Soybeans and dairy cows have walked hand-in-hand pretty well since the inception of total mixed rations (TMR) in the dairy industry. Known primarily for their high-quality protein suppling the nearly ideal amino acid profile, these oilseeds also provide fat for energy to support lactation. When soybeans are fed, nutritionists anticipate a bump in productivity but have learned to walk the line to not overfeed them. Overfeeding conventional soybeans can be harsh on the rumen due to the high percentage of linoleic acid, resulting in milkfat depression.
Decades of research has illuminated the details of maximizing the soybean benefit in the dairy ration, such as ideal inclusion rates and roasting. Recent developments in soybean breeding have developed a variety with the promise of higher inclusion rates due to an elevated proportion of oleic acid, which is easier on the rumen and may provide important benefits to the cow as well. A greater inclusion rate in the ration could support the herd during times of high production.
The industry recently started feeding high oleic soybeans, and questions began to emerge. How much can be fed? Should they be fed raw or roasted? Does this replace other feeds in the diet? A team of researchers in Adam Lock’s lab at Michigan State University got to work with a series of projects to answer these industry-led questions.
The high oleic effect
Conventional soybeans hover around 18% to 20% fat, of which about half is typically linoleic. “The high oleic soybeans we were studying contained around 75% to 80% oleic acid,” explained Lock, a professor at Michigan State University, on the October episode of the “Dairy Science Digest” podcast.
The fatty acid profile of conventional soybeans of around 50% linoleic acid is similar to the fatty acid profile of corn and cottonseed oil. Recent research has shown oleic acid to be healthier for human consumption, so a market is beginning to emerge. Preliminary results have also shown a positive response when it is fed to dairy cows, so forward-thinking producers with an existing soybean land base capitalized on the opportunity with greater plantings in many states this crop year.
Two research projects recently published in the Journal of Dairy Science were designed to answer three questions around these soybeans:
1. What is the ideal rate to feed high oleic soybeans to mid-lactation cows?
2. Should these soybeans be fed raw or roasted?
3. Does feeding additional rumen undegradable protein (RUP), also known as bypass protein, help when soybeans are fed raw?
The initial trial compared inclusion levels ranging from 0% to 24% high oleic soybeans in the TMR. The Michigan State research team employed 36 mid-lactation cows to determine the ideal way to feed high oleic soybeans. When compared to the control, which was a ration with conventional soybean meal, the cows fed high oleic soybeans averaged 6.6 more pounds of energy-corrected milk (ECM) per cow per day. Results suggested a sweet spot of between 8% and 16% diet dry matter inclusion to maximize the response.
Raw versus roasted
Roasting soybean meal was initially studied in the 1990s and determined to protect the protein profile of the beans from rapid degradation in the rumen, thus allowing the amino acids to be absorbed and used by the cow, resulting in a bump milk yield. Lock’s team wondered how ECM would be affected when the high oleic soybeans were roasted.
When 16% roasted high oleic soybeans were fed in lieu of conventional soybean meal, ECM rose 10 pounds per cow per day. Raw high oleic soybeans boosted ECM more modestly, at 3.5 pounds per cow per day, and when RUP was added, that jumped to 5.3 pounds per cow per day compared to conventional soybean meal.
Roasting clearly benefits the mid-lactation cow. “Consistency is key,” Lock advised on how to utilize this practice. “On-farm roasting variations need to be managed. Work with your nutritionist to ensure metrics are met for ideal roasting conditions.”
If roasting is simply not available to your farm, consider adding supplemental RUP to get an extra bump in production. These improvements in ECM came with only a 2-pound climb in dry matter intake.
“Oleic acid has been shown to improve fatty acid absorption and insulin sensitivity and limit fat mobilization,” explained Lock. “The metabolism and digestion seem to be improved.”
Future research
While research answers the immediate question at hand, it often generates more questions. Still, there are questions about the most cost-effective feeding rate for high oleic soybeans. How do they impact digestion? Would the shift in insulin sensitivity help the transition cow retain body condition? How would lactating cows respond when we add precursors for milkfat to the high oleic diet, such as acetate and butyrate? What role does palmitic acid have in improving production? All these and more are “on the list” for future research efforts of Lock’s lab.
To learn more about high oleic soybeans, listen in to the monthly podcast, “Dairy Science Digest” on your favorite podcast platform. The research findings were summarized in a peer-reviewed open access Journal of Dairy Science article found at www.journalofdairyscience.org.
