Milk production places a significant burden on a dairy cow’s resources, with the majority of the energy required to produce large volumes of milk usually obtained from ingested feed and body reserves. However, when milk production increases rapidly during the early stages of a new lactation the energy taken in is often insufficient to meet the energy output required to reach peak milk production. As such the cow goes into a negative energy balance and can become more vulnerable to poor health, with any stresses that cause a further reduction in feed intake potentially leading to the additional health problems.
A negative energy balance leads to the mobilisation of free fatty acids and glycerol from the fat stores which are oxidized into products such as Acetyl-CoA. However, the liver cannot fully process all that Acetyl-CoA and the excess is therefore converted into, among other things, ketones – a process known as acetonaemia or ketosis.
Insufficient ruminal production of propionic acid (the main precursor of glucose in ruminants) will result in hypoglycemia and worsen the situation. This can be caused by underfeeding or a reduced feed intake as a result of a suppressed appetite or lack of feed (quality, quantity and access). A lack of appetite is normal around calving but may be worsened in the early stages of a new lactation by a poor forage quality, sudden changes in diet or excessive weight at calving.
Other common risk factors for the onset of ketosis are:
Silage with a high butyric acid loading can also promote the onset of ketosis. Silage containing high levels of butyric acid is also less palatable and will therefore be consumed in lower quantities, further exacerbating the energy imbalance.
Secondary ketosis is common and is the result of conditions such as displaced abomasum, mastitis and metritis causing a reduction in appetite during early lactation.
In areas of cobalt deficiency, ketosis may also be diagnosed in grazing cattle: rumen microbes need sufficient cobalt to enable the synthesis of vitamin B12, and it is also essential for adequate utilisation of propionic acid.
Ketosis is also common in dairy herds affected by liver fluke or fasciolosis.
Ketosis expresses in a number of ways including reduced milk yield, weight loss, reduced appetite, dull coat, breath/milk smelling of acetone (pear drops) and fever. Some cows also develop nervous signs including excessive salivation, licking and aggression.
Cows affected by subclinical ketosis (high blood serum ketone body concentrations without any of the observed clinical symptoms mentioned above) will be at increased risk of developing clinical ketosis and will also be more susceptible to displaced abomasum and reduced fertility. They may also suffer from reduced milk production. Cows with raised blood ketone levels may excrete ketones in urine and milk.
The initial aim of treatment is to restore the lack of glucose in the body. A quick-acting glucose supplement is required immediately, with follow-up treatment aimed at providing a long-term supply of glucose. Many of the long-acting corticosteroids have beneficial effects in ketosis as they help to break down muscle protein to produce glucose which immediately replenishes the depressed blood glucose levels.
The key to preventing the onset of ketosis is to maintain a good transition cow management protocol with body condition score a key factor: cows shouldn’t be excessively fat at calving as this depresses feed intakes. On a scale of 1 to 5, a BCS of 2.5-3.0 is optimal, with anything higher than 3.0 considered too fat and at greater risk of ketosis. Monitoring the body condition of dairy cows is therefore essential throughout the dry period.
The transition cow management protocol should also aim to minimise the natural tendency for cows to consume less during the last three weeks of gestation. A high fiber ration during the dry period can also help to negate the problem of reduced voluntary intake at calving, with the provision of high levels of roughage also helping to promote good rumen digestion. The key is to check the quality of the forage being used several times every year to know exactly what your cows are eating.
The overall aim during the transition period is to ease the animal from gestation to lactation by offering a highly palatable ration at calving and providing suitable accommodation. Any major dietary changes should certainly be avoided during early lactation. Roughage with a high butyric acid content should be avoided in early lactation.
Metabolic profiles using blood samples or milk samples taken from groups of dry cows and cows in early lactation can help to monitor the herd’s health and detect subclinical disease at an early stage so that any necessary dietary changes can be implemented as and when required.
Concentrates fed during lactation should be introduced in small amounts, approximately two weeks before calving, to allow adjustments of the rumen microflora. Some nutritional products including niacin, calcium propionate, sodium propionate, propylene glycol, and rumen-protected choline, may help to prevent and manage ketosis if introduced in the last 2–3 weeks of gestation, as well as during the early stages of the ensuing lactation.
Occasionally, very high-yielding cows will be susceptible to ketosis every year: a preventive drenching program of propylene glycol immediately after calving may help to avert ketosis in these problem cows.
There is also a genetic element to ketosis: the inheritability of ketosis is relatively high and there is some variation in breed predisposition to ketosis. However, management protocols have a much greater influence than genetics on the incidence of ketosis.
Alternatively, if you would like to find out more about how Animate and OmniGen can improve the health and performance of your freshly calved cows please contact us to request a free ‘Transition Assessment’ with a Phibro dairy expert who will work with you to discuss the following:
Farm Health Online. 2004. Ketosis. [ONLINE] Available at: https://www.farmhealthonline.com/disease-management/cattle-diseases/ketosis/. [Accessed 1 June 2020].
MSD Manual Veterinary Manual. 2014. Overview of Ketosis in Cattle. [ONLINE] Available at: https://www.msdvetmanual.com/metabolic-disorders/ketosis-in-cattle/overview-of-ketosis-in-cattle. [Accessed 1 June 2020].
NADIS. 2002. Acetonemia. [ONLINE] Available at: https://www.nadis.org.uk/disease-a-z/cattle/acetonaemia/. [Accessed 1 June 2020].