Melatonin implantation and dietary energy level in relation to locomotor activity rhythms in ewes

This study evaluated the effects of melatonin implantation and dietary energy level on locomotor activity and the 24-h activity rhythm in adult ewes. Twelve adult Rasa Aragonesa ewes were allocated to a 2 × 2 design with melatonin implantation (+ MEL or − MEL) and dietary energy supply (1.5 or 0.5 times maintenance requirements; three ewes per combination). Neck-mounted accelerometers recorded activity over 15 days. Individual 24-h cosinor models described activity level, amplitude and acrophase. Melatonin-implanted ewes showed numerically lower mean locomotor activity (0.0183 versus 0.0242 g) and smaller fitted daily amplitude. However, the treatment differences were not significant in a subsequent ewe-level permutation sensitivity analysis (MESOR P = 0.065; amplitude P = 0.110). The exploratory design, small sample size and lack of replicated pens for dietary treatments limit causal interpretation.