When it comes to trace minerals in the dairy ration, not all forms of trace mineral supplementation are equal. As researchers learn more about the form and function of trace minerals, questions have arisen about whether the sulfate trace minerals in the dairy ration could cause more harm than good.
Pioneers in hydroxy trace mineral nutrition, Micronutrients recently invested in research exploring the complex interactions occurring in the dairy cow rumen environment. Findings from trials conducted in partnership with leading research universities suggest that the longstanding practice of including sulfate trace minerals in the dairy ration may significantly decrease fiber digestibility compared to non-sulfate sources of trace minerals.
Below, Dr. Scott Fry, Director of Technical Sales Support at Micronutrients, speaks about the research and why dairy managers and nutritionists may want to consider removing sulfate trace minerals from the dairy ration.
DB: Sulfate trace minerals have been used in the dairy ration for many decades, so what prompted a concern?
(Dr. Fry) Sulfate trace minerals are widely used as the source of trace minerals to provide supplemental zinc, copper and manganese to the cow. But the chemical attributes of sulfate trace minerals – specifically, their high solubility in water and reactive nature – raised questions about how sulfate trace minerals interact behave in the rumen. Weak ionic bonds and the water solubility of sulfate trace minerals could cause minerals to disassociate in the rumen. Free metal, such as copper and zinc, can form indigestible complexes with antagonists or harm rumen microbes.
We know that rumen microbes play a big role in energy and protein nutrition of the dairy cow by digesting fiber and other carbohydrates. As a research-driven organization, Micronutrients partnered with research universities to compare the performance of sulfate trace minerals and hydroxy trace minerals (our IntelliBond® product) in the rumen.
(Dr. Fry) Studies were conducted between 2014 and 2016 with animal nutrition scientists at The Ohio State University and Colorado State University. The studies looked at the effect of trace mineral source on total tract neutral detergent fiber (NDF) digestibility. Both studies compared sulfate trace minerals to hydroxy trace minerals (IntelliBond).
DB: What were the key findings of the research?
(Dr. Fry) Research findings focused on two primary concerns with sulfate trace minerals. First, the Colorado State University study confirmed that following ingestion, the weak bonds of sulfate trace minerals dissociate easily, releasing free metals into the cow’s rumen. Looking at copper and zinc, we saw sulfate trace minerals were significantly more soluble compared to hydroxy trace minerals.
The second concern relates to a top-of-mind predictor of productivity closely monitored by dairymen: NDF digestibility. The research found a decrease in NDF digestibility of 1.4 to 3.4 points when sulfate trace minerals were fed compared to hydroxy trace minerals (Figure 1). From an energy standpoint, the literature suggest that a one point increase in NDF digestibility translates to a half-pound increase in production of fat-corrected milk.
DB: What do producers think about these findings?
DB: What kinds of questions have you received regarding these findings?
(Dr. Fry) Two questions commonly come up in conversations with dairymen. The first relates to why sulfate trace minerals have been used in the ration for so long, considering the harm they can cause. It’s true; sulfate minerals have been used for a long time. However, only recently have we learned about the harm sulfate trace minerals cause in the rumen. The second question relates to a mindset that it’s necessary to feed trace minerals to the good microbes in the rumen. Yet when you look at the amount of rumen soluble trace minerals from forages and feedstuffs, it covers the trace mineral requirement of microbes in the rumen.
DB: What trace mineral options are available to producers who want to stop using sulfate trace minerals in their rations?
(Dr. Fry) There are three paths forward when removing sulfate trace minerals from the dairy ration. One option is to feed all organic trace minerals; however, the benefits may not be offset by the additional cost. A second option is to replace sulfate trace minerals with hydroxy trace minerals. And a final option is to replace sulfate trace minerals with a ratio of organic and hydroxy trace minerals.
DB: Is Micronutrients conducting additional research?
(Dr. Fry) Yes; we’re excited about a series of experiments under different conditions where we really hone in on the activity that’s taking place in the rumen as it relates to solubility and nutrient digestibility. The rumen is a very complex environment with a lot of things going on. The unique chemical makeup of hydroxy trace minerals plays a big role in the mode of action. Micronutrients continues to invest in understanding how this chemistry supports the animal.
(Above) In two studies, cattle receiving sulfate trace minerals in their feed showed a decrease in fiber digestibility of 1.4 to 3.4 points, compared to cattle receiving non-sulfate sources of trace minerals.