When it comes to putting up alfalfa hay, you want to capture plants at peak nutritional value. However, weather can be a problem. Sometimes, hay will get rained on before it can be baled and producers will use a propionic acid preservative. But new research from the University of Wisconsin Marshfield Agricultural Research Station shows that propionic acid may have limited value.

Based on the observations of 42 treated round bales over a two-year period, researchers say the potential to improve nutritive value relative to the cost of treatment is not especially favorable.

“Past studies have demonstrated clear benefits from application of propionic acid-based preservatives during packaging of small square bales of alfalfa hay,” the researchers said. “However, results obtained from this study with large round bales were much less favorable. This could be related to the greater size of the bales packages, differences in application methodologies between round and square (plunger-type) balers, or other factors,” they say in an article printed in the January 2012 Journal of Dairy Science.