ARS | Publication request: The effect of harvest moisture and bale wrapping on forage quality, temperature, and mold in orchardgrass hay

Submitted to: Journal of Equine Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 30, 2011
Publication Date: November 28, 2011
Citation: Martinson, K., Coblentz, W.K., Sheaffer, C. 2011. The effect of harvest moisture and bale wrapping on forage quality, temperature, and mold in orchardgrass hay. Journal of Equine Veterinary Science. 31:711-716.

Interpretive Summary: For equine applications, producing mold-free, well-preserved hay is critically important. Hays packaged in large packages (round or square bales) are more prone to mold and heat spontaneously than small (100-lb) bales that must be handled manually. In this study, maintaining forage quality and reducing mold growth was achieved by either baling dry (124 g/kg) orchardgrass hay, or by wrapping bales in stretch plastic film, regardless of initial moisture. The currently recommended moisture threshold for safe storage of alfalfa or mixed hays (150 g/kg) was an appropriate threshold for orchardgrass. This recommendation should be carefully followed; orchardgrass bales were prone to significant molding and forage quality losses at moisture concentrations slightly greater than 150 g/kg. This abrupt line between high-quality and damaged hay likely is one reason some horse owners assume it is difficult to feed quality round bales to horses. Wrapping higher-moisture orchardgrass round bales also was effective in maintaining forage quality. However, the stability of higher moisture bales after unwrapping, especially during the summer months or with intermittent feeding schedules, needs further investigation. This information will help horse owners and hay producers who sell to the horse market.

Technical Abstract: The effects of harvest moisture and bale wrapping on forage quality and mold formation in orchardgrass hay intended for equine feeding have not been investigated. The objectives of this study were to assess the effects of initial bale moisture and wrapping on temperature, forage quality, and mold formation in large round bales of orchardgrass hay. Forty 1.2 x 1.5-m round bales of mature orchardgrass hay were baled at three different moisture ranges: <166 g/kg; 180 to 232 g/kg; and 259 to 337 g/kg. Selected bales within each moisture range were individually wrapped in plastic, and temperature sensors were placed in each bale for up to 10 weeks. The lowest (P=0.01) maximum temperature and heating degree day accumulations were observed during 2009 when initial the bale moisture was 124 g/kg, or when hay was wrapped, regardless of initial moisture content. During 2009, all wrapped hays resulted in similar forage quality (P=0.14) and mold counts (P=0.94) compared to orchardgrass baled at 124 g/kg of moisture. During 2008, hay baled at 166 g/kg resulted in fiber (P=0.82) and mold (P=0.21) components that were similar to higher moisture bales. Mold counts for hay baled at 166 g/kg and 124 g/kg moisture were 24.8 x 106 and 2.7 x 104 cfu/g, respectively, demonstrating that large round bales are prone to molding at relatively low moisture concentrations. Maintaining forage quality and reducing mold growth was achieved by baling dry (124 g/kg moisture) hay, or by wrapping round bales of orchardgrass hay up to 337 g/kg of moisture.