Effect of transport on body temperature and heart rate of lambs measured by subcutaneous bio-loggers

The transport of livestock is an animal welfare issue, but an essential activity in the meat production system. During transport, animals are exposed to a variety of environmental stressors. The shifts in temperature, vibration, noise, stocking density, and human handling represent some of the most common physical and psychological discomforts. We have used subcutaneous bio-loggers to determine the effect of transport on body temperature (T, °C) and heart rate (HR, bpm) of lambs, as potential indicators of stress. Eighteen 90-day-old lambs were surgically implanted with a subcutaneous T and HR bio-logger (DST micro-HRT, Star Oddi, Iceland), which was programmed to record data at 1-min intervals. The day of transport (75 min) was divided into seven phases (2h before transport; loading; lambs loaded in the stopped lorry; transport; unloading; 1st h after transport; 2nd h after transport). Mean (±S.E.) T and HR were calculated and compared by ANOVA; differences among phases was evaluated by the Tukey test. Lambs presented the same T 2h before transport (38.90±0.01) and the 2nd h after (38.89±0.01), reaching a peak when the lorry was stopped (39.15±0.02), and 1h after the transport (39.00±0.01) (P<0.001). No differences were observed for T during load, trip and unload (38.72±0.03; 38.63±0.01; 38.72±0.06, resp.), which were significantly lower than 2h before the trip (P<0.001). Lambs had similar HR during the 2h before the transport (122.12±0.69), trip (122.99±0.72), unload (128.00±2.84), and the 2nd h after transport (120.45±0.53). They reached the maximum HR during loading (136.04±1.82) and the 1st h after transport (134.46±0.83). In conclusion, the bio-loggers used in this experiment have demonstrated a high sensibility to detect changes in T and HR of lambs before, during and after a stressor as transport. For T, transport produced a hyperthermia when the lorry was not in movement and a higher HR during loading.