Horses and Safe Limit of Nitrates from Dairy One, Was Grass Hay with High Protein

Debra Trujillo

I thought the group may be interested in this.  I ran into some more hay after the thread on "Grass Hay With High Protein" that was straight orchard with protein at 15.8%, but had very low ESC/starch numbers (5.4 and .7).  The hay grower had already sent in a sample to Equi Analytical for a NIR test, so I called and asked if I could get them to run nitrates on that.  They did and I got the results today.  The wet chemistry protein came back as 15.7% (very close to the NIR figure) and the nitrates (DM basis) was .73, PPM Nitrate-Nitrogen 1658.  There was a comment:  Nitrates by RQ Flex.  
I won't be buying this hay. 
Dairy One included information on Nitrates and Dairy Cattle which also had the table of nitrate levels and comments on what is safe and what is not, starting with <.44 and ending with >1.76 (close to what is in Files).  But, there was a statement at the end of the document that says "HORSES are more tolerant of nitrates than cattle.  A practical upper safe limit is 1.5% Nitrate or 3450 ppm Nitrate Nitrogen."  My thought was Wow, that's awfully high.  Surprised me, to say the least, from what I have read on Nitrates in the files.  What are thoughts here?  Would they make a statement like that without some research on the subject?
Debbie and Precious
June 2017, Parker CO
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Hi, Debbie.
Thanks for the follow-up. 

So we know a couple of things from these results. First, the "high protein" isn't really all crude protein, whether tested by NIR or wet chemistry. Crude protein testing is registering the high nitrate. I have a formula somewhere -- I won't torture you with it-- that deducts nitrates from the crude protein to arrive at an closer estimate of the real crude protein. 
Second, yes, horses do consume hay with high nitrates. Sometimes that's the only hay available, it looks nice, and no one is the wiser. Here one local feed store that does no testing on their hay sells high nitrate hay all winter long. What "high" means isn't black and white. Does it mean equines that eat it aren't adversely affected? We'd love to see scientific evidence of that. One thing that's reported in this area every year is spring abscesses in non-IR/non-PPID horses. It's a mystery blamed on wet and muddy conditions. Or could it be a winter of eating hay with nitrate levels like those in your sample? We don't know.

The best way to answer your last question is to call Dairy One and ask customer service if they would please give you the research supporting their claim. They are usually very helpful. 

Cass, Sonoma Co., CA 2012
ECIR Group Moderator
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Eleanor Kellon, VMD

Those levels (which are NOT backed by formal research) refer to acute toxicity -   i.e. animals dropping dead, aborting, etc. Effects of lower level intake have not been studied in horses. Of particular interest to us is effects on thyroid function and laminitis. For many years Fescue endophyte was said not to affect horses' feet - until it was actually studied and found that it does.  Nitrate intake has also been reported to cause hoof pain, but not officially "proven".
Eleanor in PA 
EC Owner 2001


HI Debbie,

I am just hoping on here to say way to go above and beyond!!!! I love the enthusiasm and of course you spreading your news. This is so important to do, because many horse people (owners, vets, farriers alike) do not 1. do this and 2. do not KNOW how it can affect a horse! So kudos to you! You are helping us all learn a little something that we can take with us, to hopefully help another horse wether you know it or not. 
PS- Glad you won't be buying that hay!

~ Candice 

Primary Response Team

September 2018, Summerfield, FL

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