Is corn silage a forage? Of course the answer is yes and no. About ½ of the corn plant is grain and about ½ is forage making corn silage a unique “forage”. The corn plant is highly productive so yields of dry matter are greater than about any other forage, about 2 times alfalfa. In the distant past, corn silage was commonly used as a forage for cattle because of the large yield of nutrients per acre. The wet silage also added moisture to otherwise dry feedyard rations. With the advent of the ethanol industry, most cattle in Nebraska feedyards are fed wet byproducts like distillers grains or gluten feed. Therefore, the moisture from corn silage was not needed and the distillers grains provided more protein than needed. Cattle feeders then replaced silage and alfalfa with inexpensive baled cornstalks.
About 6 years ago we realized we were harvesting high moisture corn which was stored in a silo and then baling the residue after it dried. It seemed logical to just harvest the two together as corn silage. That logic lead to 5 years of intensive research on corn silage.
Some of the research has been directed to the use of corn silage as a substitute for corn grain in finishing diets for feedyard cattle. This type of research had been conducted 40 years ago. The difference today is the availability of distillers grains. We conclude that corn silage can replace 30 to 45% of the corn grain in finishing rations when 25 to 40% distillers grains are fed. Feed efficiency declines some as the silage level increases, but that is offset by the lower cost of the silage.
The other important use of corn silage is as a primary energy source for growing (backgrounding) calves or for beef cows. (Clearly corn silage has good value for dairy cows but I will leave that for more qualified experts to discuss). Again in the distant past we fed rations of 90% corn silage and 10% soybean meal to growing calves and they gained 1.8 to 2 lb/day. When distillers grains became readily available, we fed 15-30% distillers grains and 80 to 85% corn silage, and the calves gained 3 lb/day. That caused us to take a closer look at the protein in the corn silage. We found that there was much less “bypass” protein in the silage than we had believed previously. The distillers grains are an excellent source of “bypass” protein and complement the corn silage very well.
The economics of silage use are a bit complicated. We have market prices for corn, alfalfa and grass hay reported routinely. That is not the case for corn silage. Typically corn silage is priced based on corn grain price because the alternative for a farmer is to just harvest the crop for grain. Therefore, we choose to price silage based on the price of corn grain in the field. Corn price typically increases from harvest to the following summer and the increase is roughly equivalent to storage cost. So the value of corn grain in the field is equal to fall price minus harvest costs.
If the cash price for corn in October is $2.86/bu, then the value in the field is $2.39/bu and silage is about $20.44/ton at 38% dry matter. Silage harvest removes more plant nutrients than accounted for in the grain. However, if manure produced from feeding the silage is applied to the field then the net is a value of $3.54/ton giving the silage in the field a price of $16.90. The cost to the cattle producers for harvest, storage and manure spreading is $15.83/ton for a price at the silo of $32.73. With a 10% shrink in the silo, the silage ready to be fed would be $36.37/ton. Obviously the shrink and manure credit are very important to the economics.
One method for comparing values of forages is to calculate the cost per unit of energy, in this case I am using TDN. Using the prices listed above, silage would cost $0.0665/lb of TDN. Corn grain would be $0.0790 and distillers grains would be $0.0607. Hay at $70/ton would be $0.084. These estimates suggest corn silage, especially when fed with distillers grains, can be a very economical forage.
The use of corn silage for feedyard cattle, backgrounded cattle and cows was thoroughly discussed at a conference on June 17, 2016. The information can be accessed at http://beef.unl.edu/silage-beef-cattle-conference