bile during transport from the lumen of the gut. from birds fed the unsupplemented diet was lower than that in whole blood, bile from the supplemented birds contained seven times more I36 than whole blood from these birds. The nutritional significance of these findings is uncertain, but the enterohepatic contribution of B6 in birds fed normal diets is small in relation to the dietary intake of Bg. SEREBRO, H.A., SOLOMON, H.M., JOHNSON, J.H. and HENDRIN, T.R. (1966). Johns Hopkins Hosp. Bull. 119: 166. --* Department of Animal Husbandry, University of Sydney, Camden, N.S.W. 453 2570.