The Effects of Weathering on Hay

Hay is the most commonly used stored feed for livestock in the United States. Unfortunately, hay losses are equally common, especially in parts of the country where rainfall amounts are high.

Statistics tell us that on many farms, hay storage and feeding losses account for up to 10 percent of the cost of livestock production. Despite these numbers, many producers fail to realize just how much hay loss they are experiencing.

One of the biggest reasons for hay storage loss is weathering. Weathering occurs when hay is stored outside and exposed to the elements. The longer the hay is exposed to the elements, the greater the loss.

Bales that are stored outside and without any cover will experience a sharp rise in moisture content. This is particularly true for the outer part of the bale where moisture content can increase more than 100 percent! And while weathering starts off slowly, it quickly accelerates. That’s because weathered hay is more easily penetrated by rain and has a difficult time drying out.

If there is a large amount of rainfall in an area, dry matter loss from weathering can reach up to 50 percent. In the most highly weathered portion of a hay bale, almost 15 percent of the total crude protein and a quarter of the digestible nutrients can be lost. What’s more, weathered portions of hay bales are often rejected by livestock which leads to lowered intake.

Data shows that more than 50 percent of the losses that are sustained when hay is stored outside occur because bales are sitting directly on the ground. In order to reduce this weathering, hay and soil should not meet. This is true even if the ground below the bale is relatively dry. When a bale weathers on the bottom – even if it is only a small amount – the bale will flatten and allow even more of the bale to come in contact with ground. It also will cause the top of the bale to flatten, exposing it to even more rainfall.

The best way to combat weathering of hay is to store hay in barns. The reduced loss of hay from weathering will in most cases pay for the construction of a barn in only a few years. This is especially true in areas of the country where there is high humidity, a great deal of rainfall, or when the hay being stored is particularly porous.