Circadian, feeding, and locomotor activities of artificially reared lambs measured by actigraphy

Abstract

Eight artificially reared lambs were used to study locomotory and feeding activities in the first three weeks of life by actigraphy. Lambs were fitted with a Bluetooth-enabled (BT) accelerometer and data were downloaded as activity counts at 1-min intervals (Vector Magnitude, VM). Sensors were programmed to act as beacons, and two sensors programmed as receivers were installed next to the rubber nipples of the milk feeder and recorded the serial numbers and labels of other nearby beacons through the BT signals. Mean (±SE) VM was 140 ± 3 counts/min, and time of day and week had significant (P < 0.001) effects. Overall activity did not differ significantly between sexes (males: 139 ± 5; females: 142 ± 5). The proportion of lambs that exhibited a 24-h circadian rhythm decreased with age (week 1 = 75%, week 2 = 63%, week 3 = 50%). Mean number of suckling sessions/day was 3.7 ± 0.2, the mean number of minutes suckling/day was 12.5 ± 0.9, and mean number of minutes/meal was 3.5 ± 0.2. Males dedicated more time/meal than females (males: 4.1 ± 0.4; females: 3.0 ± 0.2 min; P < 0.05). In conclusion, actigraphy is a useful tool for investigating the locomotor and feeding behaviour of artificially reared lambs, which detected a reduction in the circadian rhythmicity and the number of suckling sessions with age.