By David Black

Last updated 21:49, Tuesday, 12 February 2008

WE always see quite a few cases of ketosis (also known as acetonaemia or sweetbreath) at this time of year.

It is a metabolic disorder resulting from inadequate nutrient intake (especially energy) by the dairy cow in early lactation.

When blood glucose is too low, the cow mobilises body reserves, especially fat. Part of the mobilised body fat will be converted to ketones in the liver (eg acetone), which results in elevated ketone levels in the blood.

It commonly occurs 10 days to six weeks after calving in high-producing cows. Peak incidence is about three weeks.

Many high-producing dairy cows go through a sub-clinical primary ketosis in early lactation when milk production exceeds nutrient uptake and body reserve has to be used.

Underfeeding, inappetence, fat cows/fatty liver syndrome and butyric silage can all predispose to ketosis. Other problems such as retained placenta, tyre-wire disease and displaced abomasum can act as predisposing factors to secondary ketosis.

Symptoms include loss of appetite, especially to concentrates, and a sweet, pear-drop smell on the breath and subtly on the milk. Rumen inactivity appears later, but faeces appear firm and waxy. There is usually weight loss and lowered milk yield. There can also be nervous symptoms such as circling and head pressing.

Simple, cow-side tests are available to check the ketone levels in the milk and urine. There is also a blood test which measures BHB.

All treatments aim to increase blood glucose level.

Intravenous glucose injection is the fastest and most direct method, but relapses occur when it is the sole treatment. It needs to be followed by one of the longer acting treatments.

Glucocorticoids (cortisone) cause the cow’s body to produce glucose from protein tissues, but prolonged use of this hormone is not recommended.

Sodium propionate and propylene glycol are two oral sugar precursors that can be used by the cow to produce sugar in the liver. They can be fed or drenched at a rate of 250-450g per day usually following glucose or hormonal treatment.

To prevent ketosis, avoid over-conditioned cows in late lactation and dry period. Overconditioning causes depressed appetite around calving and may increase fatty liver problems. Body condition score should be 2.5-3 at calving.

A well-managed transition period and fresh cow period and well balanced rations are the keys to prevention.

Monitoring of milk quality results can be an excellent early-warning system.