Influence of light environment and photoperiod on plasma melatonin and cortisol profiles in young domestic boars, comparing two commercial melatonin assays.
Eighteen crossbred boars, three siblings from each of six litters, were distributed randomly among three groups after weaning. The 'Natural long-day' group was housed in a standard room with windows, whereas the 'Artificial long-day' and 'Artificial short-day' groups were housed in light-sealed rooms and under an artificial light regimen (1400 lx). In spring (16-17 hr of light) plasma levels of melatonin and cortisol were measured in samples collected hourly for 24 hr. Two commercial melatonin radioimmunoassays with preassay diethyl ether extraction were compared. Only the assay from Bühlmann Laboratories AG showed low to undetectable melatonin levels during the light-phase and was used for further analysis. Dark-phase melatonin concentrations were higher than light-phase melatonin concentrations (P < 0.001). Dark-phase melatonin concentrations were higher in the 'Natural long-day' group than in the 'Artificial long-day' and the 'Artificial short-day' groups (P < 0.001). Sire had a significant effect on dark-phase melatonin concentrations (P < 0.01), but not on light-phase levels. Cortisol concentrations were higher during the light-phase than during the dark phase, and light-phase cortisol concentrations were higher in the 'Natural long-day' group than in the 'Artificial long-day' and the 'Artificial short-day' groups (P < 0.01). This study showed that peripubertal boars express a typical circadian melatonin rhythm under both artificial light regimens and in standard pig stable environment. Natural photoperiod and indoor lighting seem to interact in shaping the melatonin profile in standard stable environment. The great individual variation in the amplitude of the dark-phase melatonin levels could in this study be explained by the different sires.
Andersson
H
H
Centre for Reproductive Biology, Department of Clinical Chemistry, Swedish University of Agricultural Sciences, PO Box 7038, S-750 07, Uppsala, Sweden. hakan.andersson@klke.slu.se
Lillpers
K
K
Rydhmer
L
L
Forsberg
M
M
D000818:Animals; D005260:Female; D006854:Hydrocortisone / Q000096:biosynthesis* / Q000097:blood; D007118:Immunoassay / Q000662:veterinary; D008027:Light; D008297:Male; D008550:Melatonin / Q000096:biosynthesis* / Q000097:blood; D017440:Photoperiod; D011863:Radioimmunoassay / Q000662:veterinary; D011897:Random Allocation; D013548:Sweden; D013552:Swine / Q000235:genetics / Q000502:physiology*
D008550:Melatonin; D006854:Hydrocortisone