The changes in behavior associated with a (subclinical) acute and a chronic health challenge were investigated to assess their potential value for the development of an early disease detection system in beef cattle. The hypothesis was that acute challenges would lead to acute but transient changes in behavior, whereas the converse would be the case during chronic challenges, with changes taking longer to develop, but being more persistent. For this purpose, Holstein-Friesian beef bulls were challenged either with a repeated lipopolysaccharide (LPS) intravenous bolus given at 3 increasing doses over the course of 5 d, or with a single dose of the abomasal parasite Ostertagia ostertagi, acting as models of acute and chronic challenge respectively. A third unchallenged group acted as controls. Fecal and blood samples were taken regularly and analyzed for fecal egg counts (FEC), pepsinogen concentration and LPS antibodies. A sensor was fitted to the front leg of each bull to record activity and posture. Video recordings were taken to monitor drinking and feeding behavior. Antibodies to LPS were detected only after the third LPS challenge. Fecal egg counts were detected 3 wk post infection, and pepsinogen increased roughly at the same time in parasitized bulls. Body weight of parasitized animals was reduced relative to controls after 17 d post infection (P < 0.001), whereas there was no difference in performance between the LPS and control animals (P > 0.05). Effects of LPS on behavior lasted only for a few hours, presenting themselves as reduction in activity approximately 10 h after the first challenge (P = 0.057). The clearest behavioral changes due to parasitism were on posture. Parasitized animals had less frequent (P = 0.003), but longer lying episodes (P = 0.038) than controls. Once established, these changes persisted for 30 d post infection. However, there was no treatment effect on overall activity, measured by the number of steps taken or on total lying time (P > 0.05). Frequency of feeding and drinking episodes and their duration were not affected by health challenge (P > 0.05); however there was an increase in average duration of feeding (P = 0.013) for the parasitized animals. Even though the parasite challenge had significant effects on several aspects of behavior, these may be considered too subtle to be useful indicators of disease; however when used with other measurements, they may prove helpful for the early detection of disease in beef cattle.