Results show beef cattle can tolerate up to 3,000 milligrams of added sulfates per litre of water — higher than expected
Researchers are surprised that beef cattle can tolerate higher concentrations of sulfates in their drinking water than previously believed.
A recent study at the Livestock and Forage Centre of Excellence at the University of Saskatchewan tested differences in feed intake, growth or feed efficiency, and mineral concentrations in the blood of beef cattle related to the level of sulfates in their drinking water.
When the sulfates in drinking water are too high, they bind with trace minerals in the rumen, making those minerals unavailable for the animal’s body to absorb.
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“There was an expectation that the recommendations were not as conservative as they are. We had anticipated that when we went above the Saskatchewan recommendations, we would see a reduction in intake or growth”, said Greg Penner from the U of S Department of Animal and Poultry Science.
National and provincial recommendations for suitable levels of sulfates in drinking water range from 1,000 to 2,500 milligrams of sulfates per litre of water, which varies widely in terms of what cattle can tolerate for water sulfate.
“From that perspective it was a bit surprising. However, when you look at the requirements or recommendations from the national research council, we’re right on the edge of what the upper limit would be. So perhaps it’s not that surprising that we saw some very subtle effects in mineral concentrations, but no effects from a growth or feed or water intake perspective,” he said.
Penner said the national and provincial recommendations were not science-based, which led to the research.
Saskatchewan has ample available water for cattle to drink, but much of it is of low quality with high concentrations of minerals.
But cattle producers often rely on the water in provincial pastures, which frequently exceeds the recommendations.
The 1.5-year program was the first major study initiated and completed in the specialized metabolism barn at the university’s Livestock and Forage Centre of Excellence, located south of Clavet, Sask., which opened in 2018.
Sixteen heifers were housed in individual stalls with separate water bowls. One group of four was a control group that received water with no sulfates.
The other groups of four received water with 1,000, 2,000 and 3,000 milligrams of added sulfates per litre of water, which was designed to mimic realistic levels experienced by some cattle in the real world.
Regardless of these levels of added sulfates, the cattle continued to drink and eat, resulting in normal weight gain.
Results show beef cattle can tolerate up to 3,000 mg of added sulfates per litre of water.
“The short story from the results side is we really didn’t see much for feed intake responses or water intake responses. No growth effects. We did see a reduction in copper concentrations in blood,” he said.
However, the level of copper is significant, having been linked to the likelihood of cattle becoming and staying pregnant.
“Reductions in serum copper tell us, while everything looks good from an intake and growth perspective, there may be some concerns related to reproduction,” he said.
He said a producer might not see anything in terms of growth rate, feed and water intake, but those negative impacts may be hiding deeper and may be affecting trace mineral status, which could affect fertility.
The study also verified that cattle fed high forage diets are more tolerant of high-water sulfate concentrations than cattle fed more grain.
While the new study challenges wide-ranging old information, Penner said to be careful of general recommendations, which are averages.
He said it’s also important to consider that the cattle used in the study spent all their time in the research barn and were not exposed to normal ambient conditions.
“If we did the work during the middle of summer when we have a heat wave, we may see some different effects because that should cause those cattle to drink more water. And if they did drink more water, they would be exposed to more sulfate,” he said.
He said producers should consider water quality and water access for their animals and ensure the water is safe to drink. This involves testing to monitor dissolved mineral concentrations to ensure guidelines are met.
This is the first of a series that the researchers will conduct into safe water quality levels for cattle.
However, they’ll have to wait for COVID-19 restrictions to ease up before beginning another study scheduled to start later this month.
The three-year study is expected to test various ways of interfering with the sulfates binding with trace minerals in the rumen.
Penner said sulfates in water potentially bind with trace minerals in a cow’s rumen, making those minerals unavailable for the body to absorb and use.
Bismuth subsalicylate, for example is a common antacid found to bind with sulfides, which could help diminish the effect of sulfates in the cattle’s drinking water.
Another funded program will study beef cattle in their normal setting where wells and dugouts contain high levels of sulfates.
“Rather than artificially spiking the sulfate, we will use naturally occurring water that is high in sulfate and we will do this in outdoor conditions during summer months,” he said.
