THE second in the series of three, free, in-depth CPD webinars on bovine ketosis, organised by Elanco Animal Health, took place at the end of February.
Paddy Gordon, director of the Shepton Veterinary Group in Somerset, presented the webinar which focused on testing for subclinical ketosis in dairy herds. Paddy gave a very relevant, informative talk on why testing for subclinical ketosis is so worthwhile, the testing options available and which cows to test.
There were lots of examples from the speaker’s own experiences and tips on how practitioners can engage farming clients in routine testing and help them understand its value.
The first part of the talk discussed the question, why test for ketosis? Testing for subclinical ketosis is not yet widely undertaken as a routine on farms; however, it is an important part of herd health medicine because of the impact of subclinical ketosis on fertility and production and its high prevalence.
Farmers may well be aware of problems such as retained placentas, metritis, cystic ovaries and changes in fat, protein milk ratios, but there is less awareness of ketosis and the fact it could be an underlying cause of such health and production issues.
It is important to test both sick and healthy cows to avoid missing mixed aetiologies and to identify herd problems as early as possible. Although subclinical ketosis is typically identified in the transition period, the speaker had seen cases when there had been dietary upset even towards the end of lactation.
Testing for sub-clinical ketosis also provides a prognostic indicator. It’s been shown that for every 0.1mmol/l increase in milk beta-hydroxy butyrate (BHB) levels at first diagnosis, there is a 1.1 times increase in the risk of the cow developing a displaced abomasum, and a 1.4 times increase in the risk of being removed from the herd.
More accurate
Blood tests for ketones using accredited laboratories provide the most accurate results; however, there is a delay before getting the results back.
On farm, that level of accuracy is of less importance whilst the benefits of instant results are much greater in terms of being able to start treatment and putting management changes in place.
Cow-side blood tests are available in the form of a blood BHB testing strip and meter, designed for human diabetic patients. This is an invasive test that requires a vet to do the testing and the meter needs to be kept warm.
More recently, Elanco Animal Health has launched Keto-test, a new, simple to use, cow-side milk testing kit for ketosis that gives immediate semiquantitative results with 83% sensitivity, 82% specificity and a good correlation to lab values.
The kit should be stored in the fridge but allowed to come up to room temperature before use. After preparing and stripping a teat, a milk sample should be collected into a plain sample pot, the testing strip dipped in for three seconds and then the excess milk shaken off.
After 60 seconds the colour of the strip should be read. A positive result is given when milk BHB levels equal or exceed 100µmmol/l.
The speaker said he had found that getting the farmer to take samples at milking time (without the vet having to be present) but then testing them himself in front of the farmer had been a good way to avoid taking up their time and also engaging them in discussion about the results.
On more progressive farms, the farmers could, in due course, start testing samples themselves and report the results back to the vet.
For herd monitoring with Ketotest, 12 cows in the transition period (between two and 21 days post-calving) should be tested. This number of animals will give an accurate reflection of prevalence (using the 100µmmol/l as the cutoff point).
Alarm point
If 25% of the cows are positive, then this is an “alarm” point at which management intervention is strongly recommended. Ideally, testing can be done at fortnightly fertility visits or for smaller herds, once monthly. Results should be recorded to monitor the herd continuously (examples of recording sheets are available from Elanco).
In summing up, Paddy said that subclinical ketosis was worth testing for because it was a good predictor of herd performance. Keto-test was a cost effective, accurate, semi-quantitative cow-side test that was easy to use for both farmers and vets.
Ideally, 12 cows that have been calved between two and 21 days should be tested to provide a herd prevalence figure.
If this is above 25%, then intervention is required to improve herd health, welfare and production.
References
McArt et al (2012) Journal of Dairy Science 95: 5,056-5,066.
Duffield, T. (2007) Peripartum metabolic monitoring. The AABP Proceedings.
Gillund, P. et al (2001) J Dairy Sci 84: 1,390-1,396.
