Both the level of individual trace minerals that are being formulated into the ration and their form are essential to achieving this objective. Feeding too much, or too little of an essential trace mineral can have a negative impact on cow well-being and productivity (see figure 1). Given that inorganic trace minerals are relatively cheap, overfeeding is relatively common in dairy cows, potentially leading to longer term health and longevity issues.

Twenty years of independent university research has shown that improved sources of trace minerals such as proteinates, complexes and chelates, and now hydroxy trace minerals can have a positive impact on achieving an optimized level of cow productivity and health while minimizing any negative impact on the environment (see figure 2).

The source of trace minerals that are being utilized to meet the cow’s trace metal requirement can have a major impact on bioavailability but also on the risk of undesired effects. Hydroxy forms of trace minerals are insoluble at a pH of 4 or higher. Rumen pH should be between 6 and 6.5, so hydroxy trace mineral crystals are essentially insoluble within the rumen, thereby maintaining optimal rumen function. In the abomasum, where the pH is between 2 and 3, the crystals dissociate layer by layer, resulting in a gradual and sustained release of trace metal ions into the duodenum. As a result, bio-availability of hydroxy trace minerals is high, but peak concentrations in the digesta always remain low.

In contrast, sulfate salts are highly soluble at neutral pH, resulting in high peak concentrations of free metal ions in the rumen. This has a number of negative effects:

• High levels of free ions have an antimicrobial effect in the rumen, which can result in poor fiber digestion102
• Free metal ions are able to bind with antagonists to form insoluble complexes, resulting in lost nutritional value and poor bioavailability

By feeding the correct source and level of trace minerals, one can avoid negative impact on:

• Stability of essential nutrients contained within the feed
• Rumen function, cow physiology, reproduction, and longevity because of:
  • Maintaining an optimized level of fibre digestibility in the rumen is essential to achieving increased dry mater intake, maximum forage efficiency and rumen health
  • Improved utilization of essential ration ingredients by the cow. Get more out of your rations, by minimizing the tie up of essential nutrients with highly reactive, free metal ions that are stealing nutrient value from your rations
• Environmental compliance

A first step is to always determine the correct level of trace metal that is required above the trace metal levels that are present in basal ration ingredients to meet the cow’s total requirement. Subsequently, the correct level and source of trace mineral can be selected. This will ensure dairy cattle are receiving a consistent level of essential trace metals needed to support optimized well-being and productivity. When considering what source of trace mineral should be selected there are five targets.

Reactive trace mineral forms such as sulfates can have a significant negative impact on stability and bioavailability of other essential nutrients (vitamins, fats, probiotics, prebiotics, amino acids) contained within the supplement. Sulfate trace minerals are commonly referred to as pro-oxidants, which simply means they will react with other unstable molecules present within the feed. Copper and/or zinc can quickly accelerate oxidation of unprotected fat sources in the feed, negatively impacting the value of the fat as well as several fat-soluble vitamins. If the feed is being pelleted, the moisture present within the pelleting process can ionize the metals allowing them to function as antimicrobial agents against expensive probiotics that may have been added to the feed. Hydroxy trace mineral sources do not have any of these negative effect on the availability of essential nutrients present in the feed.

Sulfate trace minerals are highly soluble in the rumen, resulting in high levels of reactive metals negatively impacting rumen function. While these characteristics may be of value when copper and or zinc sulfate are used in a foot bath, they quickly become problematic when used to deliver essential trace metals to the dairy animal. Reactive sources of trace minerals have a negative impact on rumen microflora, significantly reducing NDF digestibility in the rumen. An independent study105 showed that replacing sulfate trace minerals entirely with hydroxy trace minerals eliminated this negative response, resulting in an average 3-point improvement in NDF digestibility. A recent quantitative summary102 evaluating 11 independent comparisons found that feeding copper and zinc sulfate had a statistically significant, negative impact on NDF digestibility in lactating dairy cattle, resulting in a 1.7-points decline of NDF digestibility. University research has shown that each one point difference in NDFd can represent 0.25 to 0.3 kgs of daily milk production103.

More recent work[106] shows that the higher bioavailability of zinc resulting from feeding the hydroxy form has a positive effect the immune system and gut wall tissue integrity. This improves gut barrier function, reducing the risk of “leaky gut” and systemic inflammation in dairy cows during periods of stress.

Highly soluble trace minerals such as sulfates can significantly reduce the amount of trace metal and other essential nutrients that are available for absorption in the intestinal tract. When sulfate trace minerals encounter moisture, they quickly breakdown releasing their metal ions within the rumen. This allows the ion to form an unavailable complex with many essential nutrients such as phytates, other trace and macro minerals, oxalates, amino acids, forming new complexes that are no longer of any value to the dairy animal.
Hydroxy trace minerals essentially by-pass these negative effects in the rumen. This results in more biologically available trace metal arriving in the intestinal tract for absorption, while not affecting the availability of other essential nutrients in the ration.

Any trace mineral which is fed and not absorbed by the animal will end up in the environment. This result is not limited to trace minerals being fed, but also the essential nutrients and additives the trace metal ion has bonded with, such as phosphorus, phytates, mycotoxin binders, etc. Hydroxy trace mineral sources can significantly reduce the amount of metal complexes that are expelled into the environment by improving the absorption of essential metals and other essential nutrients from the ration.