Our bodies rely on a series of chemical reactions that make use of the food we eat in order to provide energy and nutrients to our cells. This process is called metabolism and it is a finely tuned machine. If it goes wrong, or tips out of balance, we could end up with an excess or deficiency of a substance which in turn can cause disease. The same is true of animals.
High yielding dairy cows are particularly prone to metabolic diseases, but the problem isn’t exclusive to large herds and even smallholders may encounter issues if there is an imbalance between the food and energy demands of the animals. The most common time for a cow to be affected is in the period around calving as this is when their body is under the most stress. However some conditions can strike at any time and the symptoms will often appear and progress very quickly so it pays to be vigilant and to know how to recognise them.
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Milk fever (hypocalcaemia)
Milk fever is basically a deficiency of calcium within the body. In the later stages of pregnancy, a cow’s milk production increases and she diverts calcium from her own body into the colostrum, or first milk. This will upset the balance of calcium within the cow and can cause her to become weak.
The first symptoms can be subtle – fine muscle tremors, in-coordination and restlessness. If left untreated, the symptoms will worsen and the cow will become recumbent, lose her appetite and may bend her head back along her sides. At this point, most cases are detected and treated but if they are missed, the cow could progress to a coma and likely won’t survive. Treatment must be prompt and consists of administering a solution of calcium to the cow, normally intravenously (slowly, or the rush in calcium can, rarely, affect the heart) or sometimes under the skin.
If the diagnosis is correct, the cow will respond quickly, often standing within the hour. If she remains down, further doses of calcium can be given but she must also be nursed carefully to avoid developing ‘downer cow syndrome’ where her sheer weight can cause secondary muscle and nerve damage from prolonged pressure and mean she will not be able to stand, even once the calcium is corrected.
The key to prevention of milk fever is to pay close attention to the management and feeding of pregnant cattle in order to ensure their nutrient requirements are met. Advice can be obtained from either your veterinary surgeon or a farm animal nutritionist.
Grass staggers (hypomagnesaemia)
Grass staggers is a rare but acutely life threatening emergency which often occurs in recently calved cows out at grass, hence its name. It occurs when the magnesium levels in the body drop dangerously low due to a combination of increased demand from lactation (milk production requires magnesium as well as calcium) and low levels of magnesium in the soil and grass.
Unfortunately, the most common sign is sudden death. If observed, the cow is seen to bellow, stagger around, collapse and convulse. Treatment must be immediate and, like with milk fever, consists of supplementing the depleted mineral. Giving magnesium intravenously can be life saving but also dangerous so must be done slowly. Like calcium, it can also be given under the skin, but it will only last for a short time in the body so it is vital that the cow is encouraged to eat good quality hay or concentrates as soon as possible after the initial recovery.
Prevention is again centred around keeping a close eye on the diet, but magnesium can also be supplemented in water, as mineral licks, or as boluses that are administered into the cow’s rumen.
If you’re a diabetic or you’ve ever tried to lose weight, you may have come across the term ketosis. Ketosis is a metabolic state that occurs when there is not enough glucose available to burn for energy so the body reverts instead to burning fat. This produces chemicals called ketones which can then be used for energy. However, this state is not sustainable and can lead to severe complications if not recognised and corrected. Cattle will often suffer from ketosis shortly after calving when energy demands on the body are high. Ketosis can also happen secondarily to other diseases or conditions so monitoring and treating these as soon as possible is vital.
The symptoms of ketosis are fairly generalised and include reduced appetite, reduced milk yield, dry faeces, lethargy and sometimes a sweet smell to the breath (although, fun fact: not everyone has the genetic ability to smell ketones!). Rarely, neurological signs can develop such as weakness, wobbliness, or collapse. Ketosis can also affect the liver. Causing it to become fatty and leading to a condition known as hepatic lipidosis or “fatty liver syndrome”.
A diagnosis of ketosis is made on the basis of clinical signs, recognition of likely triggers and the presence of high levels of ketones in the blood or urine. If ketosis is suspected, the cow should be given a form of glucose, either intravenously or orally. In some cases, steroids or even insulin may be required.
Prevention is, yet again, by nutritional management. Supplying the cow with the correct feed ration in the lead up to calving and maintaining a suitable body condition score throughout her pregnancy will reduce the risk of ketosis occurring.
Cows have four stomachs, the largest of which is the rumen and is where the fermentation and storage of the food occurs. Under normal conditions, the pH, or acidity, of the rumen is maintained at a nearly neutral state of around 6.5-7. However if a cow consumes a large amount of rapidly digestible carbohydrate such as cereals, the pH will drop, becoming much more acidic. This reduces the motility of the rumen, altering the bacterial population, and causing a condition known as acidosis.
Acidosis can be seen in two forms – acute and sub-acute. Acute acidosis, as the name suggests, will happen rapidly and often causes sudden death. Sub-acute acidosis will occur transiently and cattle can recover, sometimes without anything obviously having been wrong. Symptoms include a reduced appetite, weight loss, diarrhoea, fever, and lethargy. Probably the most common reason we would see acute acidosis is in cows that have escaped and gorged themselves on a stock of cereals. Sub-acute acidosis comes about due to an imbalance within the diet the cattle are fed.
A correct ration should be buffered to help stabilise the pH, be high in fibre and any hay stalks should be left long to encourage plenty of chewing. Rumination and saliva production will significantly aid in maintaining the rumen pH.
Alongside the clinical symptoms mentioned above for each condition, metabolic diseases in cattle are closely linked with other disorders. Cows that have upsets in their metabolism are more likely to suffer with calving problems, retained foetal membranes, uterine infections, mastitis or a displaced abomasum (fourth stomach). With metabolic disorders often being just the tip of the iceberg. They may be an indication of management problems that run deeper. Because of this, they should not be treated as an individual cow problem, but as a whole herd issue.
“Let food by thy medicine and medicine be thy food”
As you’ve probably noticed, the root of all these metabolic diseases lies in nutrition – if a cow’s diet is correct, she is in a great position to remain healthy, even during stressful periods such as calving. Metabolic disease can strike any cow, not just high production dairy cows. A happy cow is a healthy cow, so by feeding a balanced diet and keeping stress to a minimum, the risk is lowered, but stay alert and act quickly if you suspect a problem.
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