Kung: Aerobic Deterioration of Silages – Causes, Results & Impact on Ruminants
Posted on December 4, 2012 in Forage Foundations
Forage cannot be made better from the point it leaves the field, therefore our goal as an industry is to start with the best quality forage possible and preserve it with excellent silage management, said Dr. Limin Kung, University of Delaware.
Harvesters and producers should have two goals in making fermented feeds. At the front end of silage production, you want fermentation to occur right away when it is most active. At the backend, you want to make sure the feed is stored properly so the investment is taken care of until feedout occurs.
In most cases, you can expect a nutrient loss of 9 to 15 percent when you ensile something. That can be as high as 20 to 40 percent, depending on management.
“You are losing net farm income with the more losses you have out of your silo,” Kung said. “Nobody can get you to zero, but we can get you closer to zero.”
As mentioned earlier, the goal is for fermentation to occur as quickly as possible. The faster it gets done, the more nutrients are saved. Then, if you continue to keep air out of the system, it remains stable.
“Air is the worst enemy of silage at the start and at the end,” Kung said. “Air at start can delay fermentation and allows for growth of undesirable bugs.
“If you chop it, you better pack it,” he said. Just sitting in a wagon for six to eight hours will cause massive losses.
Exposure to air during storage causes excessive heating. In big masses, the heat begins to accumulate.
Most people believe molds are the microorganisms that initiate aerobic deterioration because that is what they can see. Kung corrected that actually yeasts are to blame.
There are good yeasts and bad yeasts, he said. Three different types of yeasts are found on plants. Lactate assimilators are the worst because their population is dependent on air, sugar and inhabilitory factors. They are very tolerant of low pH conditions, and can therefore withstand forage storage conditions.
The keys to preventing lactate-assimilating yeasts from taking over the silage is to prevent the feed from being exposed to air or to try to minimize the number of those yeasts in the silage. With fewer yeasts, it is easier to stay ahead of the spoilage.
Yeast is problem in high moisture corn, corn silage and alfalfa, respectively. Growth is affected by warm ambient temperatures, time of exposure to air, porosity of the material and the chemical compound.
“Anytime you see mold, the answer is air,” Kung said.
Signs of spoiled silage include seeing temperatures higher than 100 to 105°F after the silage is cured, reheating in the feed bunk, lack of sharp acid or sweet smell, musty, moldy smell, and visible mold.
Spoiled silage can lead to decreased intake and the production of mycotoxins, both of which affect the dairy producer’s bottom line.
A study at Kansas State University involving steers showed that when they were fed spoiled silage at 0, 5, 10 and 15 percent of the ration, the steers ate less and what they did eat was less digestible.
How to stop spoilage
At the front end, homolactic acid-based silage inoculants can enhance the speed of fermentation. Their performance is variable, though. Kung said about one-third of the time they’ve been found to improve stability, one-third of the time they have no effect, and one-third of the time they can make it worse.
L. buchneri has been found to improve crop stability. The benefits from that improved stability far outweigh any dry matter loss that occurs from its use, Kung said. Buchneri is naturally occurring on plants, but many times it is not the right strain or there isn’t as much of it as needed.
At the back end of silage production, an oxygen barrier cover can help keep the air out, especially for forages you’re going to keep a long time, he said. Reusable tarps and good weights are useful in keeping the plastic down tight to the forage. Routine management to patch holes in plastic must be adopted if it is not already commonplace.
Managing the face of the bunker is another important step. When it is hot, dry and poorly packed, you have to keep the face clean and feed out at a higher rate to keep it fresh, Kung said. Remember to keep the face away from afternoon sun and keep plastic on the leading edge to prevent air from entering under plastic.
Forage storage and management