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Dan C., DVM
Dan C., DVM, Horse Veterinarian
Category: Horse Veterinary
Satisfied Customers: 1180
Experience:  Solo Equine Practitioner/Mobile Practice Owner for 16 years.
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the advice you gave me was incorrect. Glyphosate will harm

Customer Question

the advice you gave me was incorrect. Glyphosate will harm horses.
Submitted: 8 years ago.
Category: Horse Veterinary
Expert:  Dan C., DVM replied 8 years ago.
Hi, Horsesandmichelle:

Thanks for getting back to me with your concerns. If I can be corrected, I'm always glad to know, especially if it is concerning a toxicity, etc. Can you please give me the reference that cites the harm that glyphosphate causes in horses? I've double checked references and can't find any such data, so I'd be glad to have that information. I'm attaching a recent MSDS sheet concerning glystar/glyphosphate, and according to the manufacturer, chances of toxicity from ingestion are very low, and would require an extreme amount to cause even minor illness, and this comes from the results of testing in a variety of species.
My apologies if I've given out incorrect information, and I'm looking forward to hearing from you.

Customer: replied 8 years ago.

Dr. Dan,

I have compiled quite a large file on this. Unfortunatly, in the US there are not alot of studies that have been conducted by sources other than the manufacturers(ugh, I hope I spelled that correctly). But I have been able to find studies done in other countries


The main ingredient of Glystar is glyphosate, which in itself is not necessarly toxic, when other ingredients are mixed in ie, the surfactant, that is when we run into problems. It seems that the combination and dose is the problem.


The spray was put down directly where I feed, without my knowledge. In fact, it was done three times. The woman used 5 gallons of glystar in approx. 300 gallons of water to treat less than 1/4 acre.


My horses are exhibiting muscle wasting, poor hair coat, inability to gain weight(they are 14 months old and are the size of 5 month old colts), lethargy, bouts of diaharia. The blood work shows liver, kidney problems. All have been fed the best hay(tested), have had mineral blocks with selinum and wormed on a regular basis.


I have lost one mare and am getting ready to send the three foals off to the University.

Expert:  Dan C., DVM replied 8 years ago.

Thanks for getting back to me.


I'm sorry for yur loss, as well as the ongoing problems that certainly seem to be related to the chemical use. What you describe does sound exceedingly high. Again, if you could get me references on what you have uncovered, I'd greatly appreciate it, and I'm glad to help in any way I can.


Thanks again,