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1808 PD: The feeder’s job: When it rains

Steve Mooney Published on 09 December 2008

A heavy rain or snow soaks the face of the bunker silo.Puddles grow at the base of the face, seeping into the silage. The dry matter of this silage no longer matches the number on your mix sheet.

What do you do?



Rain and snow can complicate the feeder’s job. Days of rain and inches of snow add weight to bunker silages but no nutrients. If the feeder doesn’t adjust to this dry matter change, water will displace the nutrients of the forage, and the final mix won’t be what it’s supposed to be. In this situation, the loss of fiber from forage is the primary concern. Without adequate fiber the ruminal fermentation is altered and the chances for acidosis, DA and laminitis increase.

Research presented at the National Dairy Science meetings in San Antonio, Texas, showed that even one day with a “hot” ration can cause problems that will affect the cow for the remainder of her lactation. The feeder’s job is to make sure the ration balanced by the nutritionist is the ration eaten by the cows.

When it rains, the feeder must determine the new dry matter of this wet silage and adjust the weight of the silage required in the mix. The feeder should scrape the face and mix, sample and test the wet silage. However, if the feeder takes the time and effort to do this, the process of feeding the herd may be slowed or even stopped. If the feeder doesn’t adjust to the wet silage, problems with cow health will occur. Each of these options has its lack of appeal.

What are the alternatives? The feeder could fudge on the fly, skipping the measurement for the new dry matter. The feeder could increase the silage weights by some predetermined percentage or could add the feed to the mixer by volume instead of weight. Both of these options are less time-consuming, less accurate and more risky. If either of these alternatives is used, the benefits and risks must be fully understood.

Another alternative is the reallocation of the wet silage. A reduction in ration fiber due to wetter silage can affect some groups of cows more than others. Transition cows are probably the most sensitive to this mistake, followed closely by high and first-lactation groups. These classes of cows are often fed at minimum fiber levels so a loss of fiber would be detrimental.


Other groups of animals such as heifers and low groups receive higher or excess fiber in their diets and may be less sensitive to a temporary fiber reduction. Maybe the wet silage should be allocated to these groups with the fudge factors, saving the unexposed forage for the more sensitive groups.

Ultimately, the answer may be preventing our silages from getting wet in the first place. A nutritionist at a meeting here commented that he has clients who leave the covering plastic long enough to cover half or two-thirds of the bunker face, which minimizes weather exposure, yet the feeder works under the plastic without complication. Another option is to cover the face when precipitation is expected. The heavy rains and snows that really change dry matter percent rarely arrive without warning. Having a tarp at the ready may be the solution.

Another form of prevention is making sure water flows away from the face and not toward it. Silos and their covering systems should be designed so water is directed away from and not allowed to soak into the silage. In the end, the rainy day feeding strategy should match the dairy’s attitude toward time and risk management. Each dairy is unique and the feeders, nutritionists and cows must be proactive and come to a consensus on the standard operating procedures for rain and snow. The final plan should allow for timely mixing but prevent health problems in the cows. PD

References omitted but are available upon request at
—Excerpts from The William H. Miner Agricultural Research Institute Farm Report, September 2007

Steve Mooney
Research Post Doc
The William H. Miner Agricultural Research Institute