Trace minerals: Model guides responsible use
Trouw Nutrition has developed a model to guide optimal mineral supplementation for zinc, manganese and copper. This easy to use ‘mineral check’ supports responsible use of trace minerals, delivering benefits for the cow, the farmer, and the environment.
Trace minerals such as zinc (Zn), manganese (Mn), copper (Cu), and iron (Fe) play a vital role in supporting long-term productivity in dairy cows. Their absorption is a regulated process: when dietary supply falls below requirements, absorption efficiency increases, while excessive intake reduces absorption. This has been demonstrated, for example, in studies on Zn by Weigand and Kirchgessner (1978). For Mn and Cu, higher dietary levels have also been directly linked to increased excretion.
Despite this regulatory capacity, imbalances can still create challenges. Under-supplementation may compromise animal health and performance, while over-supplementation can cause toxicity, increase feed costs, and result in greater excretion of unused minerals into manure and urine, with negative consequences for both the environment and farm economics.
Overfeeding trace minerals is (still) common
The NASEM 2021 guidelines define the minimum dietary levels (in ppm) required to maintain cows at an optimal mineral supply: 10 ppm for Cu, 66 ppm for Zn, and 37 ppm for Mn. Despite this, many nutritionists remain concerned about deficiencies, particularly Cu deficiency, and routinely supplement at levels well above these recommendations.
This practice is widespread across the globe as shown by research. Studies from 139 herds in California and Eastern Canada found that 90% of farms provided Cu levels exceeding the NASEM 2021 guideline of 10 ppm for a lactating cow producing 32 kg of milk. In the UK, a survey of liver Cu concentrations in 510 cull cows revealed a significant risk of chronic Cu toxicity. Similarly, in the Netherlands, 10% of liver samples exceeded 1,066 ppm.
Trace minerals in basal diet often forgotten
Over-supplementation often arises from concerns about deficiencies, but it also occurs when the trace minerals already present in the basal diet (forages and by-products) are overlooked. Taking the basal diet’s contribution into account, alongside maximum tolerance levels, helps producers and nutritionists prevent the toxicity, environmental impact, and economic losses linked to excessive supplementation.
Trace mineral levels in the basal diet can be determined through representative sample analyses. However, routine testing of feedstuffs for trace minerals is uncommon and not standard in NIR testing, making it is both costly and time-consuming. Moreover, precise values are not always necessary, since daily dry matter intake per cow varies and (as noted earlier) cows can regulate trace mineral absorption to a considerable extent.
Easy calculation of minimum supplementation
To make trace mineral information on basal diets easily accessible, without the need for on-farm testing, Trouw Nutrition has developed a practical and user-friendly calculation model. The tool draws on data from 5,000 tested diets, complemented by literature reviews and Trouw Nutrition R&D insights on individual feed ingredients. By combining the variation observed across these 5,000 diets (expressed in percentiles, see Table 1) with the NASEM 2021 guidelines, the model can estimate the expected trace mineral content of the basal diet and recommend the minimum supplementation levels needed to minimise the risk of underfeeding.
Model aims to create more awareness
The purpose of the model is not to prescribe exact supplementation levels for every production stage or farm. Rather, it aims to raise awareness that the trace mineral content of the basal diet should always be considered when determining supplementation to remain within the optimal total supply. The values generated by the model serve as a valuable starting point for discussions between farmers, nutritionists, and consultants on how supplementation can be fine-tuned.
For instance, if a dairy cow is currently receiving 25 ppm Cu, but the model, based on the basal diet calculation, suggests that 10 ppm would be sufficient, the level could be reduced by 15 ppm. If there is concern that the basal diet estimate might be slightly low, the reduction could be adjusted to 12 ppm instead of 15. Even then, the change would still significantly lower feed costs, improve animal performance, and reduce environmental excretion. Similar considerations can be applied to Zn and Mn, while in many cases the basal ration already provides adequate Fe.
Source of trace mineral matters
Taking the trace minerals already present in the basal diet into account and optimising supplementation is an important step toward responsible mineral use, bringing benefits for the cow, the farmer, and the environment. Yet, the story does not end there. The source of trace minerals is equally critical, as bioavailability varies widely between inorganic and organic forms. Even within organic sources, differences exist in their modes of action and uptake pathways.
Current NASEM guidelines for trace minerals are based on inorganic sources (sulphates). However, extensive research demonstrates that Selko IntelliBond hydroxy trace minerals offer superior bioavailability compared with sulphate-based sources. This advantage stems from their unique crystalline structure, which significantly enhances trace metal absorption across the intestinal wall into the bloodstream. Thus, combining the right supplementation level with a more effective mineral source can further improve animal health and overall outcomes.
Turning challenges into opportunities
Dairy producers worldwide face growing pressure from both regulators and consumers to adopt more sustainable practices, protect animal welfare, and achieve production targets without compromising profitability. Animal nutrition is central to this balance, and on many farms, there is considerable opportunity to reduce trace mineral supplementation. Overfeeding remains common, largely because the trace mineral content of the basal diet is often overlooked.
The new model from Trouw Nutrition calculates the trace mineral contribution of the basal diet and identifies the optimal supplementation level. This tool, freely available online as Trace Mineral Check, is part of Selko Responsible Trace Mineral Management. In addition, selecting more bioavailable trace mineral sources can further enhance outcomes, creating benefits for animals, farmers, and the environment alike.
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