The rain during the early summer of 2008 has been wonderful for the recovery of drought-damaged pastures, plant growth and replenishment of moisture in the soil profile, but has hurt hay production. When plants are cut for hay, they do not immediately die. As long as moisture is above 40 percent, they will continue to respire - exchange oxygen and carbon dioxide - a process that burns energy. In a study at Texas A&M Overton Research Station, Coastal bermudagrass went from 11.1 percent crude protein (CP) and 51.6 percent total digestible nutrients (TDN) to 8.9 percent CP and 42 percent TDN at baling after two days of drying.
When drying conditions are poor, the period of time that plants can continue to respire after cutting is extended. This can lead to even greater losses in quality and a loss in dry matter.
The timing of when rainfall occurs after cutting will also influence quality. If rain occurs immediately after cutting, the plant cells are still relatively turgid, or firm, from retained water, and, though some losses will occur, little moisture will enter the cells and leach the water-soluble cell contents. If plants have been drying a couple of days and then are rained on, plant cells will re-absorb moisture and greater leaching of cell contents will occur. In addition, drying will make plants somewhat brittle. If hard pounding rains occur, leaves can be broken off, which will also lead to dry matter losses and a drop in quality.
Sometimes, rain will not reduce hay quality significantly if the hay has adequate time to dry and cure prior to baling. The only way to know for sure, though, is to test the hay. This simple task is even more important this year. If, however, moisture was an issue at the time of baling, pulling a test immediately may not be as accurate as waiting to test after the bale has gone through any changes due to moisture.
In the rush to get hay baled in between rains this year, some hay may have been baled with extra moisture. The effects we see in the windrow can occur in the bales packaged at greater than 20 percent moisture levels. At these moisture levels, there will be an increase in mold, which leads to animal refusal and increased dry matter losses. If mold has occurred, it is also a sign that a drop in energy has taken place as the sugars (energy) in the hay have been used to fuel the growth of the microbial population. In extreme cases, temperatures can rise in a bale to the point that a portion of the protein becomes bound to the fiber fraction of the plant cell and is essentially unavailable to the animal consuming it.
Storage of bales is also critical, as anything that can be done to reduce the amount of degradation or spoilage of the hay is beneficial to the cow and to the bottom line of a beef operation. In a 66-inch-diameter round bale, 59.5 percent of the total quantity is in the first 12 inches. Round bales that are stored outside typically show discoloration and some degree of degradation at least 6 to 7 inches into the bale.
High moisture bales tend not to store very well as they undergo heating, and dry matter losses occur. These bales will lose their shape, making them more vulnerable to damage from subsequent rain because they will not effectively shed water. Using net wrap or covering bales with a tarp will help shed moisture off the tops of the bales and reduce chances of additional damage.
Take additional precautions with hay that is exposed to the elements, as unstacked bales stored outside and in direct contact with the ground will suffer the highest degree of degradation. Placing round bales in well-drained storage areas in a north-south orientation with at least 3 feet between rows and bales placed end to end within rows will allow air and sunlight to pull moisture from the bales. Placing round bales on some type of barrier, ideally either gravel or pallets, between the ground and bale will decrease the wicking of moisture from the ground into the bottom of the bale.
Ultimately, storing hay inside a barn greatly reduces hay losses. Storing high-moisture hay in a barn still comes with some risk. If high-moisture bales are stored inside and their internal temperatures exceed 170°F, fire can occur. To reduce the risk of fire, temperatures of high- moisture bales that are stored inside should be monitored for at least 15 to 20 days.
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