Ketosis is a metabolic disease which usually occurs in cows in early lactation. At this time the cow’s appetite is depressed after calving and energy intake cannot meet the increasing demand of the rising milk yield. This period of ‘negative energy balance’ is normal in all newly calved cows but it is the level at which this happens that is important.

To meet energy requirements, the cow loses weight by mobilizing back fat which is then transported (as NEFAs) to the liver and broken down to release energy. During periods of high energy demand the liver cannot fully utilize the fat and metabolites known as ketones, such as acetone and beta-hydroxybutyrate, are produced. If too much weight is lost, these ketones overflow into the blood resulting in a further depression of appetite and subsequently reduced milk yield.

Typically, cows will lose 0.5 in body condition score from calving to service but many lose more than that. Fat cows already have lower dry matter intakes post calving and so their body condition score drops even more, taking them to the point of Ketosis. Cows that have been dry for a long period of time or cows that have some sort of metabolic disease during calving, or Dystocia, are also more susceptible to Ketosis.