Ketosis: The theory
The first of this two-part series from Elanco looks at the science behind ketosis.
Elanco says treating ketosis is one of the fundamentals of dairy herd management, as it is well-known this metabolic disease is at the root of others.
The first step towards getting on top of it involves understanding mechanisms behind the disease, which David Campion from the Priory Veterinary Centre, Whithorn, Wigtownshire, says should help keep its management on track.
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He says: “We used to think of ketosis as an inevitable consequence of calving dairy cows and it is true we will always have some degree of negative energy balance. But farmers within our practice who have excellent herd management are able to keep sub-clinical rates of disease as low as 10%.”
These farmers know this because they regularly measure ketone bodies in their cows’ blood or milk, which provides an indication of cows in negative energy balance.
And their performance is all the more impressive when it is seen in the context of the national herd, where sub-clinical or ‘hidden’ ketosis occurs in about 30% of cows in the first 50 days of lactation. So, why do ketone levels go up? Mr Campion says: “It all starts in the heavily pregnant cow whose calf fills her abdomen leaving less room for her rumen and giving her less capacity to eat.
“She may well be hungry, but because her rumen is squeezed she cannot eat enough, and her feed intake is compromised further if she is stressed by other factors, such as mixing social groups.”
Energy source
The body’s response to a lack of feed is to look for an alternative energy source, so she mobilises her stores of fat which are metabolised in the liver.
“These fats are a good fuel and their breakdown involves the production of ketone bodies – themselves a source of energy.” But ketone bodies have other effects on the cow, including appetite suppression, milk yield reduction and a negative effect on fertility as the body seeks to cope with its lack of energy intake.
“Ketones have an almost toxic effect on the developing egg,” says Mr Campion.
“You have to remember the egg you want to be fertilised, about 50- 70 days after calving, is an egg which was developing about two months or so earlier, at the height of negative energy balance.”
This means the time just before and around calving is critical to fertility, so everything should be done to minimise stress and condition-loss when the egg is developing.
“The other side of the story is the issue of fatty liver which is closely linked with ketosis and the chemical pathways involved,” he says. “If too much fat is mobilised, the liver will be unable to cope and it will ultimately lose its ability to metabolise anything well.
“Around calving, the immune system is compromised and any degree of negative energy balance will exacerbate this effect, leaving her more prone to metritis, mastitis and other infectious diseases, and in the worst cases leading to her death.”
However, Mr Campion says good management – including keeping the rumen full and minimising stress – can keep ketosis under control, and he comments on a new tool which can significantly improve a potentially difficult situation.
“We now have a bolus to help manage ketosis, which has been proven to reduce incidence in 74% of cows,” he says.
“It is something I would turn to whenever I suspect a problem – perhaps in fat cows, in those with a history of the disease or in those carrying twins. It is certainly helping many of our clients keep their ketosis rates down.”
- Next month: Ketosis in practice and prevention tips
Summary
- Monitor ketone levels
- Subclinical ketosis affects 30% of cows
- Impact of ketosis wide-ranging
- Keep the rumen full
- Minimise stress
- Check with your vet if intervention is needed
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