The addition of fatty acid (FA) supplements and oilseeds are a common practice in the dairy industry to increase yields of fluid milk and milk components. FA supplements contain >85% total FA while oilseeds are closer to 15-20% FA. While both contain differing amounts of individual FA, the level of oleic acid (cis-9 C18:1) within these fat sources are vastly different. Previously, supplementation of cis-9 C18:1 to dairy cows has been found to increase nutrient digestibility and body weight reserves. Additionally, varying amounts of cis-9 C18:1 can impact production responses differently depending on production level of the cow. In order to explore the impacts of cis-9 C18:1, the inclusion of FA supplements and oilseeds containing cis-9 C18:1 were evaluated to improve cow performance and efficiency. The first two experiments used FA supplements containing different amounts of cis-9 C18:1. First, the effectiveness of a cis-9 C18:1-enriched Ca-salt was assessed to increase flow of cis-9 C18:1 past the rumen and second, FA supplements were evaluated to test if the FA profile is more important than the form of a supplement. Results showed that a small dose of a cis-9 C18:1-enriched Ca-salt can be an effective tool to increase flow of cis-9 C18:1 to the small intestine and the FA profile of the supplement is more critical than the form. Next, we determined doses of oilseeds varying in cis-9 C18:1 level on cow performance. Whole cottonseed can increase nutrient digestibility and milk production up to 16% dry matter inclusion, whereas a high cis-9 C18:1 soybean had continued positive production effects from 0 -24% DM inclusion. Additionally, heat-treatment impacted ground high cis-9 C18:1 soybeans, as roasting improved milk production responses compared with raw.
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