Nitrates in Horse Hay

The following article is written by Monique Warren, the owner of Hay Pillow Inc. Monique has been an equine guardian for forty years, and studying equine nutrition and horses feet is her passion. She resides in Southern California.

horse hay

Nitrates In Hay Exposed

The purpose of this article is to inform equine guardians of the potential for unhealthy levels of nitrates in horse hay to increase awareness that will lead to change. You can’t see smell or taste nitrates. They can lurk in the prettiest, greenest best smelling bale of hay. The only way to know the levels you are feeding is to test your forage. It is optimum to test prior to purchase.

After being introduced to the practice of testing hay prior to purchase ensuring low sugars and starches and formulate a custom supplement to balance the major and trace minerals, I thought I had all bases covered nutritionally. I would buy enough hay to last a year. During the second year of this practice, my horses were not doing well. My mare was out of breath on a 20 minute hike; her allergies were the worst they had ever been. My gelding had old scars reappearing from years previous that the hair had fully regrown back in after healed.

When my vet came out for annual dental work and drew back the syringe to administer an IV sedative, his blood was dark and brownish. When searching for answers, it was suggested that I test my hay for nitrates. The results came back 4,700ppm and they had been ingesting the same hay for 7 months.

What are Nitrates?

Nitrogen is one of the main chemical elements required for plant growth and reproduction second to water. When more soil nitrogen is present than needed for optimum growth, the plant can store what it does not utilize. Nitrate levels can increase to toxic levels in forages any time the nitrogen supply in the soil exceeds the nitrogen needs of the plant.

Nitrates can be present in high levels due to over fertilization or triggered by environmental stress such as drought, freeze or even cloudiness, where plant growth is restricted but absorption of nitrate from soil continues. Irrigation by water high in nitrates, run off from other water sources, certain herbicides and deficiencies of essential nutrients like phosphorus, sulfur and molybdenum can also contribute. Improperly cured or stored bales of hay with too much moisture; bacterial action can convert available nitrate to nitrite which is 7 to 10 times more toxic than nitrate. Never assume that organic equates to low levels, over fertilization from any nitrogen source and poor field management can occur in any crop.

Nitrate is converted to nitrite in the large intestine of the horse. Nitrites in blood oxidize the iron atoms in hemoglobin from ferrous iron (2+) to ferric iron (3+), thus compromising the ability to supply oxygen to tissues in the body. Nitrite converts to ammonia, if there is more nitrite than can be converted it leads to hypoxia (deprivation of oxygen supply).

The result is Acquired Methemoglobinemia; a blood disorder in which an abnormal amount of methemoglobin (a form of hemoglobin) is produced. Hemoglobin is the molecule in red blood cells that distributes oxygen to the tissues. Methemoglobin cannot release oxygen.  It occurs after exposure to certain chemicals and drugs, including nitrates. In simpler terms, your horse’s tissues are being suffocated to some extent depending on exposure.

Symptoms of Nitrate Poisoning

Clinical signs from sudden ingestion of highly toxic levels may include difficulty breathing, weakness, tremors, ataxia, rapid heartbeat, foaming at the mouth, grey/blue or brown discoloration of blood and tissues, seizures, and rapid death. Abortion can occur in animals that survive the initial clinical signs. Chronic exposure to lower levels of nitrate has not been well researched in horses. Associations between chronic nitrate exposure and infertility, poor growth, hypothyroidism, frequent urination and other disorders have been claimed. Minimizing nitrates in the diet is the most logical “cure” to these symptoms. We want our horses to thrive, not just survive.  Knowing that nitrates deprive the tissues of oxygen affirms they are of no benefit.

“Safe” levels of nitrates are certainly debatable and published within a variety of ranges. For unadapted animals averaging 2,500ppm, slight risk (feed as 50% maximum of total forage for pregnant animals) with 2,500-5,000ppm, moderate risk (feed as no more than 50% of diet, not safe for pregnant animals). These levels are not necessary. In fairness to the growers, it would be impossible to produce crops at less than 1ppm on a consistent basis. I don’t think it unreasonable to require less than 1,000ppm to send any crop to market. The growers I purchase from are consistently less than 500ppm. The test results also indicate well balanced soil with ideal calcium; magnesium and phosphorus ratios.

Nitrate Accumulating Plants

Some plants are known accumulators of nitrates such as Fescue and Johnson grass, Barley, Flax, Sudan grass, Sorghum, Sugar beets, Soybean and Wheat. Non-accumulators include Bermuda, Rye, Fescue, and Orchard grasses.  None though are immune to high levels of nitrates.

Fields that are flood irrigated tend to be more risky in regards to pre-purchase tests. The lower lying areas in the field can be especially high in concentrations while the higher parts of the field are at acceptable limits. I tested 12 bales of hay from the top of a block of 82, the results were 800ppm prior to purchase, bought 60 bales from the same block and re-tested. It was 4,500ppm. The only way to know is by testing the actual hay you are buying, even if it the same field or stack.

