Feeding high oleic soybean to dairy cattle is the hot topic of the season based on the number of popular press headlines, research articles, and industry meetings that I have seen focus on it recently. It’s also on our minds at Miner Institute as we discuss feed costs and opportunities for producing more pounds of milk fat and protein. I recently heard Tom Overton share his thoughts about feeding high oleic soybeans in dairy diets at the Cornell Nutrition Conference. Here are some key points that I have taken away from his presentation as well as other meetings and discussions that I have been a part of:
High oleic soybeans offer the opportunity to feed more soybeans with less risk for milk fat issues. Soybeans are a commonly used oilseed in dairy cattle diets as they provide protein and energy in the form of fat to the cattle. However, feeding too much fat, especially polyunsaturated fatty acids like linoleic acid (C18:2), can have a negative effect on milk fat synthesis. Soybeans are a rich source of linoleic acid. Too much linoleic acid in the diet along with other factors that shift the ruminal biohydrogenation pathways used by the bacteria can result in more linoleic acid getting converted to the milk fat depressing trans-10, cis-12 conjugated linoleic acid (CLA) rather than the cis-9, trans-11 CLA. It only takes a few grams of trans-10, cis-12 CLA to reduce milk fat. Thus, nutritionists have limited commodity soybean use along with other oilseeds and supplemental fat sources to keep dietary Rumen Unsaturated Fatty Acid Load (RUFAL) values in range (typically <3.5% of dry matter). The high oleic soybeans have been developed to have higher oleic acid (C18:1; ~70-75 vs. 20-25%), less linoleic acid (~7-10% vs 50-55%), and less total polyunsaturated fatty acids than commodity soybeans. Thus, allowing the opportunity to feed more high oleic soybeans. At Purdue, Jackie Boerman’s group found no detrimental effects of feeding high oleic soybeans on milk yield with an increase in milk fat concentration, fat digestibility, and fat deposition compared to a control diet.
High oleic soybeans offer the opportunity to reduce feed cost or more importantly improve income over feed cost. Recently in the Journal of Dairy Science, Kevin Harvatine and his Penn State group evaluated the economic impact of use of 5% high oleic soybean in diets for dairy cattle. They calculated milk income less feed costs (MILFC) with the assumptions of increased milk fat production based on 5 previous studies and increased cost of a diet containing high oleic soybeans. The response was generally positive with a financial benefit ranging from $0.05 to $0.25/cow per day with a conservative milk fat response of 0.1 lb (45 g)/cow per day under various scenarios. Some studies have seen a much larger increase in milk fat. Interestingly, Tom Overton pointed out that using high oleic soybeans might be more of feed cost opportunity than milk fat opportunity since some of the studies suggested that one might only expect a milk fat response when there is some milk fat depression with elevated linoleic acid supply and availability before using high oleic soybeans. The feed cost saving is likely to come through less use of expensive fat supplements.
High oleic soybeans should be processed to improve the feeding value. Adam Lock and his group at Michigan State fed cows diets containing commodity soybean meal, raw high oleic soybean meal or roasted high oleic soybean meal and found that inclusion of high oleic soybean meal improved intake and yields of milk and milk components. Roasting the high oleic soybeans improved milk production responses compared with the raw soybeans. This isn’t surprising given the common practice of heat-treating commodity soybeans to increase the rumen undegradable protein (RUP) content as well as denature a trypsin inhibitor that could otherwise decrease protein digestibility in the small intestine. A challenge of effectively using high oleic soybeans is getting them processed on-farm as feed mills are not routinely sourcing and segregating high oleic soybeans.
Although there appears to be some benefit to using high oleic soybean in diets, Miner Institute is not planning to use them until we have extra crop acres to grow them or find a local source for them. Not surprisingly, growing and use of high oleic soybeans will be a farm-specific decision influenced greatly by geographical region and market factors.
— Heather Dann