1. The changes in a number of metabolic measurements brought about by low-biotin diets associated with high and low incidences of fatty liver and kidney syndrome (FLKS) were studied in healthy 4-week-old broiler chicks.
2. Liver pyruvate carboxylase (pyruvate: CO2 ligase (ADP); EC 188.8.131.52) activity was low in birds fed on a diet causing a high incidence of FLKS but the addition of fat or protein to this diet, to decrease the incidence of FLKS, increased enzyme activity.
3. Liver weights, blood lactate concentrations, plasma lactate dehydrogenase (l-lactate:NAD oxidoreductase; EC 184.108.40.206) activities and values for C16:1:C18:0 fatty acid in liver, adipose tissue and plasma triglyceride were highest in birds fed on the high-FLKS diet and all measurements were negatively correlated with pyruvate carboxylase activity.
4. Birds with high plasma lactate dehydrogenase activity or triglyceride C16:1:C18:0 values were the most likely to develop FLKS when fasted.
5. There was no evidence that increased liver weight was associated with increased activities of certain other liver enzymes.
6. It is concluded that FLKS occurs in birds with little or no hepatic gluconeogenic capacity via pyruvate carboxylase as a result of a dietary insufficiency of biotin but that the initiation of the syndrome is probably associated with the inhibition of other pathways of gluconeogenesis.