Balancing act: Finding the sweet spot in trace mineral supplementation

Trace minerals are essential to maintaining health and productivity in livestock animals. Traditionally, trace minerals were fed based on the minimum level required to overcome a deficiency symptom and not necessarily to promote productivity. Feeding adequate amounts and sources of trace minerals is essential to optimize production, health and feed costs and to minimize effects on the environment.

The growing uncertainties associated with trace mineral requirements and supply puts nutritionists in the dilemma of balancing the costs of either underfeeding or overfeeding trace minerals. A deficiency will impair health in dairy cows, leading to problems such as retained placenta and mastitis, and can decrease reproduction and lactation performance. On the other hand, excess supply will inflate feed costs and increase the risk of environmental pollution and toxicity, and it may also result in unwanted antagonistic interactions among minerals, leading to poor absorption.

Dietary trace minerals are supplied from feedstuffs and mineral supplements. The National Research Council (NRC) requirements are based on both sources of trace minerals, accounting for their absorption coefficients. Feed trace minerals usually have lower absorption coefficients compared with supplements. Furthermore, mineral supplements differ in their bioavailability. The NRC (2001) requirements appear to be adequate for most minerals, except for manganese and cobalt, for which new data suggests higher concentrations.

Inorganic minerals generally have lower bioavailability compared with organic minerals. Inorganic minerals become free in the rumen and can interact with other feed components. They can also bind to other minerals and pass through the gastrointestinal tract unabsorbed. Inorganic minerals may also include a source of contaminants, such as the heavy metals cadmium and lead. The presence of inorganic trace minerals in premix feeds can negatively affect the stability of enzymes and vitamins. To circumvent these bioavailability and absorption uncertainties, inorganic minerals are often supplemented at multiples of NRC requirements, which may further reduce their absorption and may reduce animal health and performance.

The Total Replacement Technology™ (TRT) mineral program at Alltech offers trace minerals (Bioplex®, Sel-Plex®) to provide highly available and traceable sources of minerals that support the animal’s requirements.

Most lactation diets will supply adequate to excessive amounts of iron, while other trace minerals will be supplied at amounts below NRC requirements, ranging from 40 percent to 85 percent. The TRT program should accommodate most situations but may need to be adjusted for specific situations in which extreme dietary concentrations are found. Regular assessment of trace mineral levels in forages is critical to building a more efficient mineral nutrition program.

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