Influence of artificial light regimens on sexual maturation and boar taint in entire male pigs.

To determine if artificial light regimens could influence sexual maturation and boar-taint factors in entire male pigs, 48 weaned, winter-born crossbred males (52-64 days old) were exposed to either a natural photoperiod (January-June, 60 degrees N, Control, n= 16) or to one of two artificial photoperiods (1400 1x) in light-sealed rooms. We exposed the Spring group to an increasing artificial photoperiod (January - June, 60 degrees N, n=16) and the Autumn group to a decreasing one (July-December, 60 degrees N, n = 16). Plasma samples were collected bi-weekly until the pigs were slaughtered, after reaching 115 kg. Boar taint, carcass composition and reproductive traits were measured at slaughter. Plasma testosterone increased earlier in the Autumn group than in the Control and Spring groups, but the difference was only transient. Estrone sulfate concentrations remained low in the Autumn group, whereas they increased in the Control and Spring groups, indicating a lack of synchrony between testicular androgen and estrogen production in the Autumn group. In the beginning of the study, when the Autumn group was subjected to long days, plasma prolactin was higher in the Autumn group than in the Spring group, but the relation was reversed 14 weeks later when the spring group was exposed to long days. Weight of reproductive organs (epididymidal weight and the total weight of the testes, epididymides and the bulbourethral glands relative to carcass weight) were lower in the Autumn and Spring groups than in the Control group. The Spring and Autumn groups had lower concentrations of skatole in fat compared with the Control group, whereas no clear difference was detected between groups in concentrations of androsterone in fat or in the sensory evaluation of boar taint. Estimated lean meat percentage was lower among animals in both the Autumn and Spring groups compared with the Control group. This study shows that photoperiod can influence male pubertal development and boar-taint factors in the domestic pig.