When drought progresses and summer pastures dry up, many producers consider feeding hay. One commonly asked question is, "Can I feed hay that was left over from last year and if so, what should I be aware of?"
High-quality hay stored in a dry location can last several months with little deterioration in forage quality. Typical nutrient losses for barn-stored hay run around 5 percent during the first year of storage and very little in succeeding years. There is one exception: hay stored more than one year will suffer some loss of carotene, the precursor of vitamin A. Livestock rations may need to be adjusted to make up for this deficiency.
However, much of the hay made in Missouri is stored outside. Storage and feeding losses for outside-stored hay range from 7 to 30 percent depending on several factors. The main factors to consider when estimating storage losses for hay stored outside are bale density, storage site, bale orientation, amount of rain and snow during the storage period, and how the bales were covered or protected from the elements.
In general, the denser or more tightly hay is baled, the lower the nutrient losses. An average density of 10 pounds per cubic foot or greater is ideal. Assuming a 5 x 6 round bale, this means that bales need to weigh 1400 pounds or more to minimize weathering losses. Bales that have a density of 7 pounds per cubic foot or less (especially in the outer few inches of the bale) often look like a flat tire. These bales often have nutrient losses that are 20 percent greater than properly made bales and they should be avoided or discounted accordingly.
Hay stored on a well-drained site is best. Most of the spoilage associated with big round bales stored outside comes from hay-to-soil contact. Hay stored directly on the soil surface can be expected to have losses in the range of 15 to 25 percent from bottom spoilage alone. Hay stored on a gravel surface, or elevated on pallets, poles or other materials, will have much lower nutrient losses from bottom spoilage.
Bale orientation and placement will also affect storage losses from big round bales. Rows of bales stored in a north-south orientation tend to weather less than those stored in an east-west orientation. A north-south orientation maximizes exposure of the rounded sides of the bales to the sun, which promotes drying of the top of bales during the day. This leads to less spoilage and better quality hay. In addition, bales should be placed so that the flat ends are butted against each another. This practice protects the bottom of bales from water flowing down the slope and into the bale. Properly done this protects the ends almost as well as if they are part of one continuous bale.
The amount of rain or snow during the storage period plays an important role in nutrient losses of big, round bales. In general, the more precipitation received during storage, the greater the losses. The good news for Missouri farmers is that the dry conditions in many areas have led to lower than usual hay weathering losses. However, hay more than one year old probably has seen more than its fair share of precipitation and thus should be discounted accordingly.
Finally, how bales are protected from the elements affects nutrient losses. Bales protected with plastic sleeves or covers, tied with net wrap, or stacked in a pyramid and covered with a tarp will have weathering losses only slightly higher than if stored in a barn. Annual losses for hay covered with these materials run around 7 to 10 percent. Hay wrapped with twine only can be expected to have higher losses of 15 to 25 percent annually.
Updated 6/14/06
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