White Landrace-Duroc cross pigs (n = 28, 14 male, 14 female; 81±16 d of age, 29±1 kg) were assigned at random to either sunlight exposure (SUN) in the spring and summer (n = 14) or confined to indoors as per standard practice (Control) with limited exposure to outdoor sunlight (n = 14). The study was replicated with a second group of white Yorkshire-Duroc-Landrace cross-bred pigs (n = 24, 10 male, 14 female) aged 80±13 d, 31.6±2.1 kg with sunlight exposure (SUN) in the summer and fall (n = 12) or Control (n = 12).From each group of pigs, a subsample of sun-exposed (n = 5 per group) and control (n = 4 per group) pigs, matched for body condition score, were selected for blood and tissue analysis; these analyses were performed only in a subsample due to cost constraints. Pig breeds selected are commonly used for pork production. Waldo Farms (DeWitt, NE) supplied the spring-summer group of pigs. The summer-fall group of pigs was born to the University of Wyoming Research and Extension Center farm.