Q: Does hay lose its nutritional value while in storage?

A: Hay begins to lose its nutritional value at the time of cutting and continues to lose nutrients both while drying in the field and while in storage. The nutrients most affected by harvesting and storing are vitamins. Conversely, the protein and mineral content of hay is quite stable. All green parts of growing plants are rich in carotene and, therefore, have a high vitamin A value. In fact, the degree of greenness is a reliable index of vitamin content. Approximately 50% of the vitamin A in hay may be lost during the first 24 hours of the curing process. If the hay is subjected to rain or other weather damage, vitamin losses are greater. Vitamin depletion continues during storage, with the rate of destruction determined by temperature, exposure to air and sunlight, and length of storage. When hay is stored under average conditions, vitamin content can be expected to decrease by approximately 7% per month. If hay is left outside, without cover, the vitamin losses will be more substantial. Again, the color of hay is the best, non-laboratory means of determining vitamin content. The greener the hay, the higher the vitamin level.

Q: When buying horse hay, what nutrient ranges are acceptable?

A: The only reliable method to determine nutrient content of hay is laboratory analysis. When interpreting results, the following guide will provide acceptable nutrient ranges. Remember, along with chemical quality, hay should also be of good physical quality.

Hay Buying Guide Based On Acceptable Ranges in Chemical Quality For Three Different Hay Types (DM Basis)

Nutrient Grass Hay Mixed Hay Legume Hay
Dry Matter (%) 90 - 95 90 - 95 90 - 95
Crude Protein (%) 8 - 14 12 - 16 > 16
ADF (%) < 40 < 40 < 34
NDF (%) > 55 > 40 > 35
Calcium (%) 0.25 - 0.65 0.6 - 1.2 1.2 - 1.8
Phosphorus (%) 0.15 - 0.35 0.2 - 0.4 0.15 - 0.35
Copper (ppm) 6 - 15 6 - 15 6 - 15
Zinc (ppm) 15 - 40 15 - 40 15 - 40

Read our Hay 101 article to learn more about selecting hay and determining hay quality.


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