Urine pH testing has been used for decades as a management tool to successfully feed a prepartum negative Dietary Cation Anion Difference (DCAD) diet. But why?
Urine pH testing is one of the easiest cow-side tests in the dairy industry. Other blood, milk, tissue, or urine metabolite monitoring practices require sample containers, shipping to a laboratory, waiting for results and interpretation. Urine pH testing provides immediate, direct insight into what is happening to the acid-base status of the cow. The costs are minimal, requiring only a few pieces of pH paper, and the test involves non-invasive stimulation for the cow to urinate.
What does urine pH tell us?
There is a direct relationship between urine pH and metabolic acidosis that is influenced by the dietary mineral concentrations of mainly sodium, potassium, chloride, and sulphur. The urine pH response to changes in these minerals happens in two to three days and can be continuously monitored as long as the negative DCAD programme is fed.
Urine pH testing helps assess whether a negative DCAD programme is working as intended. If you feed a yeast product to stabilise rumen pH and prevent ruminal acidosis, how do you test whether that rumen fluid has become less acidic? If you feed a mycotoxin binder, how do you measure how much of the toxin is still being absorbed by the cow? Rumen fluid and blood samples can be taken and tested, but that is invasive to the cow, costly and time consuming. The typical practice is to feed a product or strategy and wait to see if the cows benefit from it through health or production improvements.
Urine pH measurement results are immediate and allow you to know if the prepartum strategy is working before the cow calves and, if needed, correct it. Urine pH testing can be used to predict outcomes instead of just diagnosing a problem.
What if urine pH testing results fall outside the intended target range?
If the average urine pH is too high or low based on your targeted range, this information can be used to adjust the inclusion rate of the anion source in the diet. This allows us to “listen” to the cow and gives us time to adjust the diet to meet the desired urine pH target.
If variation in urine pH continues to occur, it then opens the door to discovering unexpected feed management errors, which typically impact not only the transition group but the entire herd. Knowing a problem exists is the first step in correcting the inconsistencies before they have a chance to negatively impact the cow.
The feedback of fluctuating urine pH in the prepartum period can indicate problems associated with the following:
• Forage particle size, which can contribute to excessive sorting.
• Under- or over-mixing related to mixer errors.
• Cows running out of feed, leading to slug feeding and variable intakes over time.
• An unexpected change in forage mineral levels that was not accounted for in ration formulation.
• A variety of other causes, such as opportunities related to feeding equipment maintenance and more.
The change in urine pH outside of your targeted range is an early warning sign that can be used to help identify and correct management issues before they affect not only the transition group but the entire herd.
For those who choose not to use a negative DCAD programme, it is worth considering how the success of an alternative strategy is monitored before calving. One of the key advantages of urine pH testing is that it provides direct feedback from the cow, allowing adjustments to be made before problems arise rather than relying solely on post-calving results.
Urine pH testing is an easy way to take advantage of a proven technology to make sure the cows are consuming the diet that was specifically formulated to meet their requirements. In addition, urine pH testing can be used to help fine-tune the diet.
Ultimately, monitoring the urine pH of prepartum cows allows you to catch unexpected changes in feeding management that could negatively impact the health and performance of not only your transition cows but your entire herd.
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