Vitamin B6 Requirement of the Mink ,

Abstract

The requirement and metabolism of vitamin B6 were investigated with growing mink. Purified diets containing zero, 0.75, 1.5, 3.0 and 6.0 mg/kg of vitamin B6 (pyridoxine·HCl) were fed to 50 pastel mink kits. Mink receiving no vitamin B6 showed deficiency symptoms (ataxia, acrodynia, convulsions, irritability and apathy) terminating in death unless relieved by supplementary vitamin B6. Groups receiving diets containing 0.75 mg/kg of vitamin B6 showed growth comparable to those on higher levels but developed some abnormal symptoms. In a further study 75 pastel male mink kits were fed purified diets containing zero, 0.4, 0.8, 1.6, and 3.2 mg/kg of vitamin B6. Mink receiving the zero, 0.4 and 0.8 levels of vitamin B6 showed deficiency symptoms. The group receiving 0.8 mg/kg showed growth comparable to the higher groups; however, only 9 animals out of 15 survived at 20 weeks of age. Forty male mink were used in two metabolism studies in which urinary xanthurenic acid, kynurenic acid and N1-methylnicotinamide were measured. Urinary excretion of xanthurenic and kynurenic acids was sharply elevated following the ingestion of 2.5 mmoles L-tryptophan during vitamin B6 depletion. Supplementation with 0.8 mg/kg of vitamin B6 brought about a slight reduction in the urinary excretion of xanthurenic and kynurenic acids while the addition of 1.6 and 3.2 mg/kg brought about an immediate return to predepletion levels. Urinary excretion of N1-methylnicotinamide was slightly increased following the ingestion of tryptophan in all dietary treatments. The lowest dietary level of vitamin B6 which promoted growth and prevented abnormal symptoms and abnormal tryptophan metabolism was 1.6 mg/kg.