Metabolic responses in animals during the intense physical activity have an intricate link to nutritional aspects. This study focused on examining the changes in blood metabolite concentration in Hararghe highland bulls during draught service, with the objective of evaluating their nutritional implications. Twelve intact bulls were randomly assigned to three groups of four animals each, with each group working for three draught hours (0, 4, or 6 hours). The Cobas Integra 400 Plus machine was used for the laboratory serum analyses. Data was analysed using a mixed model procedure with covariates in SAS-JMP-pro-17. The study results reveal that, except for phosphorus (P, mmol), the concentrations of glucose (GLU, mg/dL), total protein (TP, g/dL), blood urea nitrogen (BUN, mg/dL), and calcium (Ca, mmol) were significantly affected by their respective initial concentrations (IN¹) (p < 0.05), while dry matter intake (kg DMI/d) did not have an effect except on GLU and P (p < 0.05). Draught work hours did not influence GLU, TP, and BUN concentrations (p > 0.05), regardless of IN¹ and kg DMI/d, but did influence Ca and P. Therefore, it is important to monitor the level of Ca and P concentration in the blood of the bulls engaged in draught service to ensure their well-being.