Westpoint Farm Vet’s Tim Potter tackles ketosis – a costly production disease that impacts a large proportion of UK dairy herds.
Ketosis is one of the most significant ‘hidden’ diseases impacting UK dairy herds, with around 30% of cows estimated to be affected by either clinical or sub-clinical disease. The less common clinical form of ketosis sees cows exhibiting a range of ‘strange’ behaviours including head-pressing, twitching, excessive licking and being uncharacteristically nervous of their surroundings. This is frequently referred to as ‘nervous ketosis’. Sub-clinical disease is more typical with signs including reduced feed intakes, milk yield drop, and poor fertility. Both forms of ketosis, which is also known as acetonemia, have a significant economic impact on the herd. A single case of clinical ketosis is estimated to cost £595, and the average cost for a subclinical case is £125.
Negative energy balance (NEB) occurs around calving due to the ‘gap’ caused by reduced feed intake during a period when the cow’s energy requirement – for the final stages of calf growth and the onset of milk production – is increasing. In a bid to plug this gap, the cow will mobilise body fat, which releases non-esterified fatty acids (NEFAs) into the blood. And, in response to low levels of glucose, the liver metabolises the NEFAs and releases ketones. When NEB is excessive – when a cow experiences a more significant decrease in feed intakes due to lameness, disease, or management factors – her body is unable to cope with the resulting quantities of ketones. These build up in the blood, milk and urine, and this results in ketosis.
Ketosis is preventable with good nutrition and cow management. Key to prevention is maintaining and promoting feed intakes by formulating a balanced ration and focusing on feed management. Cows will naturally experience reduced dry matter intakes during the final three weeks of pregnancy, so it is important to avoid other stress factors that could further depress intakes, such as restricting access to feed or moving cows unnecessarily.
Cows carrying too much condition, with a body condition score (BCS) of more than 3.5, will have reduced appetites and will mobilise more fat, increasing their risk of ketosis. So it is important that BCS is regularly monitored throughout lactation and diets managed accordingly. Producers should aim to dry cows off at BCS 3. The dry period is too late to significantly reduce or increase body condition score. Reducing body condition in the dry period, particularly during the late dry period, may even be counterproductive and result in excessive fat mobilisation prior to calving.
Taking a holistic approach to disease management in the period immediately before and after calving is key to minimising ketosis. Cows with calving difficulties, retained membranes, endometritis, milk fever, toxic mastitis, and hypomagnesaemia are all at increased risk of ketosis. Preventing these production diseases therefore reduces the risk of ketosis.
Many producers tend to underestimate the level of ketosis in their herd. Based on the risk factors discussed, there are groups at increased risk of developing the condition. These are: cows with a BCS greater than 3.5, but also thin cows with a BCS less than 2; heifers older than 27 months at first calving; any cattle carrying twins; and cows in their third or more lactation.
That said, it is also important to understand what is going on in the rest of the herd. Routine screening using either blood or milk sampling at key stages around calving and peak lactation are excellent start points to help determine the extent and nature of any ketosis in a herd. Depending on the results, it is then possible to work with the vet and nutritionist to manage the disease and optimise dry- and transition-cow management.