Why should you care about subclinical ketosis (SCK)?
Subclinical ketosis (SCK) is defined as an elevation of ketone bodies without clinical symptoms of ketosis. SCK is associated with the occurrence of many other transition cow diseases, such as clinical ketosis, metritis, retained placenta, and left displaced abomasum (LDA).
By monitoring the herd level of SCK, producers can work to prevent these economically significant diseases.
- Subclinical ketosis is a common transition disorder encountered on all dairies.
- Most studies show us that the prevalence of the condition is anywhere from 5% to 80%.
- Usually, 15% is considered the alarm level for when you, your veterinarian, and your nutritionist should look into the transition program.
All cows suffer from a negative energy balance (NEB) around the time of calving. This occurs based on increased energy demand from milking production and decreased nutritional intake.
Most cows have reduced dry matter intake before and after calving. Reduced intake, combined with an increased demand for energy from milk production, causes the cow to use the energy stores in her own body to try to make up the difference. The cow mobilizes fat stores and sends the fat to the liver.
The liver is an amazing and complex organ, and, especially in the dairy cow, has a high workload. The liver metabolizes fat to useful components for energy, including ketones. Excessive fat mobilization to the liver can overwhelm the liver’s ability to process, and this can result in fat accumulation, leading to fatty liver (hepatic lipidosis).
The circulating ketones and circulating fat can be measured to determine the severity of the negative energy balance. The ketone that is measured is beta-hydroxybutyrate (BHBA), and the fats measured are non-esterified fatty acids (NEFA’s).
Both BHBA and NEFA measurement has been evaluated in the literature. NEFA’s are best-used pre-calving, and BHBA’s are best-used post-calving. Both sampling techniques are valuable because they allow you to identify where your most significant challenge is, either pre-calving or post-calving.
- NEFA measurement is done at a laboratory and requires a serum sample.
- Take samples from cows between 14 and 2 days before calving.
- The cut off that predicts clinical disease is 0.29 mEq/L.
- BHBA measurement can be done cow-side with ketosis meters initially developed for human diabetic monitoring.
- The literature is clear that there are differences between meters, and supports the Precision Xtra (Abbott Laboratories) meter as the most accurate when compared to the gold-standard testing.
- Using this meter, SKC is considered values greater than 1.2 mmol/L.
- Take samples from cows 3 to 14 days post-calving.
The values used for NEFA’s and BHBA were determined through research connecting these threshold values with their ability to predict clinical disease. Cows testing over the thresholds are more likely to develop diseases associated with SCK.
For example, the paper establishing the values stated that cows testing above 1.2 mmol/L BHBA post-calving were 6.7 times more likely to develop an LDA than cows testing below 1.2 mmol/L.
Post-calving BHBA levels can also be tested using milk ketone test strips. In general, these test strips are far less sensitive for detecting ketosis resulting in a high percentage of false-negatives.
The first thing to do is to make sure you have tested enough animals. In general, 12 to 15 animals need to be tested to reasonably make assumptions about the entire herd.
Several factors play into SCK, anything that would decrease dry matter intake should be addressed first. Bunk space and stocking density are critical factors for dry matter intake.
- Bunk space should be kept at a minimum of 24 inches per head and preferably 30 inches per head.
- Stocking density for free stalls should remain at one stall per cow. Bedded pack space allowance should be between 120 and 150 sq. ft. per head.
- With both systems, prioritize bunk space.
Body condition scoring (BCS) is an incredibly valuable tool. BCS has a significant impact on SCK and transition performance. Both too high and too low body conditions lead to more issues during the transition period. Cows should maintain a BCS of 2.75-3.00 out of 5 and, ideally, at least maintain their body condition post-calving.
A reduction of BCS following calving has huge implications for SCK and reproductive performance. To truly have a handle on the BCS of your cows, you should monitor routinely.
- Incorporate BCS when cows are already being handled.
- Dry off, move to close-up, calving, and move out of the fresh pen, are all excellent times to record a BCS.
- At the minimum, record BCS at the move to close up, at calving, and move out of the fresh pen. This gives roughly 21 days before calving, calving, and 14 to 40 days post-calving.
There are other causes of subclinical ketosis. Work with your veterinarian and your nutritionist to help you address the above issues and identify other possible causes.
In short, yes. Cows identified with subclinical ketosis benefit from treatment with propylene glycol. Discuss treatment protocols with your veterinarian. Most often, subclinical ketosis cows are treated with 300 ml of propylene glycol orally once per day for 3 to 5 days.
Remember, treating a condition is never as good as prevention. Do not be tempted to put a band-aid on with treatment and not work to fix the actual cause of a high percentage of SCK.
Reviewed in 2020