The study investigated the relationship between the temperature humidity index (THI) and the behaviour of 24 young fattening Limousin bulls reared in two farms in Tuscany, Italy. In each farm, six animals were undergone to ceiling fans (switched on at THI values up to 72), and six animals represented the control group. The trial lasted three days for two consecutive weeks in August 2020. Behavioural observations were conducted using scan sampling technique and eating, ruminating, drinking, resting and other social activities were registered every 5 min, from 9.30 am to 4.00 pm. Two different microclimatic conditions were evaluated to assess the effect of the ventilation system: normal (THI < 78) and alert (THI ≥ 78) conditions. Results showed that the ventilation system had significant effects increasing inactivity and lying down compared to control groups and decreasing eating and drinking activities. THI alert condition caused a significant decrease in eating and an increase in lying down behaviours. Ventilation system did not influence the animals’ cleanliness. The ceiling fans’ efficiency in changing the behaviour of young fattening bulls was demonstrated but further studies are needed to assess the ventilation system effects, especially during longer heat stress periods.
Keywords: Limousin beef cattle; ceiling fan; heat stress; social behaviour.