Quality silage

Jersey cattle eating silage in a freestall barn with headlocks.

Jersey cattle eating silage in a freestall barn with headlocks. Photo by Lyssa Seefeldt.

Quality feed is very important for production of milk on a farm.  Cows are fed a total mixed ration (TMR) that is balanced according to the nutritional needs of the animal.  Energy in the diet is especially important for dairy cattle for daily production of milk, support of digestive health, and for effective utilization of other nutrients in the diet.  Dairy farms often utilize agricultural by-products to supplement nutrients in the cow’s diets.  Examples include corn bran syrup, a by-product from ethanol production, and whey permeate, a cheese production by-product can be used as energy sources.  Most farms meet their forage needs by growing alfalfa and corn for silage.

The science behind making high quality silage for a dairy diet is a two-step process.  First, there is an aerobic phase where bacteria that utilize oxygen and some of the carbohydrates from the plant material multiply, producing carbon dioxide and water.  Neither of these products helps to preserve the harvested forage, so reducing the length of this phase is desirable.  This is the reason why forage is chopped into small pieces so that it can be more readily packed together, reducing the amount of oxygen present in the forage to be preserved.  This phase is the reason you see farmers continuing to chop forage through all hours of the day and night, as the oxygen-loving bacteria start this process as soon as the plant material is cut.  Packing down the forage also helps force oxygen out of the plant material.  After packing is complete, plastic coverings are weighted down, often with tires, and placed on top of the forage to seal out additional oxygen.

Once the aerobic bacteria use up the available oxygen in the chopped forage, they die, allowing anaerobic bacteria that do not need oxygen to multiply and ferment or pickle the forage.  These bacteria produce organic acids such as lactic acid that increases the acidity of the forage, reducing the pH.  The pH of the forage is reduced to a point where no further microbial growth can occur, preserving the forage as long as oxygen is kept from entering the fermented forage.  This is the same type of fermentation process that is used to make sauerkraut.

Many farms have went from vertical storage in silos to horizontal storage in bunks or silage bags.  The harvested feed is packed and covered with a thick plastic to help reduce any chances for spoilage to occur. This is a critical part of sealing the feed off from the outside environment which would expose the feed to oxygen again, preventing preservation of the feed.  To help promote the fermentation process, often small amounts of lactic acid producing bacteria are added to the forage as it is harvested.

Keeping feed fresh once it has started to be fed is just as important as the initial preservation.  In horizontal feed storage, the feed is removed from the piles using a machine called a facer.  A smooth face, or edge on the silage, reduces the area of oxygen penetration into the pile, allowing the feed to stay fresh longer.   Once a silage bag has been opened or the plastic has been pulled back on a silage pile, it is important to keep using the silage nearest the opening as oxygen is allowing aerobic bacteria to recolonize on the feed, breaking it down while producing water and carbon dioxide, just like at the beginning of the fermentation process.  This lowers the feed quality and causes spoilage.


Note: This article originally was published in the Marquette County Tribune, Waushara Argus, and/or the Berlin Journal.  This article was written by Lyssa Seefeldt, UW-Extension Agriculture Agent for Marquette County unless otherwise noted.