Summertime Silage Feeding Problems

Warmer weather can bring a whole new set of issues related to silage quality and feeding value, which affect dry matter intake by high producing cows. During warmer weather, the tendency for growth of any yeast and bacteria present on the plants before ensiling increases greatly compared to their growth in cooler weather. Silo management or feeding may need to be altered to minimize these problems.

Yeasts are normally present on plants as they grow in the field. These multiply to some extent while crops are wilting in the windrow in the case of haylage or after chopping and before air exclusion in the silo for any silage. Limiting the growth of these unwanted species of single-celled organisms is one of the reasons we stress packing silage quickly and completely. Getting oxygen out of the silage is the key, yeasts do not grow in low-oxygen environments. Regardless of the weather, once oxygen is added back to the silage, these organisms or their spores begin to grow again. However their growth is expedited by warmer temperatures. When the temperature exceeds 50 to 60 0F, and especially when temperatures exceed 80 to 90 0F, yeasts grow exponentially, and the consequences of their growth become more important. Obviously, the population density of the yeasts or spores also will help determine the initial rate at which they begin to grow.

The heating that we feel in the silo or in the feed bunk is primarily a result of yeast growth. The heat is given off when these organisms use sugar or starch in the plant material for their growth. Unfortunately, these nutrients are part of the feed energy that we would like rumen bacteria to convert into energy the cow can use for milk production or growth.

Therefore, yeast growth causes energy loss in silage. In addition, part of the soluble protein in silage is used during yeast growth and lost prior to feeding, which reduces the protein available for rumen bacteria. As an added insult, 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. Unwanted yeast growth produces more yeast cells, which accelerates nutrient losses, heating, and production of ammonia. Finally, feeding silage in a TMR can make the problem worse in hot weather because silage yeasts get a fresh supply of oxygen and grains (containing soluble starch and proteins) once the TMR is mixed.

Check your silo frequently to see if whether the amount being fed each day is enough to minimize the problem in the silo. If the heating is considerable, use more silage each day if at all possible and perhaps pay more attention to keeping a clean bunk face on bunker silos. If the TMR is heating greatly within a few hours of feeding, you may need to feed less at a time and mix and feed TMR more often (perhaps going from 1 to 2 feedings per day or from 2 to 3 feedings per day) for a time period. Another method may be to offer more feed at night, when the temperatures are cooler, to encourage cows to eat more. Also, there are TMR and silage additives that retard the growth of yeasts and molds as their principle objective, and these may be cost effective if they minimize loss of dry matter intake by your lactating cows. 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 2, 4, and 8 hours after feeding.

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Jud Heinrichs

Dairy and Animal Science Extension