Achieving essential trace mineral formulation requirements via NASEM Dairy 2021 Requirements for dairy cows

Consistently optimizing the correct formulation of essential trace minerals within dairy rations is essential to maximize cow productivity and well-being, while protecting the environment. This process is now referred to as “Precision Trace Mineral Nutrition”, which requires that dairy cattle be supplied with both the correct amount and source of individual trace minerals to support optimized animal performance and health.

Dairy cow performance has increased over the last two decades. Producers and their nutritionists have elected to arbitrarily increase trace mineral supplementation levels to higher and higher levels with the general belief that more, must be better! While on the surface this strategy may sound logical, ongoing research continues to indicate that overfeeding of trace minerals has little to no benefit in dairy cattle. And may in fact have a negative impact on cow health using the example of increasing numbers of sudden deaths resulting from copper toxicity. Over feeding trace minerals can also have a negative impact on rumen function, the absorption of other essential nutrients in the ration and environmental compliance.

To initiate a Precision Trace Mineral Nutrition program requires a few basic steps that have been well developed and communicated within the most recent NASEM Dairy 2021 requirements manual (formerly referred to as NRC Nutrient Requirements of Dairy Cattle). The new NASEM Dairy manual calculates the dairy animal’s total trace mineral requirements based on a factorial evaluation of maintenance, growth, reproductive and production requirements of individual animals. This calculated requirement is the total amount of an individual trace metal required to meet the needs of the animal at a selected stage of age and production.

The NASEM Dairy 2021 Requirements replace the NRC Nutrient Requirements of Dairy Cattle and contain dairy cattle requirements based on the results of numerous independent studies. This has resulted in an increase in the total amount of both zinc and manganese required, but a slight decrease in the amount of copper required per animal per day based on adequate dry matter intakes. Please note that these published trace metal requirements are calculated to meet the cow’s requirement under normal production conditions. Conditions are not always normal due to environmental, production or metabolic challenges. Recent publications authored by several respected dairy nutrition professionals have indicated a potential benefit of further increasing certain trace metal requirements by 10 to 20%. This action is designed to offset any additional physiological and environmental demands the herd may encounter.

To meet dairy cow requirements, formulators must calculate the total supply of available trace metals that are available to the dairy animal. Most importantly, this includes an understanding of the level of essential trace metals that are present within the basal ration ingredients. While some nutritionists may completely disregard this contribution, it is clear the cow cannot escape the influx of trace metals present in basal ration ingredients! Disregarding basal ingredient contributions and supplementing the trace metal requirement of all required trace metals will result in the over supplementation of dairy animals.

Precision Nutrition requires that nutritionists understand the cumulative levels of essential trace metals present within the basal ingredients of the ration and the amount of ration consumed per animal per day. Once understood, the total basal trace metal amount can be subtracted from the animal’s trace mineral requirement to arrive at the amount of trace metal that must be supplied via a commercial trace mineral source to meet the animal’s total trace metal requirement.

When considering the source of supplemental trace mineral supplementation, the NASEM Dairy 2021 Requirements uses sulfate trace minerals as its default sources. Certain organic trace minerals have been vetted by independent research to have a higher level of bioavailability. Thus, if the nutritionist’s decision is to use an improved source of trace mineral supplementation, i.e. hydroxy trace minerals, the level of supplemented trace minerals should be reduced to reflect the increased level of bioavailability of the improved source. As an example, if an additional 500 mg of zinc is required in addition to the level of zinc present within the basal ingredients, and the nutritionist replaces sulfates with a hydroxy zinc trace mineral source, the amount of zinc supplied from the hydroxy source could be lowered by 100 mg per cow per day to reflect the average increase in the relative bioavailable of the hydroxy zinc source compared with the sulfate source. Given the high solubility and reactivity of the sulfate source compared with the hydroxy source, several additional benefits can be realized. This includes maintaining optimized rumen fibre digestibility, significant reductions in the tie up of other essential nutrients in the ration and improved palatability.

To summarize, it is important to note that the trace mineral source is of critical importance to the well-being and productivity of the dairy animal. It is even more important to ensure that dairy rations are being correctly formulated to provide the correct trace mineral requirements, based on the most recent research and laboratory analytical reports. The best trace mineral source, when formulated incorrectly can be as much of a problem as it can be a benefit to the animal. To avoid this mistake, it is critical that you:

• Have a good understanding of the trace metal content of the feeds you are feeding based on wet chemistry lab results, or tabular values included within the new NASEM Dairy 2021 Requirements manual.
• Use herd records to fully understand what level of dry matter intake can be expected within different productions groups across the full year.
• Calculate the animals’ requirement using the new NASEM Dairy 2021 Requirements manual based on the animals’ age, weight, stage of production and reproductive status
• Understand the impact of any additional stressors that may be present (e.g. higher Mo and sulfur levels in the feed and water) to arrive at the correct, total trace metal requirement.
• Subtract the basal trace metal level from the total trace metal requirement to identify the amount of supplemental trace minerals required to meet the total trace metal requirement of the dairy animal.
• Carefully consider the selection of the trace mineral source that will allow for a higher level of Precision feeding based on the trace mineral source’s ability to provide higher levels of bioavailability, productivity, and well-being.