Is Subclinical Ketosis Draining Your Profits?

Clinical ketosis is easily identifiable, with affected cows showing rapid condition loss, a significant drop in milk yield and reduced appetite. These cows will also have an acetone odour in their breath and urine. This condition tends to occur within the first 6-8 weeks of lactation from poor energy supply around peak yield. However, cows experiencing subclinical ketosis (SCK) will not show any of the obvious clinical signs but will still have suboptimal performance with lower milk yield and reproductive performance and are still at risk of other health issues, contributing to significant economic losses.

This article will give you an overview of how to identify the signs in your dairy herd, as well as how to prevent SCK.

Subclinical Ketosis: Risks And Signs

Cows with SCK are most likely to have had fatty liver disease at the start of lactation, which may have even developed during the dry period due to excessive body fat mobilisation. The risk period for SCK is usually within the first two weeks after calving and cows/heifers in a body condition score of 4 or more at calving are most at risk.

Given the recent hot weather, which will have impacted cows by supressing feed intake, the summer months may be a higher risk for SCK, and breed can also be a factor, with Jerseys said to have a higher prevalence that Holsteins.

While the signs of SCK may not be obvious, these cows are much more likely to develop displaced abomasum (DA), and the earlier in lactation the condition occurs, the greater the risk for a DA. SCK cows are also more likely to develop other conditions as shown in the table below:

 

Table 1. Risk of cows with SCK going on to develop other conditions:

 

Condition	Odds of developing
Metritis	1.1 – 7.2x
Endometritis	1.4x
Clinical ketosis	4 – 6x
Displaced abomasum	3 – 19x
Less likely to conceive at 1st service	1.2 – 1.7x

References for risk factors available on request

 

How to detect SCK

Without obvious signs it can be difficult to diagnose SCK, and it is worth going to the effort to monitor fresh cows so that nutritional changes can be made to help improve energy balance in early lactation. The following tools are a useful guide:

1. Cowside tests for ketones in milk or urine – these include dipstick tests which indicate the degree of ketosis with a colour change.
2. A cowside meter can also be used with a blood sample to test for the ketone beta-hydroxybutyrate (BHB). However, the vet has to take the blood sample to check through the meter.
3. Metabolic profiling. Blood sampling pre- and post-calving can be used to detect BHB levels, as well as other indicators of energy status – NEFA’s (non-esterified fatty acids) and glucose. High NEFA’s indicate body fat mobilisation over a short-term period of around two weeks. For more information on metabolic profiling, speak to your vet. It is also useful to assess protein and key mineral status.
4. Milk composition – the fat to protein ratio (available from milk recording data) in individual cows can be a useful indicator. A high fat and low protein will be indicative of ketosis, with some fatty acids from body fat breakdown ending up in milk and lack of energy also potentially lowering milk protein. A fat to protein ratio greater than 1.4 is indicative of ketosis. Conversely, a low fat percentage in milk will lower the ratio and could indicate subclinical acidosis (with a milk fat to protein ratio less than 1.1).

SCK Prevention

Prevention of SCK is very much down to nutritional management and cows being in the correct body condition score at drying off, which should be maintained until calving. Both nutrition during the dry period and in early lactation is critical to minimise condition loss. Other influencing factors include having sufficient feed space for all cows to eat at once, reducing stress and taking steps to mitigate the effects of heat stress.

Ketosis can also develop as a result of feeding wet and poorly fermented high butyric acid silages. Silages with a butyric acid content over 0.5% (or 5g/kg) of dry matter should be avoided for transition cows. Some laboratories do not report butyric acid levels and report VFA’s, a combination of fermentation acids (acetic, propionic and butyric). However, high VFA silages that are very wet, with a rank, rancid or sometimes fishy smell will be high in butyric acid, and these should be fed at low levels in combination with drier, sweeter smelling and more palatable silages.

If you have further questions, the FAS advice line offers free support. Call 0300 323 0161 or email advice@fas.scot

lorna.macpherson@sac.co.uk