It’s no secret that forages play a key role in dairy rations. Coincidentally, one way to reduce the cost of a ration is to include more forage. But in order to do so, forage quality must be the primary focus. Emilie Branstad, graduate research assistant at Iowa State University (ISU), and Hugo Ramirez, assistant professor at ISU, address how to preserve silage quality and quantity in ISU Extension’s Iowa Dairy News
newsletter. “One must consider that a pile of forage is basically, ‘a pile of money,’” the authors suggest. A substantial amount of time, money, and effort is put into producing high-quality forage. No matter how forages are stored, the goal is to preserve these efforts. In bunker silos, drive-over piles, and similar storage methods, the top layer of forage is susceptible to oxygen exposure, which leads to dry matter and nutrient loss. “The money stored as fermented forage can essentially ‘evaporate’ into thin air,” the authors clarify. How do we keep our “money” from “evaporating?" In the fight to preserve silage quantity and quality, oxygen is enemy number one. The ideal environment for fermenting forages is one that is free of oxygen. To accomplish this, pack forage at a density of at least 15 pounds of dry matter per cubic foot. To protect the top 1 to 3 feet of stored forage, an oxygen barrier film is beneficial. Oxygen barrier film is a thin plastic sheet that is extremely resistant to oxygen penetration. “In other words, it’s a shield against oxygen,” the authors explain. The film is placed over the pile followed by the typical black and white plastic and weights such as tires. Why is another layer needed when the typical black and white plastic is thick and resistant? The authors explain that the thickness of the plastic or film does not determine its quality. Quality is based on the layer’s ability to resist the passage of oxygen. This trait is called oxygen transmission rate (OTR) and is measured in cubic centimeters of oxygen per meter of surface area over 24 hours. Black and white plastics have an OTR in the mid-hundreds to thousands, which is relatively high. Oxygen barriers are specially engineered to have OTRs in the single digits. “A black and white plastic is used for protection against the elements; oxygen barriers are used for protection on a molecular level,” the ISU researchers explain. They also emphasize that protecting the topmost layer of silage can result in significant economic savings. “We must consider that all the feed in the storage structure is pretty much paid for, so it makes sense to pay attention to protect our investment and ensure a high recovery of dry matter from the field to the bunker or pile,” the authors conclude.
Kassidy Buse is serving as the 2018 Hay & Forage Grower summer editorial intern. She is from Bridgewater, S.D., and recently graduated from Iowa State University with a degree in animal science. Buse will be attending the University of Nebraska-Lincoln to pursue a master’s degree in ruminant nutrition this fall.