Mycotoxins and bacterial endotoxins are common in many U.S. dairy farming environments, and without effective in-feed mitigation strategies, milk production is becoming ever more challenging. Volac’s technical business manager for North America, Bryan Miller, discusses the additive threat dairy farmers now face.

Mycotoxins are secondary metabolites produced by molds on animal feedstuffs that possess the potential to derail efficient milk production from dairy cattle. Mycotoxins are often present in grains, nuts and oilseeds, and other primary raw materials in animal feed formulations. Adverse impacts include lost milk, poor growth rates in youngstock, depressed animal health and even fertility challenges.

Fungal mycotoxin production in feed materials, such as grains, is catalysed by the presence of warm, dry growing conditions; and some mycotoxin producing fungi grow well in cool, wet situations. Stress factors, other than weather, can also increase the production of mycotoxins. Although there are certainly other undiscovered mycotoxins, those known to cause significant challenges to optimal animal production generally include aflatoxins, ochratoxin A, deoxynivalenol (DON), zearalenone and fumonisin(s).

There is no doubt that mycotoxin prevalence is increasing globally; common toxins previously only found in certain parts of the world are now being discovered in other areas. This is in part due to a better analysis and surveillance of raw materials but also because of climate change. For example, aflatoxin – a common mycotoxin produced by Aspergillus fungi that is usually found in hotter climates, is now also being detected in more northern geographies.

Ruminant animals are better able to deal with aflatoxins, although there is understandable concern about the potential of carryover of the major metabolite of aflatoxin (aflatoxin M1) into milk and its carcinogenic effect in humans. Consequently, there are regulated limits worldwide for aflatoxins in feed.

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There is also increasing concern about the impact of the additive effect of mycotoxins on dairy cattle if the animal is also being exposed to a significant endotoxin challenge from its environment.

Endotoxins: LPS challenge and the inflammatory response

Endotoxins are toxins produced from gram-positive bacteria, with lipopolysaccharide (LPS) in their cell walls. At times of stress – or in the context of acidosis, when the gut wall becomes more permeable – LPS can cross from the rumen into the lumen of the gut. A potent stimulator of the immune system, LPS is a pathogen associated molecular pattern (PAMP), that causes a Toll-like Receptor 4 (TLR4) mediated inflammatory response. When LPS crosses the barrier of the gut, a local inflammatory response will be stimulated. In worse cases, the LPS will enter the blood stream and in the inflammatory response can become systemic.

This inflammatory response is a necessary defense mechanism designed to protect the body from infection. However, when triggered repeatedly or excessively, as in cases of leaky gut, it can become harmful to the animal's health. During an incidence of acidosis, there is an increased level of free endotoxin in the rumen due to an increased turnover of the microbial population, and so the challenge of LPS is greater.

Fueling the immune system: The energetic cost of inflammation

The inflammatory response is a biological function that requires energy. Activated immune cells, such as macrophages, require glucose to mount the inflammatory response. This energetic requirement is a must from a biological survival standpoint, and so energy is diverted from other biological needs such as performance in milk production or average daily gain. Work has shown that in a Holstein dairy cow, the energy requirement to fuel an active immune response, is around 2 kilograms (4.4 pounds) of glucose per day. That equates to 8.4 megacalories (Mcal) of energy per day, or 7 kilograms (15.4 pounds) of milk. Often when we make changes to diets, we are looking to see 2-3 kilograms (4.4-6.6 pounds) of milk increase, and so a loss of 7 kilograms (15.4 pounds) is huge!

Conclusion

Acidosis is a multifaceted problem that affects not only the physical health of livestock but also the economic viability of dairy farming. There is also the hidden cost of subacute ruminal acidosis (SARA). The connection between acidosis, leaky gut and the absorption of endotoxins highlights the intricate relationship between nutrition, gut health and animal immunology.

One of the biggest challenges of mitigating the potential losses of acidosis, a leaky gut and an inflammatory response, is seeing that the challenge is present. Without taking blood samples to monitor the inflammatory response, practically, it is difficult to see. At times of stress, there may also be a raised somatic cell count (SCC). However, there are many factors that can also cause a raised SCC.

The energetic cost of inflammation equal to 7 kilograms (15.4 pounds) of milk is significant – and nutritional approaches need to consider how to mitigate this. You wouldn’t inject a dose of E. coli into an animal daily, but that is effectively what you are doing if the rumen is not managed well.

Feeding to manage the rumen or to mitigate the impact of both endotoxins and mycotoxins should be a part of all nutritional strategies, particularly for high-producing dairy cows.

Indeed, if cattle are already under threat from an environmental endotoxin – and mycotoxins also happen to be present in the ration they are receiving – production losses can be magnified because of an additive challenge to optimal animal health.

For more information, please contact Bryan Miller, technical business manager at Volac Inc., at bryan.miller@volac.com. For more information about UltraSorb R, visit volac.com/feed-additives.