Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 5/1/2013
Publication Date: 9/9/2013
Citation: Coblentz, W.K., Muck, R.E. 2013. Effects of rain damage on wilting forages. Agricultural Experiment Station Publication. Vol. 15. No. 7.
Technical Abstract: One of the most common problems faced by hay or silage producers is how to manage production schedules around unfavorable weather. Inevitably, some wilting 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 forage quality, silage fermentation, and animal performance. Initially, it is important to remember that any decision to delay harvest of hay or silage while waiting for favorable weather is never made without cost. Forage plants continue to mature during harvest delays. This results in hays and silages with greater concentrations of fiber, and poorer energy densities. These forages often will be consumed less readily by livestock. During rainfall events water-soluble carbohydrates or sugars (WSC) are leached from plant tissues, resulting in significant DM losses. Sugars are assumed to be 100% digestible, and are the principle substrate for silage fermentation (production of lactic acid). Therefore, energy is lost from the forage, and the suitability of the forage for silage fermentation may be compromised. Generally, rain damage is much worse for dry forages compared to wet forages, largely because hydrated plant tissues retain some internal physiological control, thereby limiting significant leaching of WSC. Rain damage or poor drying conditions normally extend wilting times, which also causes losses of WSC through extended or reactivated respiration. When ensiling rain-damaged alfalfa, producers should consider wilting forages to < 60% moisture, and using a silage inoculant formulated to support production of lactic acid. It also is advisable to ensile rain-damaged forages separately from forages without rain damage, and then plan to feed rain-damaged silages before forages ensiled under good conditions. These safeguards will likely decrease the risk of unsatisfactory secondary (clostridial) fermentations dominated by undesirable end products, such as ammonia and butyric acid, that are poorly consumed by livestock.