Effects of a Ceiling Fan Ventilation System and THI on Young Limousin Bulls’ Social Behaviour

SIMPLE SUMMARY: Natural and anthropogenic factors have accelerated climate change. The frequency and intensity of summer heat waves with hot temperature and high humidity are increasing in temperate regions due to global warming. Heat might be very stressful for beef cattle reared in intensive indoor systems, impairing their health and welfare, and practical solutions should be developed and tested for its mitigation. The ceiling fans used in this study are able to slightly modify Limousin beef cattle behaviour, suggesting potential positive effects on animal welfare when ventilation systems are used during the whole heat stress period. Indeed, the number of hours with high temperature humidity index values could determine cumulated stress mainly modifying the animals’ behaviour. ABSTRACT: 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.