Does hay lose nutritional value with age

The simple answer to this is: Yes. Hay, always and without exception, loses nutritional value with age and consequentially loses economic value as well.

The more complex issue for a horse owner is estimating how much has been lost when considering a hay purchase.

Of course the real reasons we want to know how much value has been lost are to determine the remaining nutrition in the hay for your horse and comparing relative value for various hay purchase options.

If you are a bottom line person and just want a quick and dirty answer: in Alberta hay that is stored outside without cover loses 15% of its nutritional and economic value after 12 months. If you live in a warmer or wetter area, the loss will be more. The rest of this section provides you the details involved.

There are many factors that go into determining the actual nutritional loss and there is quite a lot of science involved. While we make no claims to possess the underlying scientific knowledge and instruments needed to make an accurate forecast of loss, we can share how we at South Molton apply this clinical data in our evaluation of potential hay purchases.

Estimating nutritional loss for stored hay, like all estimates, it will require some judgment in developing your estimate of nutritional value of hay choices. The key data you will need to develop a rough estimate is:

  1. Annual rainfall for the area a potential hay purchase was grown which you can find on the web.
  2. Knowledge of how the bales are stored which you will see when you view the hay or just ask the seller.
  3. An assessment of how tightly packed the bales are. To assess this, press our hand into the bale. A tightly packed bale will hardly have any give and you will have trouble digging your fingers into it get a sample.
  4. Knowledge of when the hay was baled which you can obtain from the seller.

Below is a white paper developed by South Molton as a practical guide to determine an estimate of nutritional loss for stored hay. Our methods were determine based of the references cited below. While we could cite additional reference, most of the other references referred us back to these two as primary references and were used only to seek out other data points.

South Molton guide to estimating nutritional loss for stored hay (requires Adobe Acrobat Reader 116KB)