Q: Last fall, we did a 'burn down' on some hay ground using Roundup. We have a buyer for the hay, except the buyer heard that you should not feed hay that's been sprayed with Roundup, unless harvest was 6 weeks post application. Is this true and why?
A: There is usually a 4 day to 8 week harvest restriction on glyphosate (Roundup). Glyphosate is the active ingredient in Roundup and there are many formulations and companies that produce a glyphosate product. The range of 4 days to 8 weeks depends on the herbicide formulation; you must read the label to find this information.
Glyphosate is a slow acting herbicide that is translocated throughout the plant. The harvest restriction allows time for the herbicide to dissipate from the forage. If hay is harvested before the recommended harvest restriction, the harvest is 'off label', illegal, and not recommended. If the harvest restrictions were followed, then the hay is safe for horse or livestock consumption.
In Minnesota, we have seen both environmental (contaminated manure) and animal health issues with other herbicides when the grazing and harvest restrictions were not followed. It is important to read and following the entire herbicide label prior to making an application.
By Krishona Martinson, PhD, and Julie Wilson, DVM, University of Minnesota