Ask the Expert: Feeding Preservative Treated Hay

Photo Credit: Krishona Martinson, PhD, University of Minnesota

Question: Our regular hay supplier applied a preservative (propionic acid) to the bales this year. What is that and is it safe for horses?   

Answer: Preservatives are commonly used during times of frequent rainfall or poor drying conditions (e.g. high humidity or heavy dew). Propionic and acetic acids are commonly used hay preservative that are applied to hay as it is baled to allow baling of wetter than normal hay without spoiling during storage. Moisture at the time of baling is directly related to mold formation. Hay baled at ≤15% moisture is unlike to mold; however this is impacted by bale-type and mass. For example, small square bales can be baled up to 18% moisture with limited risk of mold formation; however, large round bales must be baled at ≤15% moisture to reduce the risk of mold formation. Preservatives are most effective at inhibiting mold growth, and most economical, when the hay is baled between 18 to 25% moisture. 

Preservatives are safe for use in horse hay. Researchers found that when given a choice, horses preferred hay that was not treated with a preservative; however, horses readily consumed the treated hay when a choice was not given. Yearlings receiving hay treated with a preservative consumed and gained just as much as yearlings consuming untreated hay, and clinical measures of well-being were not affected by consumption of preservative-treated hay. Interestingly, a horse’s hindgut bacteria actually make propionic acid as a result of microbial fermentation.

Therefore, feeding horses hay treated with a preservative is a safe and common practice, especially in years when poor weather conditions exist for making hay, and helps to inhibit mold growth during storage.

Written by Krishona Martinson, PhD, University of Minnesota. This and other horse nutrition articles can be found at http://www.extension.umn.edu/agriculture/horse/nutrition/.

How To Identify Moldy Hay – Ask the Expert: Testing for Moldy Hay

Our friends at the University of Minnesota Extension have helped to answer the question, how do you know if your hay is moldy? Equine expert Krishona Martinson, PhD, offers some tips below when it comes to hay testing.

Question:  I recently purchased some hay. I thought it was good quality, but I think the hay might be a little moldy. Can I test my hay for mold?

Response: Most forage testing laboratories can test hay (and other feed stuffs) for different types and amounts of molds. The costs average $40 and takes about one week to complete. The sample is collected and submitted similar to a hay analysis for nutrient value.

Watch a YouTube video on how to collect a hay sample.

All hay will have some mold; no sample will have zero mold. Mold spore counts are given in colony forming units per gram (cfu/g). Hay with less than 500,000 cfu/g of mold is considered good quality.

Hay with 500,00 to 1 million cfu/g is relatively safe, while hay with over 1 million cfu/g of mold should not be fed to horses due to the risk of respiratory issues. Most people can start to detect mold around 500,000 cfu/g.

If your hay is between 500,000 and 1 million cfu/g of mold, use precaution by pulling flakes apart before feeding, feeding outside or in a well-ventilated area, using a hay net to restrict the horses ability to bury their nose into the hay, and wetting the hay to reduce the amount of mold spores inhaled.

Alternatively, you could look for a better quality hay or ask your hay supplier to exchange the hay for bales with a lower mold count.

This article is reprinted with permission from Krishona Martinson, University of Minnesota. This and other horse nutrition articles can be found at http://www.extension.umn.edu/agriculture/horse/nutrition/.

Judging Hay Quality for Horses

Because hay is such a common part of a horses diet, judging quality on visual inspection is important, as lab analysis is not always easily available.  Here are three simple things to look for to help you select the best hay for your horses and your money.

  1. The initial check that most people are familiar with is color and smell.  Horse hay should be bright green and smell slightly sweet.  Brown hay indicates either a problem in the baling process, such as being rained on, or age.  Acrid or musty smells generally indicate the presence of mold.
  2. Another sign of good horse hay is the leaf:stem ratio.  The more leaves, the better, since the leaves are where most of the nutrition in the hay is stored.  Hay that has too many hard, woody stems is difficult to digest.  Even if it cheaper, most horses will pick through and leave the bulk of the stems behind, costing more in the long run.  High quality hay is fine-stemmed, pliable, and full of leaves.
  3. Type of hay is another factor.  Grass hays, such as timothy or orchard grass, generally provide sound basic nutrition.  The higher the concentration of legumes, such as alfalfa or clover, the higher the energy content.  High quality alfalfa is generally better than high quality grass hay, but good quality grass hay can be better than average quality alfalfa hay.

The best thing, in the end, is to have hay tested.  This is not always feasible for every load, but if your hay source is consistent from load to load, this may be a good option to get a general feel for what nutrients your hay contains.