Nitrate Test Results

Test results can be very confusing and difficult to decipher. For simplicity purposes use the % nitrate number. If results show % of nitrate at .30, multiply by 10,000 to convert to ppm (.30 X 10,000 = 3,000ppm).

I have tested my hay for 5 years and reviewed numerous results from other sources. Nitrate test results have been as high as 6,500ppm and less than 1ppm. Which one would you choose if you had the choice? You as the consumer do have a choice. Ask your grower or feed store for a hay test including nitrates or test it yourself prior to purchase.  The majority of horse owners take great pride in reading nutritional analysis labels of supplements and bagged feeds. Would you buy a bag of feed or supplement without a label? A nutritional analysis should accompany the hay you purchase for a multitude of reasons including but not limited to nitrates, sugars, starch and protein, major and trace minerals.

 

References:

A.D.A.M. Medical Encyclopedia. Methemoglobinemia.

Whittier J.C. (2011). Nitrate Poisoning.

Casie

Hi! My name is Casie Bazay. I'm a mom, a freelance writer, and a certified equine acupressure practitioner.

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9 Responses

  1. Robynne Catheron says:

    Good article, thank you for sharing it. Does Ms Warren have any recommendations to the hay growers to help reduce the risk of high nitrates, and/or ensuring consistency in all mows and fields?

    • As the article explains: Nitrates can be present in high levels due to over fertilization or triggered by environmental stress such as drought, freeze or even cloudiness, where plant growth is restricted but absorption of nitrate from soil continues. Irrigation by water high in nitrates, run off from other water sources, certain herbicides and deficiencies of essential nutrients like phosphorus, sulfur and molybdenum can also contribute.

      Well balanced soils in regards to the major minerals; calcium, phosphorus and magnesium certainly reduces the risk and reduces the supplementation to balance the hay.

      The higher results I experienced were with Bermuda hay. Bermuda is a perennial grass, IOW those fields can be cut for years w/out a rotation of crops. Over fertilizing seems to be the majority of the culprit. The growers equate a higher yield to more fertilizer. This is not the case. Numerous studies have been done to prove this, more is NOT better! If the soil is not loamy allowing for proper drainage, the nitrogen can continue to build in the soil. Flood irrigating seems to be the worst. Here in Imperial Valley, the soil is more clay equating to retention of any additives to the soil.

      Also, some farmers will refrain from watering just prior to cutting to speed up the curing process. Drought conditions will drive the nitrates up.

      Happy to answer any other questions. Monique

    • Michele says:

      Nitrate Accumulating Plants

      Some plants are known accumulators of nitrates such as Fescue and Johnson grass, Barley, Flax, Sudan grass, Sorghum, Sugar beets, Soybean and Wheat. Non-accumulators include Bermuda, Rye, Fescue, and Orchard grasses. None though are immune to high levels of nitrates.

      Tell me what Fescue is….accumulator or non- accumulator?

    • Monique Warren says:

      It is helpful for the growers to test their hay and soil prior to fertilizing. Soil needs to be monitored on a continual basis. Especially with fields that are not crop rotated.

  2. Suzi Parr says:

    Is nitrate testing separate from the typical hay test? We’ve tested with Equi-Analytical labs and I don’t see nitrates on the standard results. The symptoms you listed above sure sound like the same that one of our horses experienced last winter. We’re not using that hay this year but are kind of wondering if we can figure out last year’s issue.

    • Not included in any of the packages. On their website click on services and then sample information sheet.choose nitrates on the first and second page. It is $9.00 additional.

  3. Heidi says:

    I love your article. I also have been following this topic. They do not know the sub clinical symptoms. That is the frightening part. Cattle people dilute with grains, and vitamin A. I also use low doses of vitamin A, E, and C. We are in a drought here in California, and my horse’s started to have problems in August, 2013. The vitamin A , E, C, and plain salt helped a lot. They have linked Laminitis to Nitrite poisoning, which was the first symptom my horses got. Vitamin A really helps this. I only use the human pills of vitamin A in fish liver oil form, d-alpha vitamin E. My horses took care of the vitamin C, they started to eat oranges during this, smart guys!!!! Thanks for the info. I have my BS in Ag/Animal Science, and have also furthered my research over 25 years. If you have more data, I would love it.

  4. Karin says:

    Thank you for this information! Nothing I’ve ever heard about in Sweden. Now I understand that my pony has been nitrate poisoned in a bad way.

    Is there any hope of him ever getting better? Right now one single straw of grass get his feet sore. In your experience, will he stay this way or improve? He is no longer short of breath or have swollen eyes, but I feel it’s always “round the corner”.

    My hay has 4,72g/kg and from what I can understand it is the sames as Moniques was. He now gets a little bit hay, but mostly straw (barley, just the straw).

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