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Ketosis is a metabolic disease in cows, occurring when they are in severe negative energy balance, particularly during early lactation. The disease forms when cows can't convert mobilised body fat to energy, leading to an excess of ketone bodies. Ketosis has different types, including sudden drop in energy intake, post calving, and silage ketosis. Diagnosing ketosis includes checking for clinical signs and analysing blood BHB concentrations. It's essential to manage feed allocation and body condition scores to reduce ketosis risk. If a cow shows ketosis signs, you should consult your vet. Increase the diet's energy content or provide oral drenches for treatment. Treating subclinical ketosis using monopropylene glycol drench is not recommended in pasture-based systems.
Ketosis is a metabolic disease that occurs when the cow is in severe state of negative energy balance.
In early lactation, all cows are in a state of negative energy balance; however, the magnitude of this can vary. During severe negative energy balance, the cow mobilises excessive amounts of body fat but cannot convert this to energy through the usual pathways. Instead, ketone bodies such as β-hydroxybutyrate (BHB, also called BHBA or BOH) are produced. In small amounts, the cow can use BHB as an alternative energy source.
However, when ketone production is high, the cow cannot use all the ketone bodies for energy and BHB concentrations increase in the blood. When this occurs, the cow may suffer from ketosis.
Ketosis can be displayed in two ways:
Because clinical signs may not always be present, ketosis is often diagnosed based on the level of circulating BHB in the blood to classify cows as either clinical or sub-clinical:
However, because butyrate is a volatile fatty acid that is produced in the rumen, concentrations of BHB in the blood are also affected by diet. Blood BHB concentrations are naturally higher in cows eating a predominantly pasture-based diet, compared with those eating a diet high in grains.
Further, DairyNZ research indicates that a threshold of 1.2 mmol/L BHB in blood is not always associated with poor animal performance in a pasture-based system.
Based on this research, and because diet can influence blood BHB concentration, we recommend that:
Ketosis can be prevented by managing feed allocation and BCS (both pre and post-calving) and by paying attention to cow behaviour and adverse weather conditions. Ensure feed supply meets feed demand.
Management strategies to reduce the risk of ketosis
Rumensin™ contains monensin sodium, which alters the rumen microbial population to increase production of propionate relative to butyrate. Rumensin™ lowers blood BHB concentrations and may reduce the risk of ketosis in grazing dairy cows; however, it does not improve BCS or reproductive performance.
If a cow shows clinical signs of ketosis, seek advice from your vet. Successful treatment of clinical ketosis will involve providing cows with oral drenches or drugs that stimulate an increase in blood glucose.
Treatments that have been used in severely affected cows include intravenous metabolic solutions (e.g. 4-in-1; Ca, Mg, P, glucose), intravenous dextrose and multivitamin injections.
If the affected animal is still able to stand, increase energy content of the diet supported by oral drenching (twice daily) of glucose precursors such as monopropylene glycol (e.g. KetolTM).
If the animal is not able to stand:
Recent US studies indicate that using monopropylene glycol drench to treat housed cows with elevated blood BHB (≥ 1.2 mmol/L) improves their metabolic status, survival, and reproduction.
However, DairyNZ research indicates that although this strategy reduces blood BHB, the effects vary between herds under pasture-based systems, and in some cases reproductive performance may actually be reduced.
Therefore, using a threshold of 1.2 mmol/L BHB in blood to treat cows with monopropylene glycol drench (without other symptoms of metabolic illness) is not recommended to improve cow performance in pasture-based systems.