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GnrrNnrnc, L. G. nNo ManoNs, J. P. I 981 . The effect of a 15-h photoperiod on reproductivefunctioninboards at2,3,4 or5monthsof age. Can. J. Anim. Sci. 6l:925-934.The effects of supplemental lighting in stimulating reproductive function in prepuberal boius were studied using littermate boars divided equally into four groups (n : 9). All boarsreceivednatural daylighr(9.2 12.8h)until 2moofage,followedbyarrificiallight given daily according to the following schedule: boars wereexposed to a 15-hphotoperiod beginning at the age ot 2 (group I); 3 (group II); 4 (group III) or 5 mo (group IV). Libido scores of the four groups increased with age (P < 0.001 ). Seminal plasma protein (P < 0.01) and zinc concentration (P < 0.05), sperm-rich concentration, sperm-rich volume, total semen volume and total viable sperm increased (P < 0.05) with age in all four groups. The photoperiod treatment had no effect on semen quality on a per ejaculate basis between the groups; 15 h of light per day was not effective in accelerating the onset of puberty when administered from 2, 3, 4 or 5 mo of age onward.Dans cette 6tude sur des verrats pr6pub6raux, l'utilisation d'un 6clairage prolong6 d 6t6 6valu6e comme moyen de stimuler leur efficacit6 de reproduction. Chacun des groupes avait la m6me composition quant i l'origine maternelle des verats. Le programme d'dclairagea6t6 lesuivant: naturel (9.2-12.8h) jusqu'dl'dgede2mois, l5hdelumidre