Effect of nocturnal feeding on locomotor activity and rumination rhythms, and sleep/wake cycle in diurnal dromedary camels

The dromedary is a desert animal that is most active during daylight and rests at night. In its natural habitat, it spends most of the day grazing, whereas in an intensive livestock farming system, food availability is programmed by humans. Temporal feeding exerts a strong influence on the circadian rhythms of numerous species. These aspects have become challenging in camel husbandry, which has recently faced important changes, moving from extensive management with free grazing in the desert to urban and peri-urban intensive farms with various feeding schedules. The objective of the present study was to examine the impact of altering feeding schedules on the locomotor activity (LA), rumination rhythms and the sleep-wake cycle of dromedaries. The study involved four female camels that were housed under semi-natural environmental conditions mimicking an intensive livestock farming system. The study was conducted over three periods of 3 weeks each, with a fixed, non-counterbalanced feeding sequence, during which food was distributed either at 10 a.m. (stages 1 and 3) or at 10 p.m. (stage 2). Behaviour was recorded continuously, and polysomnography (PSG) was performed during the final 48 h of each stage. Shifting food access from 10 a.m. to 10 p.m. induced an increase in the amount of nocturnal activity from 0.6 h (stage 1) and 0.8 h (stage 3) to 4.1 h (stage 2). Conversely, the daytime activity level decreased when food was available during the night. While diurnal rumination remained unchanged, shifting food access reduced the nocturnal duration of rumination from 4.3 h and 4.7 h (stages 1 and 3, respectively) to 2.8 h (Stage 2). Nocturnal feeding was associated with anticipatory bouts of locomotor activity (FAA), which continued for 3 d after switching back to diurnal feeding. Polysomnographic results revealed that nocturnal feeding decreased TST (Total sleep time) during the night, from 27.82% (Stage 1) and 27.04% (Stage 3) to 21.39% (Stage 2). Conversely, a sleep rebound was characterized by a daytime increase in TST from 1.7% and 1.3% to 7.6% when feeding was at 10 p.m. In conclusion, the findings indicate that in camels, nocturnal feeding was associated with marked changes in the temporal organization of LA, rumination, and sleep-wake cycle. While the overall daily amounts of these behaviours were largely maintained, their redistribution across the 24-h cycle suggests that feeding time can modulate circadian outputs. These results highlight the importance of taking into account the natural temporal organization of the species, when designing feeding schedules in camel husbandry, while acknowledging that further studies are needed to assess the long-term physiological and welfare implications.