Ketosis is a metabolic disorder that occurs in cattle when energy demands (e.g. high milk production) exceed energy intake and result in a negative energy balance. Ketotic cows often have low blood glucose (blood sugar) concentrations.
When large amounts of body fat are utilised as an energy source to support production, fat is sometimes mobilised faster than the liver can properly metabolise it. If this situation occurs, ketone production exceeds ketone utilisation by the cow, and ketosis results.
In the beef cow, this is most likely to occur in late pregnancy when the cow's appetite is at its lowest and the energy requirement of the growing calf near its peak.
In the dairy cow, the mismatch between input and output usually occurs in the first few weeks of lactation, because the cow is not able to eat enough to match the energy lost in the milk.