ARS | Publication request: Common obstacles to making quality hay

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 19, 2012
Publication Date: January 7, 2013
Citation: Coblentz, W.K. 2013. Common obstacles to making quality hay. Meeting Proceedings. January 6-9, 2013.

Interpretive Summary: One of the most common problems faced by hay producers is how to manage hay production schedules around unfavorable weather. This problem is particularly frustrating throughout the spring and early summer when the probability of rainfall events generally is greatest. Inevitably, some forage crops are damaged by unexpected rainfall events each year, and producers often inquire about the effects of unexpected rain damage, and what impact this may have on subsequent animal performance. Rain damage reduces forage quality by leaching cell solubles (mostly sugars) from the forage, thereby leaving more fibrous hay that has lower energy density. It also will be consumed less readily by livestock than undamaged hays. The simplest solution to this dilemma is to delay harvest until optimum weather conditions exist, but this approach also has a cost, because plants continue to mature during harvest delays. Furthermore, hays are often baled before they are dry enough to ensure safe storage; as a result, they heat spontaneously. Generally, this occurs because of producer error or miscalculation, or in an effort to avoid oncoming rainfall events. Within a given bale type, initial bale moisture is the primary driver of spontaneous heating in hay. In addition, larger hay packages are much more susceptible to spontaneous heating than traditional (< 100-lb) rectangular bales. Heating during hay storage oxidizes sugars, thereby resulting in greater concentrations of fiber components and reduced estimates of energy density. While producers cannot control the weather, a good understanding of these interrelated concepts will support good management decisions, and provide a sound basis for managing risk. This article is a summary of best management practices for making hay and is based on several research studies.

Technical Abstract: Many obstacles are known to limit the production of high-quality hays. Among these, advanced plant maturity, rain damage during field wilting, and spontaneous heating during bale storage are most common. Rain damage reduces forage quality by leaching cell solubles (mostly sugars) from the forage, thereby leaving more fibrous hay that has lower energy density. It will likely be consumed less readily than undamaged hays. Wetting also may reactivate respiratory processes that also consume sugars. Spontaneous heating occurs when hays are baled before adequate desiccation has occurred to ensure safe and stable storage. Within a given bale type, initial bale moisture is the primary driver of spontaneous heating in hay. In addition, larger hay packages are much more susceptible to spontaneous heating than traditional (< 100-lb) rectangular bales. Heating during hay storage oxidizes sugars, thereby resulting in greater concentrations of fiber components and reduced estimates of energy density. While producers cannot control the weather, a good understanding of these interrelated concepts will support good management decisions, and provide a sound basis for managing risk.