CORVALLIS - Some Oregon dairy cows that have just calved are suffering from nutritional disorders, and an Oregon State University scientist is looking for volunteer farmers to help her find out why.
The cause of the problems could be too much potassium in cows' diets, coming from pastures fertilized for years with manure and waste water.
Or the cause may be more complicated, said OSU dairy scientist Diane Carroll. "We have a lot of dairy farmers who feed high-potassium forages to their cattle, and many have few nutritional disorders in their herd."
To help pinpoint the cause, OSU is looking for a few volunteers.
"We want 10 dairy farmers who feed high potassium levels to their cows -five with high metabolic problems and five with low," Carroll said. "We'll study their operations for two years, monitoring diets and health and reporting successful strategies to the dairy industry."
Interested dairy farmers can call Carroll at 541-737-1898.
For Carroll, the disorders are close to home. Cows at the OSU Dairy Farm are experiencing them: milk fever, twisted stomach and retained placenta after calving. "Our concern is not just treatment expense or milk production loss," she said. "We just don't want to see a cow sick."
Analysis of the forage for the ailing OSU cows showed potassium levels around four percent - two to three times what would normally be expected. "The source of the extra potassium appears to be coming from pastures that have been fertilized for years with manure and waste water," Carroll said.
Using pastures to dispose of dairy waste is generally thought of as an efficient way to put nutrients back in the soil, Carroll said. But after 10 to 20 years of doing this, potassium levels are getting excessively high.
Forage plants such as orchard grass and perennial rye tend to take up much more potassium than they need to grow, and the excess gets eaten by the cows. Over-fertilization with manure just wasn't an issue that had come up before, Carroll said. It was thought of as a sustainable practice.
"Dairy farmers may just need to adjust management practices to keep the dry cows off these high potassium forages, so they don't get sick after calving," she said.
Another strategy would be to manage manure more efficiently.
"Most of the potassium is in the cow urine, so applying only dry solids to some pastures to be used by dry cows may reduce the problem. Another option is to harvest the grasses in the pastures furthest away from the barn for dry cow feed. Some studies show that these tend to have been less heavily fertilized," she said.
"Harvesting the affected pastures without adding potassium fertilizer is an option," added Carroll, "but research estimates are that it would take 10 years for the potassium soil to go back down to normal levels."