Deficiencies can result in weak calves, deformed stillbirths
Just 75¢ of a manganese supplement per cow per gestation appears to correct a manganese deficiency in dairy cows. Without it, some Minnesota producers are reporting up to 10% of pregnancies with deformed fetuses or unsteady, weak calves born live.
Low manganese is the primary suspect in causing deformities in 10 dairy calf fetuses that were submitted to the University of Minnesota Veterinary Diagnostic Laboratory (VDL) last year. The dead fetuses had skeletal deformities that included twisted or short limbs, dwarfism and shortened upper jaws that exposed the lower teeth.
In 2001, the National Research Council (NRC) lowered the manganese requirement by more than half—from 40 mg per kg of dry matter to 17.8 mg. "More recent research indicates that lactating and dry dairy cows require 1.6 and 2.7 times higher concentrations, respectively, than those calculated using the 2001 NRC model," says Jeremy Schefers, resident pathologist at VDL.
In his pathology work with the fetuses, Schefers ruled out BVD, infectious bovine rhinotracheitis
virus (IBRV), lepto, other pathogens, genetic defects, goiter, and copper and zinc deficiencies.
Many producers have shifted to higher levels of corn, distillers’ grain and corn silage during the past decade. Corn-based feed is lower in manganese than are grass hay or mixed haylage diets.
The result has been a possible deficiency of the mineral in fetuses, causing the deformities. When half a pound of manganese sulfate or manganese-amino acid complex was fed to cows during their gestation, no further problems were reported. Cost of the supplement per cow for the entire gestation period: 75¢ to $2.25.
Some anti–genetically modified organism activists have blamed glyphosate-tolerant soybeans and corn for the problem. The theory is that glyphosate interferes with the plant’s ability to absorb and utilize manganese. But several research trials have failed to document the theory.
"Manganese deficiency in corn and soybeans is not a new phenomenon and has been described for decades prior to the use of glyphosate," Schefers says. "Many want to pin this on Roundup, but I can’t get there."
- June/July 2011