While trace minerals such as copper, cobalt, manganese, selenium and zinc have low inclusion rates in the rations of a dairy cow, they perform critical functions for the animal, including bone development, energy and protein metabolism, antioxidative protection, reproduction, immune function, nerve signaling and muscle contraction. Trace minerals are found in forages and other ingredients, but their availabilities are variable; therefore, all or part of the trace minerals required by the animal are commonly provided as supplements in the ration.
Inorganic trace minerals are mined from the ground and can be seen on feed tags as oxides and sulfates. They tend to be reactive with the environment and can interact with other feed ingredients to prevent absorption. Organic trace minerals, on the other hand, are trace minerals complexed with organic (carbon-based) molecules, ranging from single amino-acid mineral chelates to complex mineral proteinates. Organic trace minerals, especially proteinates, are similar in form to the trace minerals found in plants. This allows for better absorption and utilization by the animal compared to inorganic forms, resulting in more efficient use of trace minerals as well as better function.
In addition to better absorption and use by the animal, organic minerals are more stable in the feed due to the molecular cushioning afforded by chelation. Studies have found that the trace mineral source can impact the stability of other ingredients when stored over time in the same concentrate mix. For example, researchers found that a concentrate mix containing inorganic minerals stored for 20 days showed a 20% reduction in vitamin E stability, while a concentrate mix containing trace mineral proteinates did not reduce vitamin E stability.
Similar work has found that inorganic minerals reduce the activity of enzymes when stored in the same concentrate mix. It is important to understand how the trace mineral source may impact the activity of other – often expensive – ingredients when stored in the same concentration mix.
Trace mineral form can also influence production potential. For the most part, a cow’s requirements for minerals are dictated by its age, production stage and level of production. The National Research Council (NRC) Nutrient Requirements of Dairy Cattle guidelines contains mineral recommendations for all life stages of dairy cattle based on the available research, much of which is decades old and uses only inorganic mineral sources. There is some evidence for poultry and swine, as well as dairy cattle, that the trace mineral source can impact how much mineral the animal requires and its performance.
A recent study compared mineral supplements for lactating cows containing 100% of the NRC recommendations as inorganic trace minerals (sulfates and oxides), 70% of the NRC recommendations as inorganic and 70% of the NRC recommendations as organic trace minerals (proteinates). Milk production was similar for the 100% NRC inorganic and 70% NRC organic groups, indicating that cows required less of the mineral to support the same amount of milk when fed the proteinate form. Further, the 70% NRC inorganic treatment resulted in less milk than the 100% NRC inorganic and 70% NRC organic treatments, indicating that the animal’s requirement for minerals was not met with the lower inclusion of inorganic sources.
Trace mineral source has been found to affect performance and immune function in dairy and beef cattle. Several studies have illustrated an improved milk production when lactating cows are fed organic proteinate trace minerals compared to inorganic sources, averaging 5-7 pounds of milk per day. This impact on performance may be due to several factors, such as improved bioavailability of the mineral, reduced antagonism with other minerals and compounds in the feed, and improved underlying immune function.
Inorganic minerals can be antimicrobial. Think about feeding the same copper sulfate used in a footbath to a dairy cow. This antimicrobial effect is important because the rumen is full of bacteria and protozoa critical for digestion in the cow. Studies have shown that inorganic minerals depress rumen fermentation, leading to reduced feed digestion and energy availability for the cow.
Organic proteinates do not affect rumen function, and studies have shown that organic trace minerals lead to improved immune function; for instance, cows experience a reduced somatic cell count and incidences of mastitis, as well as faster recovery from clinical mastitis. Feedlot studies have shown reduced mortalities overall, specifically from respiratory issues, when steers were fed organic minerals.
Studies in dairy and beef cattle have examined the impact of trace mineral source fed to the gestating cow on the early life health, growth and performance of their offspring. Researchers found that heifers from cows that received organic minerals during the dry period were healthier during the preweaning period (zero to eight weeks) as indicated by improved overall health score and reduced biomarkers for disease.
In beef cattle, calves born to cows who consumed organic trace minerals had higher total immunoglobulins at one day old, indicating better health during early life. Calf health and growth during the first eight weeks of life have been shown to correlate with milk production through the first lactation. Calves that experience no or limited sick days produce more milk in the first lactation than calves that get sick.
Heifers from cows that received organic minerals during the dry period reached puberty faster and calved about one month earlier than heifers from cows that received inorganic trace minerals during the dry period. Similar results were found in beef cattle, where offspring from organic mineral-fed cows attained puberty and were confirmed pregnant earlier than offspring from inorganic mineral-fed cows.
The impact of trace mineral source on fertility and reproduction may be attributed to improved bioavailability and the intestinal absorption of organic trace minerals, compared to inorganics. This data indicates that the trace mineral source provided during late gestation can impact the early-life health and fertility of the mature cow.
One of the main determining factors for a farmer considering adopting a new technology is price. Organic trace minerals cost more than inorganics; however, the question should not be, “How much will it cost me to use organic trace minerals at my dairy?” Rather, the questions should be, “What are inorganic trace minerals costing me in reduced rumen fermentation, degradation of vitamin E, reduced performance, immune function and fertility?” and “What can I gain if I feed organic minerals?” 
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Amanda Gehman
- Research project manager
- Alltech
- Email Amanda Gehman
