Ketosis (or acetonaemia) is a very distinct and frequently occurring metabolic disorder in dairy cows. It is typically found in the first part of lactation period (first six weeks after parturition, in very rare cases later or at late gestation) in high producing cows or cows on a poor diet.
Ketosis may be sporadic when only some individuals are affected or endemic when many cows in the herd are affected. Occurrence of this metabolic disorder is gradual, it is related to the increased demand of energy for milk yield, energy (in a form of glucose) absorption is much lower than the demand and hypoglycemia develops in order to compensate that gluconeogenesis and fat in liver is mobilized, these processes increases the ketone body synthesis. Ketosis may be primary and secondary.
In late months of pregnancy glucose is directed to the nutrition of the developing fetus, later when the lactation starts, glucose is also directed to the formation of the milk fat and sugar (lactose). Requirement of the glucose is very high so the blood becomes low in glucose (hypoglycaemia). In ruminants glucose is produced from carbohydrates in food. In order to keep up with the increased demands gluconeogenesis increases, if the amount of suitable carbohydrate in the diet is not enough to meet the glucose needs fat decomposition dominates in organism and by-products of fatty acid oxidation becomes ketones. These ketones and the lack of blood sugar are the main cause of the disease.
Primary ketosis occurs if a cow is inadequate carbohydrate in feed, have inadequate feeding space/quantity, eat poor quality silage or high protein feed, have disturbed rumen function, disturbed overall metabolism.
When a primary problem or disease causes an upset in the digestion or metabolism of carbohydrate by the cow secondary ketosis may also occur. The primary diseases involved in this type of ketosis include displacement of the fourth stomach, peritonitis, foreign body reticulitis, mastitis, metritis, dystocia, retained placenta, milk fever and other periparturient problems, any problem reducing the cow's appetite for a length of time (e.g. lesions in the mouth, lameness), also other problems and diseases like fatty liver, lowered immunity and so on.
The clinical diagnosis of ketosis can be based on the typical clinical signs, ketone bodies in urine and/or milk, blood and also the presence of risk factors, period before calving or peak of lactation. Ketosis is characterized by loss of appetite, depression and nervous dysfunction. If there is no response to treatment, or signs of ketosis are atypical secondary ketosis may be suspected. For the treatment of the secondary ketosis, primary disease must be treated first.
There are two common types of ketosis detectable in the dairy cattle: wasting and nervous. Wasting form of ketosis is much more frequent. In some cases this form ketosis might be mild, without any notable clinical signs, only the performance and milk yield is mildly affected. The wasting form initially starts with gradual loss of appetite. Animal can display unusual appetite: eat only grass but not the silage and concentrates, and also cow may eat anything including inedible objects in their environment. As a consequence to the loss of appetite milk yield falls quickly, but not completely. Sweet acetone smell can be smelled in animal breath, and sometimes in milk. In later development of this disorder animal becomes obviously ill, unwilling to move, head is carried close to the ground, walk is unsteady, skin elasticity response is low, coat poor. Nervous form of ketosis signs starts more sudden than wasting form of this disorder. The signs often only last for a few hours. Affected cows show various signs of nervous dysfunction: strange movements of the tongue leading to incessant licking of the skin, excessive salivation, abnormal chewing movements, licking of walls, gates or metal bars, incoordination with apparent blindness and a degree of aggression, aimless wandering, walking in circles.