Submitted to: Progressive Forage Grower
Publication Type: Popular Publication
Publication Acceptance Date: February 14, 2014
Publication Date: March 31, 2014
Citation: Coblentz, W.K. 2014. Preservation of hay with propionic acid. Progressive Forage Grower. 15(4):14-16. Technical Abstract: Most hay producers are quite familiar with the problems associated with baling moist hays. Normally, these problems include spontaneous heating, increased evidence of mold, losses of dry matter (DM) during storage, poorer nutritive value, and (in extreme cases) spontaneous combustion. Numerous factors influence spontaneous heating: i) bale moisture; ii) bale type and/or size; iii) bale density; iv) environmental factors, such as air movement or humidity; v) storage site; and vi) use of preservatives. Within a given bale type and/or size, the moisture concentration of the forage at baling is the most important factor affecting heating. However, large-hay packages are much more likely to achieve greater internal bale temperatures than traditional small (< 100-lb) rectangular bales. Generally, hay preservatives can be grouped into three general categories that include organic acids or their salts, ammonia-based products, and microbial additives. Of these, the most commonly used are various formulations of organic acids; normally, these formulations contain mostly propionic acid. Theoretically, these products work by inhibiting growth of aerobic microbes within the hay, thereby reducing microbial respiration, accumulation of heat, and limiting losses of DM and reductions in nutritive value. Historically, propionic-acid-based preservatives have worked (although sometimes inconsistently) with small rectangular (< 100-lb) bale packages. Recently, good results also have been documented for large-rectangular bales, but results for large-round bales have been disappointing. These discrepancies may be related to different application methods across bale types; however, other strategies of preservation, such as wrapping in plastic, may be preferred when using large-round bale packages.