Based on a presentation at the 2018 Silage for Beef Cattle Conference at the Eastern Nebraska Research and Extension Center
Forage quality is the Achilles’ heel for any ruminant nutritionist. The better the forage is coming out of storage, the better the nutritionist.
Undesirable micro-organisms include Salmonella, E coli O157:H7, other coliforms, Listeria, Clostridials, Cryptospordia, yeast and molds. Many of these organisms are normally found in the environment or may be transferred to crops when manure is applied before harvest. The key to minimizing their impact is managing the ensiling process such that they do not have the opportunity to proliferate or survive during fermentation or feed-out.
A practice often overlooked is discarding spoiled silage from feed. Dilution is not the solution to
pollution. A study to determine the effect of level of surface spoilage included in corn silage based on 16 diets was reported in 2000 (Whitlock et al.). The addition of spoiled silage decreased CP digestibility in a linear manner, and surface spoilage had large negative effects on DM intake and DM, OM and NDF digestibility. When the ruminal contents were evacuated, the spoiled silage had partially or totally destroyed the integrity of the forage mat in the rumen.
Improve Aerobic Stability
Aerobic stability of silage is defined as the length of time it takes for disturbed silage (exposed to air) to heat to 20°C. Aerobic stability is very important in maintaining nutrients and quality of silage during feed-out.
Many producers make the mistake of thinking feed is only in front of the cows for less than 24 hours — so aerobic stability should not make a big difference. Aerobic stability is the cumulative time from first exposure to air until consumed by the cow. If the face of a silo is not well managed, exposure to air and aerobic deterioration could begin days before the feed reaches the feedbunk.
Aerobic deterioration begins when silage is exposed to air and the temperature gets above 500°F (100°C). At this point, the wild yeast in the silage wake up. The result is more heat and higher pH. The conditions are now just right for mold and bacteria to wake up and further deteriorate the silage. At this point, changes start to become visible. By this time, most of the damage has already been done.
The high lactic acid and low pH produced in the fermentation phase do not protect silage against wild yeasts. Yeast can use lactic acid as a food source. Acetic acid, butyric acid and propionic acid are good yeast inhibitors. Butyric acid in silage does not play well with cows and should be avoided at all costs.
Rapid reduction in pH and aerobic stability at feed-out are the hallmarks of well-controlled silage fermentation and quality feed for the cows. Forage quality cannot be improved through the silage process. It can only be preserved or destroyed.
To download proceedings of the 2018 Silage for Beef Cattle Conference, or watch a video of the presentation, visit https://beef.unl.edu/2018-silage-beef-cattle-conference. The conference was sponsored by Lallemand Animal Nutrition, the University of Nebraska Extension and the Iowa Beef Center.