Summer Heat is Silage Enemy

Warmer weather brings a new set of challenges to maintaining silage quality and feeding value, which affects high-producing cows’ dry-matter intake, a North Dakota State University dairy expert warns.

Warmer weather tends to greatly increase the growth of any yeast and bacteria that were on the plants before ensiling, says NDSU Extension Service dairy specialist J.W. Schroeder. Producers may need to alter their bunker or silo management to minimize the loss of forage and feed, especially during drought-related forage shortages and when fuel costs hit unprecedented highs, as they have this year.

Yeasts normally are on plants as they grow in the field. The yeasts multiply to some extent while crops that will become haylage are wilting in the windrow, or on crops for silage after they’ve been chopped and before air exclusion in the silo.

“Limiting the growth of these unwanted species of single-celled organisms is one of the reasons for stressing the importance of packing silage quickly and completely,” Schroeder says. “Getting oxygen out of the silage is the key, since yeasts do not grow in low-oxygen environments.”

Regardless of the weather, once oxygen is added back into the silage, these organisms or their spores begin to grow again. However, warmer temperatures expedite their growth. When the temperature exceeds 50 to 60 F, and especially when it is above 80 to 90 F, yeasts grow exponentially, and the consequences of their growth become more important.

The heat felt in the silo or feed bunk primarily is a result of yeast growth, which uses sugar or starch in the plant material. However, the sugar and starch are part of the feed energy cows need for milk production or growth.

In addition, yeast growth uses part of the soluble protein in silage, which reduces the protein available for milk production. Plus, when yeasts break down protein, they produce ammonia.

“Unfortunately, both heated silage and the smell of ammonia strongly reduce the palatability and resulting intake of silage by the dairy cow,” Schroeder says.

The unwanted yeast growth also produces more yeast cells, which increases nutrient losses, heating and ammonia production.

Schroeder cautions that producers may make the situation worse by feeding silage in a total mixed ration (TMR) in hot weather. That’s because silage yeasts get a fresh supply of oxygen and grains containing soluble starch and proteins once the TMR is mixed.

He has this advice on how to preserve feed quality:

“Whatever management changes you choose to use, check to be sure your approach is working by regularly monitoring dry-matter intakes and feed-bunk temperatures at two, four and eight hours after feeding,” Schroeder says.

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Source: J.W. Schroeder, (701) 231-7663, jschroed@ndsuext.nodak.edu
Editor: Ellen Crawford, (701) 231-5391, ellen.crawford@ndsu.edu