Feeding Roasted Soybeans to Dairy Cattle

Dr. Maurice Eastridge, Professor and Extension Dairy Specialist, Department of Animal Sciences, The Ohio State University

With summer approaching on the calendar, and even recent temperatures causing it to feel like summer is already here, leads to the excitement for grilling outdoors and roasting over a campfire. Those associated smells and flavors get the salivary glands to work. Interest in roasting home-grown soybeans has recently increased again with the availability of high-oleic soybeans (Plenish Soybeans, Pioneer). We have known for many years that heat treatment of some plant protein sources increases rumen undegradable protein (RUP) which can be advantageous for increasing milk and/or milk protein yields. However, overheating such feed ingredients can reduce protein digestibility. Also, the heating inactivates enzymes that can cause oxidation of fatty acids leading to rancidity and inactivate trypsin inhibitor that can cause a reduction in protein digestibility.

When soybeans are processed for removing the oil, the oil is removed either by solvent extraction or extrusion (or expelling). The hulls are removed from the seed before solvent extraction and can be used as a livestock feed or added back to the soybean meal. If the hulls are left separate, the soybean meal typically contains 48% crude protein (CP), but if they are mixed with the soybean meal, the protein level in the soybean meal is typically 44%.  These protein levels are expressed on an as-fed basis. Whole soybeans typically contain about 36 to 38% CP (as-fed basis), whether they are either conventional or high-oleic soybeans. Both types of soybeans typically have similar levels of fat at about 20% (DM basis; 18% as-fed basis). However, the conventional soybeans are high in linoleic acid (C18:2, a polyunsaturated fatty acid) and the Plenish soybeans are high in oleic acid (C18:1, a monounsaturated fatty acid). Polyunsaturated fatty acids are more likely to disrupt ruminal fermentation in dairy cows which may cause a decrease in feed intake, fiber digestibility, milk yield and/or milk fat concentration and yield. With the current pricing of milk, the price of milk fat ($3.33/lb) is the pace setter for revenue.

Based on the Ohio State crop enterprise budgets, the current cost of production for soybeans is about $11.50/bu (60 bu/acre yield), the USDA forecast for average farm price for soybeans during 2024/2025 is $11.20/bu, and the cost of roasting soybeans is typically $35 to 45/ton (~$1.20/bu). Based on the current feed prices as reported in this issue of Buckeye Dairy News, whole roasted soybeans have an actual price of $454/ton ($13.62/bu) and the predicted value is $352/ton ($10.56/bu). Thus, they are overpriced at this time in respect to some other feed ingredients; however, if you grow your own soybeans and add the cost of roasting, the price at $12.70/bu is more favorable than the purchasing of roasted soybeans at $13.62/bu. Even though these prices are for conventional soybeans, these price trends can be used in context for high oleic soybeans. One must keep in mind that the price for Plenish soybeans is at a premium since they are primarily grown for human food ingredients (e.g. the high oleic oil), and when considered for livestock, they are preferred over conventional soybeans.  Some considerations for use of roasting soybeans include:

  1. The temperature for roasting should be 290 to 315oF (desirable temperature varies based on type of equipment and duration of the heating process). Then the soybeans need to be steeped for 30 minutes or longer (few hours), with the duration of steeping depending on roasting temperature and storage container after roasting (i.e., ability to maintain heat). Steeping is especially important if roasting occurs at the lower temperatures and with limited holding times within the roaster. After the roasting and steeping, the soybeans need to be cooled. This can be done by pushing or pulling air through the beans. For example, if a gravity flow wagon or other rather small on-farm containment is used, an aerator should be placed in the beans at the end of the steeping time. Soybeans heated at too high of temperature or steeped too long can have reduced protein digestibility. Some laboratory tests are available as indicators of underheating or overheating of soybeans, and these can be useful in monitoring processing methods, but they my not reflect what actually happens within the animal because of impacts of the ruminal fermentation and rate of digesta passage.
  2. During the roasting process, there will be some shrink. This is primarily due to loss of some moisture, hulls, and pod trash.
  3. After roasting, the soybeans can be fed as ground or cracked soybeans. Earlier Ohio State research found that the soybeans fed in quarters or eights improved digestibility in comparison to feeding whole soybeans without reducing the RUP levels in the soybeans as observed with feeding them ground.
  4. Inclusion level in diets for lactating dairy cows ranges from 10 to 20%, depending on other ingredients in diets, production levels in the cows, and target levels of protein and unsaturated fat.


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