With the limited opportunities and short windows many have had to make hay so far this year, some hay may have been made at higher moisture levels than we would like. Moisture levels have a direct effect on hay quality. What we have found to be a consistent number in the literature is 20% moisture maximum. To be more specific:
- Small squares to be 20% or less,
- Large round, 18% or less and
- Large squares, 16%
Hay baled at 20% moisture or higher has a high probability of developing mold, which will decrease the quality of hay by decreasing both protein and total nonstructural carbohydrates (TNC) AKA energy! The mold will also make the hay less palatable to livestock and could potentially be toxic, especially for horses. Even hay baled between 15%-20% moisture will experience what is known as “sweating.” Sweating, in regard to hay bales, refers to microbial respiration, which will create heat and result in dry matter (DM) loss. A good rule of thumb is that you should expect a 1% DM loss per 1% decrease of moisture after baling. As an example, hay baled at 20% moisture that is stored and dried down to 12%; will result in 8% DM loss.
What happens if we bale hay and the moisture content is too high? Bad things. If lucky, maybe the hay will only mold, but if it is too moist and starts heating, it could catch fire. If the hay heats to 100-120 degrees F, it will be fine; if it goes above that, monitor daily. Once it gets to 140 degrees F, consider tearing down the stack. At 150-160 degrees F, call the fire department, and once it gets to 160 degrees F, there will be smoldering pockets and hot spots, and gases will ignite hay when exposed to air (source: Washington State University Extension, Steve Fransen and Ned Zaugg).
It can be a double edged sword in regards to losing quality by not baling, or losing quality by baling with moisture levels that are too high. Therefore, our recommendation to ensure adequate livestock nutrition this winter is to have a forage analysis done on the hay baled this year. Once you have those results, develop a corresponding supplemental feed program, if necessary, based on the nutritional requirements of your livestock.
The two short videos below by Clif Little and Rory Lewandowski will answer questions regarding forage testing, and subsequently interpreting the results of the test(s).
Source: Ohio Beef Cattle Letter