Zinc is an essential mineral in dairy nutrition, playing a key role in growth, immune health, and reproductive performance. But not all zinc supplements are created equal. A recent study published in the Journal of Dairy Science sheds new light on how well different forms of zinc are absorbed by young calves — and it may help dairy producers make more informed choices when formulating rations.
What the Study Looked At:
Researchers compared two common zinc sources:
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Zinc sulfate (Zn-SO) – an inorganic form.
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Zinc methionine hydroxy analog chelate (Zn-MHAC) – an organic form.
To measure how much of each was actually absorbed, the team used stable isotopes — safe, non-radioactive markers that track zinc inside the body.
Eighteen young Holstein calves were given a single dose (0, 4, or 8 mg) of either zinc source. Over the next 72 hours, researchers measured how much zinc showed up in the blood and various tissues (like liver, skin, lungs, hoof, and bone).
Key Findings:
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Higher absorption from organic zinc: Calves given Zn-MHAC (organic) had significantly more zinc in nearly all tissues tested compared to those given Zn-SO (inorganic).
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Dose mattered: The 8 mg dose led to greater zinc uptake than 4 mg or 0 mg, regardless of the source.
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The liver was the only organ where weight changed based on dose (heavier with 4 mg), but this was not tied to the source type.
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Blood zinc measurements didn’t differ by source, showing the importance of tissue testing to detect long-term zinc uptake.
Why This Matters:
While blood tests are easy to collect, they may not tell the full story when it comes to zinc absorption. This study confirms that tissue zinc levels — and therefore potential health benefits — are more affected by the form of zinc used.
Takeaway for Dairy Producers:
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Organic zinc sources like Zn-MHAC may be more bioavailable, meaning the calf’s body can absorb and use them more effectively.
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Using stable isotopes offers a reliable way to measure mineral absorption without radiation risk.
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Choosing the right form and dose of zinc can support better health outcomes in youngstock.
Quick Summary for Decision-Makers:
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Organic zinc (Zn-MHAC) = better absorption
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Higher zinc dose = greater uptake
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Blood zinc alone may not reflect true absorption
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Stable isotope tracking = accurate, non-invasive method
This research supports considering organic trace minerals in calf diets, especially when aiming for optimal growth and immune function.
