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In the past, we balanced micronutrients using the “holiday pie theory” – if some is good, more is better. 

But that isn’t the case anymore.  In fact, overfeeding micronutrients can not only be costly to the producer, but it can also be deadly to the animal.

Find a good balance

Overfeeding trace nutrients, like copper (Cu), zinc (Zn) and manganese (Mn), can be costly and wasteful.  Biologically, when you overfeed these trace nutrients, the dairy cow’s system recognizes the excess and removes it from the system.  Essentially, the farmer pays extra for these micronutrients to ultimately end up on a field in the form of manure.

While Zn and Mn can be financially costly, they don’t bare the costs associated with Cu's toxicity.  Cu is stored in the liver, which is a good thing when dietary Cu is lacking or it is needed for an immune response.  However, when liver Cu stores are in excess, the mobilization of liver Cu can be lethal.

Underfeeding these trace nutrients can also be costly and dangerous.  Cu, Zn, and Mn play a vital role in cellular function and animal survival. 

To complicate things further, we don’t have an absolute method of measuring these trace nutrient levels, and other “antagonists,” such as sulfur (S) and iron (Fe), can limit the amount of absorption of these micronutrients.

For these reasons, feeding some excess is warranted, but you must be aware of not only the financial costs, but also the potential costs of reduced animal health.

Trace nutrient source matters

Research has demonstrated feeding specialty or organic forms of Cu, Zn, and Mn holds several benefits over sulfate-sourced minerals.  Some of these advantages include increased stability in the rumen, lower chance of absorption being hindered by other nutrients, increased fiber digestion, and increased nutrient absorption in forage-based diets.

Feeding organic mineral sources can also improve hoof health.  It has been the long-running theory that trace nutrients, such as iodine (I), biotin and Zn, aid in immunity and keratinization of the tissues within the hoof.  New research from The Ohio State University observed feeding Zn glycinate from an organic source with Cu and Mn sulfates reduced the amount of Treponema bacteria in manure.  Treponema are spiral-like bacteria that target the soft tissues of the hoof and have been associated with digital dermatitis.

In theory, reducing the amount of these bacteria in manure that is well trafficked by cow hooves daily should improve hoof health.  However, the exact cause of this decrease, or why the combination of the mineral sources reduces the bacterial excretion, is not known.

Another research study, completed at the University of Illinois, observed a reduced incidence of heel erosion when lactating dairy cows were fed Cu, Zn and Mn from amino-acid complexed minerals and cobalt glucoheptonate compared to sulfate sources.

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Practical application

The days of formulating trace minerals based on the “holiday pie theory” should be a thing of the past.  While trace minerals play a significant role in rumen function and digestion, it is important to feed the appropriate amounts to avoid extra out-of-pocket expenses and adverse health effects in the animals.  Feeding more stable specialty or organic minerals versus sulfates can also improve health and performance.

This article originally appeared in the Jan. 10, 2018 issue of Hoard’s Dairyman. 

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