Fatigued pig syndrome is a swine industry problem. The objective of this study was to evaluate increasing dietary vitamin B3 dose effects on delaying muscle fatigue onset. Barrows were assigned one of five B3 doses in a swine finishing diet. After 10 d of supplementation, barrows were subjected to a performance test until fatigued. Intake decreased in pigs fed greatest B3 dose. Pigs supplemented greatest dose through drench solution run time and run duration increased during the performance test. Supplemented barrows had decreased creatine kinase and lactate blood concentrations compared to un-supplemented barrows pre- and post-fatigue. There were no treatment differences for gait mat analyses; however, there were changes between pre- and post- fatigue for velocity, stride time, cycle time, cadence, and cycle length. While not significant, data appears to indicate vitamin B3 may be a countermeasure to fatigue with potential for greater improvements through increased supplementation period.