Impacts of conventional and high-oleic soybean oil supplementation on rumen microbiology, physiology, immunity, and growth of recently weaned Brangus steers

Lay Summary High-oleic soybean oil (HOSBO) has a different fatty acid (FA) profile than conventional soybean oil (CSBO), which may lead to distinct effects on rumen microbiology, immune function, and growth when included in the diet of steers. Thus, the current experiment evaluated the effects of HOSBO, CSBO, and no oil supplementation on rumen microbiology, physiology, immunity, and growth of Brangus steers maintained in a forage-based system during the preconditioning phase. Although HOSBO and CSBO supplementation had minimal effects on rumen microbiology, it altered circulating FA profiles. The CSBO increased serum linoleic acid, whereas the HOSBO increased oleic acid. These differences in circulating FA were associated with distinct vaccine responses: steers receiving CSBO had stronger antibody responses to bovine viral diarrhea virus (BVDV), whereas those receiving HOSBO mounted stronger responses to bovine respiratory syncytial virus (BRSV). Growth also differed, with HOSBO-supplemented steers tending to be heavier than steers receiving CSBO by the end of the experiment. Overall, CSBO or HOSBO had minimal effects on rumen microbiology, but CSBO enhanced the immune response to BVDV, HOSBO enhanced the response to BRSV, and HOSBO promoted greater growth than CSBO.