High-producing dairy cows are more susceptible to negative impact from stressors in their feed and in their environment. But what matters for performance and efficiency is how the cows respond. Feeding the right natural bioactive substances can help the animal adapt its response in a way that helps maintain milk quality and component yields. This article focuses on how to adapt to the mycotoxin deoxynivalenol (DON) for profitability.
Stress reactions in response to DON
Typical stress reactions on the cellular level in response to DON in the dairy cow include oxidative stress, inflammatory responses, as well as hormonal changes that affect feed intake. Symptoms seen as a result are related to increased somatic cell counts and reductions in feed intake, milk production and milk component yields.
On top of that, DON is known to have a negative impact on the rumen microflora, which again has been shown to have a negative impact on milk component yields, particularly milk protein.
Why high-producing cows are more at risk
Ruminants are regarded as quite resistant to DON because of the detoxifying potential of rumen microbes. However, the detoxification capacity of rumen microbes depends on the feed passage rate and rumen pH.
Feed passage rate is generally higher in high-producing dairy cows because of higher feed intakes. This will affect the time available for rumen microbes to degrade DON into a nontoxic form.
Rumen pH levels can be low due to the increased amount of concentrate eaten, which again will affect the composition of the rumen microflora. Jeong et al. (2010) report that high concentrate-to-forage ratios reduce the amount of DON detoxified by rumen bacteria by 14 percent.
The liver needs extra care
A high-energy demand and an increased oxygen requirement in high-producing dairy cows augment the production of reactive oxygen species (ROS). When ROS are produced faster than they can be neutralized by the cow’s own antioxidative defense, oxidative stress results. Research has confirmed that oxidative stress is greater in early lactation than in pregnancy.
Since the liver has a high metabolic activity, it is more susceptible to damage from oxidative stress. A negative energy balance initiates lipid mobilization, which leads to high concentrations of non-esterified fatty acids (NEFAs).
Shi et al. (2016) reported that metabolism of large amounts of NEFAs to ketone bodies induces oxidative stress in the liver of dairy cows. This can then aggravate the development of fatty liver by inhibiting the production of very low-density lipoprotein (VLDL). DON, which is known to increase oxidative stress and reduce feed intake, can exacerbate this further.
Liver function can be severely impaired by fatty infiltration, which is associated with decreased milk production, reduced fertility and health problems, such as mastitis and ketosis.
Oxidative stress in the liver is also known to cause inflammatory damage of the liver, which further impairs the metabolic function of liver cells and promotes the development of ketosis. McArt et al. (2015) from Cornell University estimated the total cost per case of ketosis to be $289, demonstrating the importance of extra protection of the liver from stressors such as mycotoxins.
Adapt to disarm DON
The response to DON at the cellular level and in the rumen of the dairy cow will determine the impact DON has on milk profits. Supporting the animal’s own defense mechanisms to reduce the negative stress reactions caused by DON reduces the impact DON can have on performance, health and milk quality in the dairy cow.
Since plants have evolved to withstand stressors, some plant extracts have proven beneficial to counter the same reactions that cattle have to stress on the cellular level. As a means of defense, plants can have components with high antioxidative capacity and anti-inflammatory activities. On top of that, certain plant extracts have demonstrated a positive impact on appetite regulation and rumen efficiency when applied to animal feed.
Consequently, feeding the right combination of plant extracts can be a strategy to adapt the response to DON in the dairy cow to help maintain profitability in the face of a challenge.
For instance, plant components with a high antioxidative capacity can help to increase the level of antioxidative enzymes and antioxidants to support the cow’s own antioxidative defense in the liver. Feeding those types of components can give the liver a better chance of fighting ROS produced by mycotoxins in the liver and, thus, minimize the negative consequences from oxidative stress on liver function and cow performance. 
References omitted but are available upon request. Click here to email an editor.
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Gwendolyn Jones
- Anco Animal Nutrition Competence
- Archer Daniels Midland Co.
PHOTO: Photo by Jenna Hurty-Person.
