Behavioural study of rams subjected to photoperiod change: sexual, social, vital and group activities monitored by video

This study examined behavioural differences in rams exposed to artificial photoperiod stimulation, within the context of the ram effect. Eleven rams were divided into two groups: six received two months of long-day artificial photoperiod (16 h light/day), followed by one month of natural light (9 h light/day, February), while five control rams remained under natural lighting. At the end of the third month, three pens were established: one with photoperiod-stimulated rams (Group L, n = 3), one with control rams (Group C, n = 3), both with 30 ewes, and one mixed pen with both stimulated (Group L+C, n = 3) and control rams (Group C+L, n = 2) with 60 ewes. Behavioural observations were conducted over 11 consecutive days. A total of 26 behaviours-classified as sexual, vital, social, and grouping- were manually recorded and analysed using BORIS software. Sexual behaviours were the most frequent across all groups. Rams in Group L exhibited higher frequencies in all behaviour categories (p < 0.001). Vital activities had the longest durations, with Group C spending more time on these behaviours than others. In the mixed pen, both stimulated and control rams showed intermediate activity frequencies compared to their respective isolated counterparts (Group L: 36.7 % vs. L+C: 26.6 %; Group C: 17.6 % vs. C+L: 19.0 %; p > 0.001).

In conclusion, artificial photoperiod stimulation increased the frequency of key behavioural categories, especially sexual activity. Social interactions in mixed groups modified behaviour, suggesting mutual influence. BORIS software proved valuable for detailed behavioural analysis in ethological research.