A hard frost and continuing cold temperatures have J.W. Schroeder worried that silage corn won’t be able to ferment adequately in North Dakota.

What’s needed, says the North Dakota State University extension dairy specialist, is warm weather. “If that happens, I wouldn’t worry; the corn will ensile. But, given the size of most drive-over silage piles, that seems doubtful.”

Packed, cold silage piles are well-insulated, Schroeder says, and if there’s only a short warm spell, probably only the outer layers of piles will ferment. Inoculants may not help ensile either, because they need some heat to activate. Inoculants will kill undesirable “bugs,” or microbes, and yeast, however.

“Without adequate fermentation, this refrigerated pile of feed will keep just fine until temperatures rise,” he says. When they do, silage will begin to heat in the feed bunk, as well as spoil in the storage bunker. Silage that hasn’t completed ensiling will spoil faster than fermented crop as it’s exposed to air. So Schroeder recommends making sure piles are monitored often and closely for changes in temperature, appearance and smell. Adjust rate of feed-out to reduce exposure to air.

“If the pile can sit for three to four weeks before feeding, it could have time to attempt to ensile. If you open the silo or pile in about a month and it still looks and smells like green chop, then little has happened.”

Schroeder suggests two ways to check fermentation. One is to probe piles for temperature changes; the other is to check the pH.

Silage at about 100-110 degrees F is going through normal fermentation. Temperatures lower than that show the silage is too cold to ferment; silage at 120-130 degrees is probably spoiling.

Normal silage should have a pH of about 3.6-3.8. If the pH is more than 5, not much fermentation has happened. If the silage still smells normal, it is fine to feed but should be treated as though it were fresh green chop.

If you are feeding large amounts of a properly fermented silage, which typically has a dry matter content containing 1-2% sugar, don’t make a sudden switch to unfermented silage that has 6-8% sugar. Take a week to adapt your cows to this silage; feeding large amounts overnight could contribute to an overload in a cow’s rumen and cause her to go off feed, he warns.

Need to feed new silage immediately? You may want to adjust your ration, because new silage won’t yield as much milk as silage that has fermented 60, 90 or, even better, 120 days.