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Combat Summer Heat and Preserve Nutritional Quality of Total Mixed Rations

Summer heat and humidity provide several challenges for dairy producers. One important challenge often overlooked is heating of the dairy ration. Dairy cattle rations, even when sitting in the bunk for just a few hours, may experience secondary fermentation due to continued bacterial growth because of high heat. Secondary fermentation causes a reduction of feed quality, generates undesirable odors and may result in reduced intake. To help restrict secondary fermentation, control growth of undesirable microbes, keep rations cooler, and maintain feed quality, producers often add mold and wild yeast inhibition products to the total mixed ration (TMR).


What causes the ration to heat? Blending different feed ingredients in a TMR allows microbes access to additional nutrients along with fresh air (oxygen). This process, along with a hot feed bunk and higher humidity, creates the perfect growing conditions for molds and wild yeast to rapidly grow. The fermentation of the feed generates heat and in return, increases the temperature of the TMR. It’s also possible a dairy is adding more moisture to the ration by adding green chop forages or seasonal wet by-products which are not ensiled. The moisture content of the TMR may also increase as water from the cow cooling sprinklers drifts onto the feed.

Measuring temperatures of the TMR and taking readings throughout the day is a great way to monitor secondary fermentation. Producers are often surprised to learn how quickly the TMR heats up. In just a few hours, wild yeast and mold counts grow exponentially. Feed samples, sent to a lab for analysis, may not represent the extreme situation of your cow’s experience. Your best indication of a problem is to monitor the TMR temperature and watch how the cows eat their ration. When the cows back off, feed quality may be the issue.

The quality of a TMR can go out of condition quickly in summer conditions. Preventing a secondary fermentation and its accompanying heat spike is so important and it’s especially true if the forage or feed quality is already marginal.

Below are a few feed management practices to keep feed fresh during summer months:

  • Feed twice per day. If possible, provide fresh feed when conditions are relatively cool. Consider offering two-thirds of the TMR in the late afternoon/early evening and one-third in the morning.
  • Push-up feed frequently.
  • Carefully manage the face of your upright silo, bag or bunker. Removing 12 inches a day is recommended and it is best to remove from the entire face.
  • Use preservative products such as Silage SAVOR® at the time of harvest.
  • Always use a thermometer to check temperatures. Feeling the temperature of the feed with your hand will not give you accurate results.
  • Use highly concentrated, buffered broad-spectrum mold inhibitors such as Feed CURB® or Myco CURB®. Buffering the blended organic acids makes them less corrosive and much safer to handle.

If wild yeast is a problem, adding Feed CURB at one kilogram per ton of mixed feed will be highly effective at controlling secondary fermentation and heating of the TMR. Single acid treatments often fail to control a wide variety of molds or wild yeast. For example, propionic acid will control some molds but is completely ineffective on others and only “irritates” yeast. A mold inhibitor with a higher total acid content which contains acetic acid has demonstrated efficacy in controlling yeast growth. Acetic acid is highly effective at controlling yeast. Studies have shown combining different organic acids will provide greater inhibition of many molds and yeast.

Summer weather is unpredictable. When labor is limited, feed quality is not optimum, and conditions dictate incorporating a premium mold inhibitor into the TMR can help to protect your investment. For your forage preservation needs, trust Kemin Animal Nutrition & Health to provide products, people and service to maintain the nutritional value and integrity of your feed.

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