Findings from studies conducted by leading research universities and pioneers in trace mineral nutrition of dairy cattle suggest it may be time to rethink the use of inorganic trace minerals in the dairy ration. Dr. Scott Fry from Micronutrients presents an overview of recent research suggesting that the source of trace minerals in a dairy ration can have a big impact on health and performance of dairy cattle.

Hydroxy trace minerals offer better mixing and handling qualities along with equal or better performance compared to higher-quality organic trace minerals. Research was conducted to compare how different sources of trace minerals work inside the cow’s gastrointestinal tract, resulting in a number of important findings.

Once broken down in the rumen, the zinc and copper ions originally linked within the sulphate trace mineral now possess antimicrobial properties and can harm beneficial bacteria that digest fibre. In contrast, hydroxy trace minerals have a crystalline structure and covalent bonds that make them significantly less soluble. As a result, disassociation in the rumen is minimal, thus making it all but impossible for free metal ions to be released in the rumen environment.

‘Good’ microbes in the rumen play an essential role in promoting fibre digestibility. They support the production of important volatile fatty acids used by the dairy cow for optimised productivity and well-being. As these microbes multiply and travel down the digestive tract, they become a high-quality source of by-pass protein for the dairy cow, providing about half the total dietary protein needed for milk production. Thus, a trace mineral source that interferes with microbial activity in the rumen – where 90% of digestion takes place – can interfere with the performance and health of dairy cows.

A practical observation is that sulphate trace minerals have, for many decades been used in footbaths for dairy cows for their efficacy in killing microbes. Unfortunately, the same properties that make sulphate trace minerals effective in footbaths can potentially harm rumen microbial populations.

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