Choose your ketosis monitoring tool

By Dr. Zach Sawall
In early lactation, cows enter negative energy balance.  This comes from increased energy demands for milk production, which can’t be met from dry matter (DM) intake.  If cows can’t adjust to this negative energy balance, excess body reserves are mobilized, leading to higher counts of nonesterified fatty acids (NEFA) and ketones, specifically beta-hydroxy butyrate (BHBA).

Subclinical ketosis affects 26 to 56 percent of cows and treatment is estimated to cost $298 per case.  Additionally, ketosis raises the risk of developing other transition diseases, and, when BHBA levels are greater than 1.4 millimoles per liter (mmol/L), the cow has a greater risk for displaced abomasum, metritis, severity of mastitis, more days to conception, and heightened risk for culling.

For these reasons, and more, dairy producers, nutritionists, and veterinarians are concerned about identifying subclinical ketosis and proactively managing risk factors instead of reactively treating sick cows.  This starts in the pre-fresh pen where it is important to minimize overcrowding, excessive pen moves, and high-energy diets that would suppress DM intake before calving.  Proper and timely foot trimming is also important.

Post-fresh checks are a good time to identify specific high-risk cows at calving.  Work at the University of Minnesota suggests cows with a body condition score greater than 3.5 with more than 16 pounds of colostrum at first milking are at higher risk.  Older cows and cows that have twins are also considered higher risk.

Match evaluation and style
At the herd level, one tool to help detect ketosis risk is the first test fat-to-protein-ratio, which monitors cows one to 30 days in milk (DIM).  It is suggested, if a herd has more than 40 percent of cows with a fat-to-protein-ratio above 1.4, it would be considered high risk for subclinical ketosis.

This tool is great to get a general idea of ketosis risk, but it isn’t helpful for identifying individual cows.  However, a team at the University of Wisconsin-Madison expanded the accuracy of herd-level ketosis prevalence monitoring with the development of the KetoMonitor™, a model that uses regression models to predict blood BHBA based on cow data and a milk sample.

At the individual cow level, many tests are available that will vary in accuracy.  Accuracy is determined by two factors:

• Sensitivity: The ability to accurately identify cows positive for ketosis as positive
• Specificity:  The ability to accurately identify cows negative for ketosis as negative.

Highly sensitive tests have a low false-negative rate, and highly specific tests have a low false-positive rate.  Milk and urine tests tend to be less sensitive (more apt to show false negatives) compared to blood tests.

The “gold standard” for ketosis tests is measuring blood BHBA concentrations, with a typical cut point at 1.2 mmol/L.  It is suggested to monitor cows for ketosis twice; once between three and 16 DIM and again between 10 and 16 DIM.

Select the right tool
Due to the accuracy and general ease of measuring blood BHBA concentrations, many producers have chosen to test cows for ketosis with cowside meters.  The meter of choice has been the Precision Xtra^® meter, but, due to the limited supply of strips and recent price increase, many producers have explored other options.

The other meters we have seen producers using include TaiDoc, Nova Vet and Nova Max^®.  The sensitivity and specificity of these meters are noted in Table 1.

With a few best management practices, the accuracy of these meters can be improved.  Calibrating the meters, warming up the samples, and wicking the blood sample onto the test strip instead of squirting the blood on the strip can all increase the accuracy of these meters.

It is best to identify and treat high-risk cows early, and using a cowside meter to measure BHBA concentration is one of the best ways to identify individual cows for subclinical ketosis.  Knowing your herd’s risk and the status of individual cows can help reduce ketosis and associated issues on your farm.

This article was originally written for the August 10, 2017 issue of Hoard’s Dairyman.

About the author:  Dr. Zachary Sawall grew up on a dairy farm in northeast Wisconsin. He attended the University of Minnesota where he earned his bachelor’s degree in animal science with an emphasis in ruminant nutrition. In 2013, Sawall was named Outstanding Master’s Student by the Department of Animal Science at the University of Minnesota.  He continued there to earn his Ph.D. in ruminant nutrition.  Sawall joined Vita Plus in 2015 as a dairy nutritionist and technical services specialist in central Wisconsin. In his free time, Sawall enjoys hiking, hunting, and spending time with his wife, Sandra, and their children, and working on their parents’ dairy farms.