doi:10.1016/j.smallrumres.2025.107679engPérez-García, ElenaNieto, JaimeAbecia, José AlfonsoPlaza, JavierPalacios, CarlosAssessment of sexual activity in rams stimulated with artificial light and its impact on unstimulated rams during the initial 14 days of male effectART-2025-146986Seasonal anoestrous reduces reproductive efficiency in sheep in temperate regions. Artificial photoperiod manipulation is a non-hormonal approach that stimulates ram sexual activity and enhances the "ram effect" on ewes. This study evaluated the sexual behaviour of rams subjected to artificial long-day photoperiods (L group) and their effect on non-stimulated rams (C group) during the first 14 days after introduction to anoestrous ewes. Eleven rams were assigned to photostimulated (n = 6) or control (n = 5) treatments, forming four groups: L, C, L+C (stimulated rams exposed to controls), and C+L (controls exposed to stimulated rams). Continuous video recording documented 5707 behavioural events. Photostimulated rams (L) exhibited higher activity (mean = 747.7 behaviours/ram) than other groups (C+L: 519.5; L+C: 443.0; C: 365.3; p < 0.01), with anogenital sniffing, approaching and chasing ewes being the most frequent behaviours. Activity peaked on days 2–5 post-introduction, mainly in the afternoon. Control rams housed with stimulated rams were more active than isolated controls, suggesting a social facilitation effect. These findings confirm that photoperiod manipulation enhances ram sexual activity and may influence non-stimulated rams through social interaction, as the different groups of animals exhibited distinct types and amounts of activity2025http://zaguan.unizar.es/record/16529610.1016/j.smallrumres.2025.107679http://zaguan.unizar.es/record/165296oai:zaguan.unizar.es:165296Small Ruminant Research 255 (2025), 107679byhttps://creativecommons.org/licenses/by/4.0/deed.esinfo:eu-repo/semantics/openAccess