Oxidative Stress in Dairy Cows

Oxidative Stress in Dairy Animals

It’s hard to attend a dairy meeting these days without hearing the term “oxidative stress”

at least once.

But very few people, nutritionists included, have a full understanding of the term.

What is Oxidative Stress?

In the cow’s body there is a natural balance between the formation of free radicals during the normal

metabolism of the cells and the internal antioxidant capacity of the animal that would prevent free radicals

from accumulating and harming the cells. Free radicals are atoms, molecule, or ions with

unpaired electrons. Free radicals may have positive, negative, or zero charge. These unpaired electrons

cause radicals to be highly chemically reactive.

What is Oxidative Stress?

What is Oxidative Stress?

In situations where the levels of free radicals exceed the antioxidant capacity of the animal, oxidative stress

occurs. High-producing dairy cows are prone to oxidative stress, and the situation can be exacerbated under certain environmental, physiological and dietary

conditions. Free radicals can damage the cells by oxidizing the

essential fatty acids of the lipid membranes, protein and DNA structure. This will impair production and

compromise health status of the animal.

What is Oxidative Stress?

Dietary lipids such as supplemental fat, oil seeds and distiller grains if not stabilized can be significant

contributors to the load of free radicals in the animalin addition to their negative effect on rumen microbial

growth.

Once critical structural damage occurs, antioxidants may no longer be able to repair the problems.

Therefore, it is crucial that dairy producers understand the need for proper balance and the role that nutrition

plays.

What is Oxidative Stress?

What is Oxidative Stress?

A cow with a large amount of oxidation occurring will have more tissue damage and it will have an increased

cost of maintenance.

This cow will be spending a larger proportion of its energy fixing and repairing processes and tissues,

rather than producing and reproducing.

Oxidative Stress in Dairy Animals

Dietary antioxidants (by protecting dietary lipids from being oxidized in the final feed and digesta) can

reduce the damage of free radicals to rumen microorganisms, the feed and digesta and

therefore reduce the damage of free radicals to rumen microorganisms and the animal.

Oxidative Stress in Dairy Animals

In dairy cattle, commercially available dietary antioxidants have been shown to improve fiber

digestibility in the rumen as well as milk yield, fat and the antioxidant status of the cows.

The antioxidant defense mechanism of the animal is also dependent on other dietary nutrients. Dietary

deficiencies in Se, Cu, Zn, Mn and vitamin E contribute to oxidative stress by compromising the endogenous

antioxidant enzymes and the immune response of the animal.

Oxidative Stress in Dairy Animals

Feeding adequate (but not toxic) levels of trace minerals has been shown to benefit the health status of

the cattle by improving the immune response and antioxidant status, leading to better animal

performance.

However, not all trace minerals sources are equally available. Under dietary antagonisms, organic trace

mineral have been shown to have higher bioavailability than the inorganic forms.

Oxidative Stress in Dairy Animals

Causes and Signs of Oxidative Stress

There are many causes of oxidative stress:Metabolic stress (milk fever, ketosis etc.)Disease challenges (both bacterial and viral)Early 1st lactation, low or high body condition score can also elevate oxidative stress. Environmental conditions such as heat stress and social stress increases oxidative stress. Vitamin and mineral imbalances can be linked to oxidative stress as well.Mycotoxins loads are among the most important feed-born factors contributing to oxidative stress and lipid peroxidation.

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Causes and Signs of Oxidative Stress

Clinical signs can include:Lower dry matter intake and milk production

Retained placenta and other metabolic issuesUdder edema MastitisDelayed first estrusDelayed first breeding Repeat breeding resulting from failure to conceive or from early embryonic death.

Nutrition and Oxidative Stress in Dairy Animals

Nutrition plays an important role in oxidative balance. Specific ingredients provide protection against

pathogen invasion or exposure. Certain nutrients also play a role in oxidative balance by increasing tissue integrity, strengthening the barrier to free-radical

attack.

A dairy cow’s nutrition program can help maintain oxidative balance. The nutrition program can benefit

from the proper balance of antioxidants, minerals and amino acids

Nutrition and Oxidative Stress in Dairy Animals

Talk to your nutritionist about:Commercially available antioxidant products which may fit into your herds program. This is particularly pertinent if you are feeding fat in your TMR.Make sure that the Vitamin E in your cows’ programs reflect current recommended standards. I balance for 1000 KIU/head/day in the milking herd and 2000-4000 KIU in the dry herd.Ensure that trace mineral nutrition in your herd is adequately addressed; I prefer chelated minerals.

Nutrition and Oxidative Stress in Dairy Animals

Ensure amino acids are balanced in all of your herd’s programs. This is particularly true for methionine. Methionine can also be converted to the amino acid cysteine, which is used extensively by the immune system.

Nutrition and Oxidative Stress in Dairy Animals

At the barn level: Watch vitamins, mineral, amino acids in your herds’ nutrition. Reduce metabolic diseases in your herd with a

comprehensive dry cow program. Vaccinate regularly Control heat stress Lower social stresses as much as possible with grouping

strategies. Mycotoxins have no place in dairy nutrition, manage them

accordingly. Body condition score regularly.