This journal club episode comes to you from the 2024 Tri-State Dairy Nutrition Conference. The paper is “Assessing Transition Cow Health: Integrating Traditional and Novel Biomarkers” from the conference proceedings with Dr. Andres Contreras of Michigan State University.

What is a biomarker, and what makes a good biomarker? Dr. Contreras defines anything that can help assess a physiological response or pathological state. Two examples would be BHBA (beta-hydroxybutyrate) and NEFA (non-esterified fatty acids), both fat mobilization measures. (2:56)

Dr. Contreras structured the paper in three sections of biomarkers: (3:54)

1. Ones that can be measured by looking at cow records, like how many DAs or hypocalcemias occurred over a period of time.
2. Cow-side measurements like BHBA in urine or blood.
3. Samples must be sent to a lab to be measured. These generally cannot be used to make decisions immediately but can help assess how a transition program is working, for example.

How many samples should be taken, and what cows should be sampled in a commercial dairy setting? Dairy size, pen size, and pocketbook size will all play a role in this decision. Experts usually recommend at least 10 head, and those 10 must represent the cows' population in your pen. If you have the ability to take more samples, Dr. Contreras recommends 10-12% of the cows in question. He then describes ideal times before and after calving to sample BHBA and NEFA for the most predictive value. (5:31)

Setting a target that integrates BHBA and NEFA the first week after calving with measures like body condition score and/or body weight is ideal. Cows will mobilize fat post-calving no matter what, so the goal is to moderate the degree and intensity of fat mobilization. (11:38)

Rumination and activity monitors are great for measuring biomarkers in real-time and are excellent tools for diagnosing problem cows early. Dr. Contreras has researched ultrasounds to measure fat mobilization, but this may not be practical in a commercial setting. Urine pH after calving might start to be a significant predictor of clinical ketosis. Healthy cows will have a higher urine pH than sick cows.  (14:44) 

A transition cow experiences several types of adaptations: lipid mobilization to address negative energy balance, skeletal muscle mobilization to address negative protein/amino acid balance, calcium mobilization to compensate for calcium loss, and oxidative stress due to generating energy. The goal is to target biomarkers that reflect the intensity of those adaptive mechanisms. Many of these require sending samples to a lab. A dairy’s nutritionist, veterinarian, and farm manager work together to create a targeted suite of biomarkers to assess their cows and reach their goals. (21:11)

Inflammation is often at the core of transition cow maladies. Measuring a panel of acute phase proteins the first week after calving and comparing the dynamics of how they occur through the year could help identify issues in closeup cows if those proteins are spiking. (26:03)

The group discusses the importance of using individual herds’ baseline data for prediction and assessment and focusing on closeup cows when fresh cow problems arise. They also discuss biomarkers for excessive protein catabolism and a liver functionality index. This leads to a discussion of whether creating an index might be a better overall measure than making decisions on just one diagnostic value. What if someday there might be one perfect predictive biomarker, and what might that look like? (27:50)

In summary, you should not rely on a single biomarker and start measuring early. Ideally, this would be in the dry period. If that’s too challenging, it would be at least a few days after cows go to the closeup pen. Cow-side biomarkers like BHBA, body condition score, and body weight can tell you a lot about transition cow health. Use all the biomarkers and herd records available to design your approach to transition cow health. (43:10)

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