Furazolidone (0.4% w/w in the feed, 10 days) reduced the feed intake and growth in 9 week old chickens, and increased the amount of
5-hydroxytryptamine (5-HT) in the brain. The
drug also increased the stimulation of
transketolase activity by
thiamine pyrophosphate (TPP) in lysed blood cells (TPP effect), and the concentrations of
pyruvate and
lactate in the blood. Experiments with pair-fed birds showed that the reduction in feed intake in
furazolidone-treated chickens could account for the reduced growth. The
drug also produced
anorexia in ducklings and turkey poults. In chickens, the
anorectic action of
furazolidone was unaffected by
methergoline (1 mg/kg, twice daily, I.M), and in ducklings
furazolidone did not consistently produce
anorexia, although it always inhibited
monoamine oxidase (
MAO) activity in the brain. These observations suggest that the
anorectic action of the
drug was not tryptaminergic in nature. The increase in the TPP effect found in preparations from
furazolidone-treated chickens was absent in preparations from pair-fed birds on unmedicated feed. Thus the TPP effect could be used as an
indicator of the effect of the
drug on the
thiamine status of chickens. However, the increase in the concentrations of
pyruvate and
lactate in blood was found both in
furazolidone-treated birds and pair-fed birds on unmedicated feed, showing that they were attributable to the reduction in feed intake. The TPP effect in
furazolidone-treated chickens, 14-49 +/- 2.33% (n = 10), was sufficient to suggest a mild deficiency of
thiamin pyrophosphate.
Thiamin, given at a dosage above the requirement of the
vitamin for chickens, did not reduce the
anorexia or the TPP effect of
furazolidone-treated birds, although it stimulated the feed intake and growth of birds on unmedicated feed. It is proposed that
furazolidone antagonized the utilization of
thiamin, perhaps by inhibiting its phosphorylation. Following the withdrawal of
furazolidone, the TPP effect returned to the control value and the rate of growth of the birds increased and matched that the controls. Thus the effect of the
drug was reversible. Addition of
furazolidone to the feed at a concentration of 0.01% w/w for 28 days did not produce
anorexia in chickens or affect the amount of
5-HT in the brain. Thus at this level, it is unlikely that the
drug would produce adverse effects in poultry.