Cows are more resilient to the impact of mycotoxins such as DON, because the rumen microflora can degrade DON to a non-toxic form. However, there are certain situations where even cows can become quite vulnerable to the effects of mycotoxins. It is important to know which ones they are and what you can do to have more control over the response in cows.
How do cows respond to the DON mycotoxin?
The first line of defense to DON is the rumen microflora. Rumen microbes effectively transform DON into non-toxic metabolites.
However, the detoxification capacity for DON by rumen bacteria can be compromised in high producing dairy cows, which are fed greater amounts of concentrates and where feed passage rate is high. Both conditions will affect rumen pH and the time available for rumen microbes to degrade DON into non-toxic metabolites.
DON that is not transformed into its non-toxic metabolites will increase the production of reactive oxygen species (ROS) at the cellular level, lead to oxidative stress, which eventually can also increase inflammatory responses in the cow. This again can affect milk quality and milk yields as well as the cows health. It has been demonstrated that dairy cows fed diets contaminated with DON, produce lower milk yields, decreased milk fat and have increased milk somatic cell counts. Furthermore they are also more likely to experience metabolic disorders in the transition period.
Factors that can exacerbate a negative response to DON
Other stressors can exacerbate the impact DON in diets can have on cows, as they will cause the same kind of stress reactions on the cellular level. In combination the effects on milk production and health will then likely be higher. These stressors include:
- Transition period status
- High milk yields
- High concentrate diets
- High ambient temperatures/ summer heat
Building resilience to mycotoxins in dairy cows
The above learnings highlight, that helping cows to better deal with stressors such as high productivity, transition period, high ambient temperatures and high concentrate diets, will ultimately reduce the vulnerability to the effects from mycotoxins such as DON.
Therefore, feeding for an optimum rumen pH and rumen microflora is the first step to a higher resilience to DON in dairy cows. Good management practices that help cows ease through the transition period and keep them cool during hot summer months, will further reduce the vulnerability of cows to the potential impact of DON on health and performance.
Nutritional support to disarm mycotoxins
Traditionally, feed additives have been developed to attack mycotoxins in the animal’s digestive tract directly to counteract harmful effects from mycotoxins in the animal. However, both mycotoxin binders and mycotoxin deactivators have their limitations. It is well known that adsorption is not an effective strategy for most mycotoxins. Only certain bentonites work well with aflatoxins and some yeast cell wall components have been proven to bind zearalenone, based on specific structural fits. For other types of mycotoxins, particularly DON, binding strategies do not work effectively.
A more cost-effective strategy to counteract mycotoxins focuses on disarming mycotoxins by supporting the animal’s resistance to the harmful effects of mycotoxins. This strategy empowers animals to respond more efficiently to DON by reducing the extent of the stress reactions generally seen in response to them. For example, adding plant extracts to the diet that are known to upregulate adaptive mechanisms for the antioxidative defense of the animal and downregulate inflammatory responses, as well as maintain efficient rumen fermentation can support a more favourable response to nutritional challenges such as mycotoxins.