References
What's new in ketosis in dairy cows?
Abstract
Over the last twenty years, much has been learned about ketosis as a disease of dairy cattle. Its aetiology has been found to be more complex than it was previously thought to be, with new factors coming to light–such as the discovery that the disease actually begins in the weeks before calving – and the exploration of the risk factors and genetics of insulin resistance. The importance of abnormalities other than hyperketonaemia has been demonstrated, and a better understanding of its treatment and prevention has been gained, including the use of non-steroidal anti-inflammatories and the most suitable gluconeogenic precursors, and the selection of replacement heifers with a lower genetic predisposition to ketosis.
Ketosis causes infertility, loss of milk yield, and greater risk of other postpartum diseases. Veterinarians tend to be focused on ketones, perhaps because beta-hydroxybutyrate (BHB) is easy to measure, and acetone can be smelled on cows' breath. But ketones are not the cause of lost milk yield, and they are not a primary cause of infertility. Ketones might be a cause of the increased risk of other diseases: the mechanism for this is not known. When used without qualification, the word ‘ketosis’ herein refers both the clinical and the subclinical conditions.
Hyperketonaemia is a marker for the biochemical end stage of ketosis. However, the preceding stages are important in their own right. These stages are hypoglycaemia and a high concentration of free fatty acids (FFA, also known as non-esterified fatty acids, NEFA) in the blood.
Hypoglycaemia is important for two reasons. One is that suppression of hormone-sensitive lipase in adipose tissue by insulin is lifted, resulting in lipolysis, which releases glycerol and FFA. Hypoglycaemia is a primary driver of ketosis.
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