Gray hair and wrinkles may be defining features of old age, but I’ve heard those characteristics also come from stress, anxiety, and raising rowdy kids. Similarly, quality loss in older hay is not necessarily a matter of bale age; it’s a reflection of handling practices and the environment in which bales are stored.
In a recent issue of the University of Nebraska Extension’s BeefWatch newsletter, Ben Beckman, Jerry Volesky, and Daren Redfearn suggest that when stored properly, hay can be adequately preserved for years — maybe even decades.
“Time alone does not drive hay quality decline — storage conditions do,” the extension specialists write. “Age is really a proxy for how long hay has been exposed to moisture, oxygen, and physical handling. Those factors determine whether quality is largely preserved or steadily declines.”
When forage is baled at target moisture levels and stored indoors, decomposition is limited and hay quality can be maintained long term. However, the specialists note that most bales are exposed to some degree of moisture and heat during storage, encouraging dry matter loss.
“Losses occur through microbial respiration, weathering on the outside of bales, leaching of soluble nutrients, and physical loss during handling,” the specialists write. “This dry matter loss sets the stage for most of the quality changes we associate with older hay.”
Energy and protein
Not only are soluble carbohydrates the most digestible components of forage for livestock, but they are also the most readily available energy source for microbes. When elevated moisture encourages microbes to respire, total digestible nutrients (TDN) decline and fiber makes up a larger percentage of the remaining forage.
“Over time, this shift leads to lower digestibility and reduced energy availability, and TDN tends to decline fairly consistently, especially when hay is stored outside, exposed to precipitation, or in contact with the ground where moisture can wick into the bale,” the specialists state.
Crude protein (CP) loss is a little more complicated. The specialists note that CP can be physically lost when high-quality plant parts are damaged or removed during baling or handling. For example, leaf shatter in alfalfa hay drives CP content lower. Crude protein can also decline when soluble nitrogen compounds leach out of hay if bales repeatedly get wet.
In addition to leaching, excess moisture can lead to heating as microbial activity ramps up. This causes another type of CP loss in hay as forage protein binds to fiber, also known as the Maillard reaction. “In these cases, crude protein may still appear normal on a forage test, but protein availability to the animal is reduced,” the specialists write.
With that said, crude protein is measured as a percentage of dry matter and is based on nitrogen concentration. “If a bale loses dry matter primarily from sugars and other digestible energy components, crude protein concentration may remain unchanged or even appear slightly higher on a forage test,” the specialists explain. “This does not mean the hay improved. It simply reflects that the total dry matter has shrunk while nitrogen losses were proportionally smaller.”
Sorting limits intake
Feeding behavior can further impact the quality of consumed forage as cattle sort around weathered and moldy hay. Although sorting eliminates low-quality material, this can represent a large portion of allocated hay, depending on bale type and storage practices. For instance, round bales that are stored outside can experience significant quality loss to the outer layer, which comprises up to one-third of the total bale.
“As a result, forage tests may overestimate feeding value because they represent the bale average, not what cattle actually consume,” the specialists write. “Intake declines, waste increases, and energy and protein intake can be substantially lower than ration calculations suggest.”
Even so, sorting isn’t always a bad thing. The specialists suggest that sorting can be viewed as a management tool when farmers feed low-quality hay since animals will avoid undesirable forage that could otherwise cause intake or health issues.
“The key trade-off is recognizing that sorting shifts the system from maximizing feed efficiency to managing risk,” the specialists state. “When producers are willing to accept some waste, sorting can reduce the likelihood of cattle consuming problematic material while still capturing value from the better portions of the bale.”
Overall, if you feed hay that has spent an extended period in storage, be aware of the dry matter loss and quality decline those bales may have incurred. Test hay and observe livestock to estimate the nutrient density of older bales.
