We’ve heard a lot of buzz over the last couple years about subclinical ketosis in fresh cows, different methods for testing and how subclinical ketosis affects cows. In the spring of 2012, we started an on-farm survey to determine the level of subclinical ketosis present in several Upper Midwest herds using Abbott’s Precision Xtra blood meter.

This meter has very high sensitivity and specificity compared to other cow-side ketosis testing methods currently available. Our objectives were to not only find out how much subclinical ketosis is out there, but also determine if the Precision Xtra meter was an effective and easy-to-use on-farm tool.

At freshening, a cow’s dry matter intake is already at a low point, and the increased energy demand of lactation outpaces the energy she is consuming, consequently pushing her into a negative energy balance.

In order for her to meet the increased energy demands of lactation, she must mobilize body fat. This in and of itself is not a bad thing; all cows go through this negative energy balance state for a period of time.

The problem arises when a cow is forced to mobilize too much body fat to meet energy demands, resulting in more fat entering the liver than can effectively be metabolized completely. This leads to the formation of ketone bodies, which circulate in the bloodstream.

One of the ketone bodies produced is beta-hydroxybutyric acid (BHBA), which can be easily measured using the blood meter and used as an indicator of ketosis status.

Subclinical ketosis is defined as increased levels of circulating ketone bodies without the presence of clinical signs of ketosis.

Unlike clinical ketosis, subclinical ketosis cannot be diagnosed by outward signs and symptoms, and therefore subclinical ketosis-affected cows go unidentified and untreated unless blood, milk or urine tests are conducted.

Studies have demonstrated cows with bouts of subclinical ketosis in early lactation are at greater risk for displaced abomasum, metritis, clinical ketosis, reduced reproductive performance and often lower milk production.

The costs associated with these events reduce the overall profitability of a dairy. In fact, a 2001 study estimated each case of subclinical ketosis costs a farm about $78. Therefore, in addition to improved health in fresh cows, evaluating the prevalence of subclinical ketosis in your herd comes with good financial incentives.

Our subclinical ketosis survey was conducted during a 10-month time period from March through December 2012. We conducted the survey on 18 dairy farms located in Iowa, Minnesota and South Dakota.

The farms ranged from 500 to 4,500 cows – and although most of the farms milked primarily Holsteins, one farm had all Jerseys, and one farm was mostly crossbred.

For safety and tracking purposes, farms enrolled in our survey needed to have headlocks in the fresh pen and have either DairyComp 305 or PC Dart records.

Through that time frame, we tested 1,164 cows using the meter. The handheld meter requires only a very small droplet of blood placed on the test strip, which was easily attained from the tail vein.

Once blood is applied to the strip, the meter displays a result in 10 seconds. Another benefit of the meter is that you can determine the exact degree of ketosis each cow has, allowing you to choose the most appropriate treatment strategy.

We tested only mature cows ranging from two to 15 days in milk. We tested cows in groups of 12 or 24 cows and took three sample sets of cows on each farm roughly two weeks apart. This ensured we would never test the same cow twice.

Any cow at or above 1.2 mmol per L was considered to have subclinical ketosis and cows above 3 mmol per L blood BHBA were considered clinically ketotic.

Herd metabolic risk was defined as low risk (zero to one cow per 12 tested) or high risk (two or more cows per 12 tested).

Further examination of management protocols, environment and nutrition was recommended for herds classified with high metabolic risk.

Our survey revealed that 251 of the 1,164 cows tested were either subclinically or clinically ketotic (2.3 percent of the cows tested were clinically ketotic).

This resulted in a subclinical ketosis prevalence rate of 21.6 percent on a cow basis and a 55.5 percent prevalence on a herd basis.

Ten out of the 18 herds had a prevalence rate of greater than 16 percent. The herd prevalence rate range was quite dramatic in our survey; the lowest herd prevalence rate we found was 5 percent and the highest was 51 percent.

Cows with either subclinical ketosis or clinical ketosis tended to have a 31-day longer calving interval and about a six-day longer dry period.

They also tended to have a higher body condition score (BCS).

Cows that had no subclinical ketosis averaged a 3.27 BCS, while the cows that were subclinically or clinically ketotic averaged a 3.51 BCS.

After compiling all the data, we came across several interesting points when we compared cows that were subclinically ketotic either from days two to seven or days eight to 15.

What we found was that cows that were subclinical during days two to seven had a higher body condition score (3.53 BCS) than those that were subclinical from days eight to 15 (3.38 BCS).

We also looked at nine-week milk weights on these cows and compared the two groups.

Nine-week milk weights for the cows with subclinical ketosis during days two to seven averaged 105 pounds of milk, and the cows that were subclinically ketotic during days eight to 15 averaged 111 pounds of milk.

This is a six-pound difference on nine-week milk weights for cows that were ketotic during their first or second week of lactation.

Throughout our survey, we found that the meter was easy to use and quick for getting results. We were able to test these groups of cows in a very minimal amount of time (it took us less than 10 minutes to check 12 cows when they were locked up for the daily fresh-cow checks).

Therefore, we recommend using the meter as a tool to incorporate into regular fresh-cow checks on your farm. This will help you not only monitor prevalence of subclinical ketosis but also determine a more effective treatment protocol for your ketotic cows.

References omitted due to space but are available upon request. Click here to email an editor.