Understanding Hay Quality – Part I

Since hay is the biggest part of our horses’ diets, it’s important for us to understand what hay means to our horses nutritionally and to understand how to judge hay quality. We’ll be looking at both in this three part series on hay quality.
To start with there are a few terms we need to define:

  • MCal/lb – Mega Calories per Pound, a measurement
  • ADF – Forage digestibility measured by the level of acid detergent fiber (cellulose and lignin)
  • NDF – Neutral detergent fiber a measure of cell wall content

There are two excellent articles on hay quality that I will be drawing on throughout this series:

Most of us were taught to choose hay based on old, antiquated standards of what color the hay is and what it smells like. Livestock owners have been using more scientific methods for determining what to feed their animals, scientific methods that can easily be applied to choosing hay for our horses.
Hay Quality 2One of the biggest misconceptions about choosing good hay is the color of hay. Green does not necessarily equate to good nutrition. While the vitamin A precursor in plants is greater when hay is green and the beige color is an indication of sub-bleaching and leaching of nutrients by rainfall that occurred after harvest, color is a poor indicator of forage quality as bright green weeds can be less nutritious than brown alfalfa.
Quality is an expression of characteristic that are going to affect the horses performance and health. You should judge the quality of hay on multiple characteristics. Below is a quality standards chart from the Hay Market Task Force of the American Forage and Grassland Council.
Prime hay and quality standard 1 hay are of no real value to horse owners except as reference points. Quality standard 2 hay is ideal for growing colts, lactating mares, and horses in heavy work.
Most horses in the US should be fed quality standard 3 and 4 hay are the more typical horse needs in American today. Quality standard 5 hay is a standard filler grade hay and can be fed safely as a base feed to all horse grades. As a reference, the best possible pure timothy hay can never be over about 10% crude protein.

Quality Standard Crude Protein Acid Detergent Fiber Neutral Detergent Fiber Digestible Dry Matter Dry Matter Intake as % of Body Weight Relative Feed Value
Prime >19% <31% <40% >65% >3.0% >151
1 17-19 31-35 40-46 62-65 2.9-2.6 151-125
2 14-16 36-40 47-53 58-61 2.5-2.1 124-103
3 11-13 41-42 54-60 56-57 2.0-1.7 102-87
4 8-10 43-45 61-65 53-55 1.6-1.3 86-75
5 <8 >45 >65 <53 <1.2 <75

In Part II of Understanding Hay Quality, we’ll look maturity, species and variety, leafiness, and harvesting. In Part III, we’ll look at meeting nutritional requirements, forage testing, purchase, and storage.

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