Broilers’ behavioural adjustments when submitted to natural heat stress and fed different maize particle sizes in the diet

• Published in: The Journal of agricultural science 2019-12, Vol.157 (9-10), p.743-748
• Main Authors: Santos, M. M., Souza-Junior, J. B. F., Queiroz, J. P. A. F., Costa, M. K. O., Lima, H. F. F., Arruda, A. M. V., Costa, L. L. M.
• Format: Article
• Language: English
• Subjects: Animals; Behavior; Birds; Corn; Diet; Drinking water; Energy efficiency; Environmental monitoring; Feeds; Heat; Heat stress; Heat tolerance; Humidity; Overheating; Particle size; Thermal environments; Thermal stress; Thermoregulatory behavior; Time of use
• ISSN: 0021-8596; 1469-5146
• DOI: 10.1017/S0021859620000131

Since behavioural adjustments are an important line of defence against thermal stress, either due to their energy efficiency or to efficiency at preventing overheating, we aimed to evaluate whether broilers fed different maize particle sizes adjusted their behaviour to deal with heat stress challenges. At several times a day, the behaviour of 220 naked neck broilers was evaluated. These broilers were fed with isonutritive diets containing maize with different geometric mean diameters (GMD): 605 and 2280 μm. The thermal environment was monitored during the experiment. Panting and open wings were the only behaviours that showed differences between the times of day ( P < 0.05). However, GMD showed a significant effect on feed intake and panting ( P < 0.05). The interaction between GMD and time of day was significant only on panting ( P < 0.05). Although no daily variation was observed, the highest feed intake was observed in broilers fed the diet containing maize with a GMD of 2280 μm. Less than 5% of the broilers were observed drinking water during the day. Open wings was the behavioural adjustment most used by broilers from 10:00 h, and remained elevated until 14:00 h for both GMDs. The birds panted more when fed the diet containing maize with a GMD of 2280 μm. In conclusion, broilers adjust their behaviour to dissipate excess body heat from the environment and as a result of feed intake. Coarse particles of maize in the diet increase the thermal challenge of broilers since the environment also provides stressful thermal conditions.