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Are your cows consuming more than you realize?

Keith A. Bryan for Progressive Dairy Published on 06 August 2019

In a recent article, we described forage microbial hygiene specific to nutrient preservation during the ensiling process and the subsequent potential impacts to digestion and health from the naturally occurring micro-organisms on the crop at harvest.

Although both disease-causing (pathogenic) and non-disease-causing bacteria, and fungi (yeasts and molds) can be brought in with the harvested crop or can flourish during storage or at feedout, there are plenty of potential opportunities for the TMR to acquire, and ultimately your high-producing dairy cows to ingest, these organisms or their metabolite products. So are your cows consuming more than you realize?



Byproduct and co-product feeds

Numerous studies have demonstrated the value of byproduct and co-product feeds for enhancing homegrown, high-quality forages in high-producing dairy cow diets; however, there can be challenges associated with feeding them. As the production processes for these feeds generally concentrate certain nutrients, upper limits for inclusion should be followed. Furthermore, seasonal or variable availability coupled with inconsistent nutrient content, especially moisture, can make storage and feedout difficult. This eventually leads to freshness and microbial hygiene concerns.

Depending on moisture content, byproducts like brewers grains (wet or dry), distillers dried grains, corn gluten feed and beet pulp (wet or dry) can easily become infested with spoilage fungi (e.g., yeasts and molds) and mycotoxins. Cottonseeds should be monitored for aflatoxin contamination.

Nonetheless, a silent culprit when it comes to microbial hygiene of TMR, especially in the Midwest, is liquid whey. Whey can be a disposal problem for cheese plants, making it a relatively cheap and available feedstuff, and the dry matter portion has high feeding value. The challenge isn’t storage. What could be simpler than erecting a tank to gravity flow whey into the TMR mixer wagon? The challenge is microbial hygiene. This nutrient-dense byproduct is a prime environment for E. coli and other pathogenic bacteria to grow.

I have heard of one dairy that sampled and analyzed every forage bunker and feedstuff to identify the primary source of the E. coli in the TMR and, true to form, it was the last place they looked: the whey tank. When was the last time the whey tank, pipes and hoses were cleaned and sanitized? Are your cows consuming more than you realize?

Acquired contamination

Typical acquired bacterial contamination of a TMR occurs via soil or manure. The primary soil source is mud: muddy feed areas or muddy tracks into the feed lane, whereas the primary sources of fecal contamination are birds and cows.


Soil (mud) is an excellent source of microbial contaminants. Organisms like Clostridium and pathogenic Bacilli can survive freezing, UV rays from the sun and other stressors due to their ability to sporulate – making them capable of surviving for decades or longer. Spreading of these contaminants can be as simple as equipment tires moving through muddy areas and then through feed lanes.

Birds don’t simply come to feast on the corn kernels in corn silage and then fly off. They eat and deposit a reminder they were there: feces. Bird droppings, especially from starlings, can be a significant source of pathogenic bacteria.

There are also management issues related to hygiene. Think about the cleanliness of a feed lane, cow crossover in the center of a barn and general cleanliness of the barn or feedbunks. Are we simply tracking cow manure to the feed lane when we drive through a cow crossover?

What about feed push-up? Are we pushing soil, manure and other contaminants toward cows for consumption? Regardless of source, there is a high likelihood you have some form of pathogenic bacterial contamination in your TMR.

Enterobacteria, such as Salmonella, E. coli, Klebsiella and Shigella, are organisms typically found in the intestines of humans and animals. These organisms are undesirable in TMR because they compete with beneficial bacteria for nutrients and some are pathogenic.

Although most of the Enterobacteria are regarded as non-disease-causing, some do contain a toxin that has been associated with feeding problems on dairy farms. Also, if your TMR ever gets contaminated by soil or manure, there is an increased chance it will contain one or more enterobacteria species.


Clostridium perfringens type A has been implicated in hemorrhagic bowel syndrome (HBS) as well as other digestive disturbances. The loss of cows is obvious, but what about the chronic subclinical losses that potentially occur daily without noticeable effect? Are your cows consuming more than you realize?


We all know the scenario where cows are not producing according to their diet and genetic potential. We double-check the diet on paper, and re-sample and analyze feedstuffs for nutrient content. We even go so far as to analyze the hygiene of the TMR. Still no answer or relief. What is the most important nutrient? Fresh, clean water. We know it’s fresh because when the cows drink, the bowls or troughs refill. But is it clean?

Our recent preliminary water sample survey of dairies in Minnesota and Wisconsin yielded some interesting findings. Water samples were obtained from the water trough in the high-producing pen of cows on 12 different dairies. Water samples on 11 out of 12 dairies (92%) contained coliforms above detectable and threshold levels for cows. Furthermore, water samples on seven out of 12 dairies (58%) had detectable E. coli levels that exceeded published threshold levels for cows.

Why do we continue to expect cows to produce optimally when they are constantly presented with microbial challenges? Are your cows consuming more than you realize?


We have followed silage and TMR hygiene for about four or five years and just now are starting to uncover some of the changes that occur as well as the impacts of these changes. There are numerous anti-nutritional factors in feed that compromise the optimal digestive efficiency of high-performing cows. We know numerous field-borne, storage and acquired pathogenic organisms can contaminate the TMR and water consumed by cows daily. What we don’t know is which pathogens will be present, how extensive the pathogen contamination will be or when it will happen.

Due to the uncertainties of incidence, severity and timing of pathogen challenges, logic would dictate we take a pro-active approach to prepare cows to combat these challenges. By maintaining a healthy digestive environment, we optimally prepare cows for microbial insults – whenever they might occur.

This is most effectively accomplished by feeding science-based, research-proven probiotics that provide “essential microbial support” to the natural digestive, immunological and barrier function properties of the rumen and intestinal epithelium.


Pathogenic bacteria, along with molds and yeasts, have the potential to contribute significant anti-nutritional components to TMR and water consumed by dairy cows.

Are your cows consuming more than you realize? If so, you may want to consider the positive impact of providing clean TMR and water to your cows while preparing them to effectively combat undesired microbial challenges with science-based, research-proven probiotics. The bottom line is: A healthy rumen and lower gut will naturally lead to a healthier, more productive and efficient herd.  end mark

Keith A. Bryan
  • Keith A. Bryan

  • Technical Services Manager
  • Ruminant DFM & Silage Inoculants
  • Chr. Hansen Animal Health & Nutrition
  • Email Keith A. Bryan



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