Early and rapid detection of bovine tuberculosis (bTB) is critical to controlling the spread of this disease in cattle and other animals. In this study, we demonstrate the development of an immunoassay for the direct detection of the bovine bTB biomarker, lipomannan (LM) in serum using a waveguide-based optical biosensor. We apply an ultra-sensitive detection strategy developed by our team, termed lipoprotein capture, that exploits the pull-down of high-density lipoprotein (HDL) nanodiscs from cattle blood that allows for the recovery and detection of associated LM. We also profile the change in the expression of these TB biomarkers as a function of time from a small set of samples collected from studies of bovine TB-infected cattle. We demonstrate for the first time the direct detection of bovine LM in serum, and clearly show that the biomarker is expressed in detectable concentrations during the entire course of the infection.