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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.

Native to South America, the Rhea americana is the largest bird of this continent. In Brazil, they are native to the South, Southeast, Midwest, and Northeast, with the exception of the coastal strips. Birds, in general, have the ability to maintain their body temperature constant, losing to the environment the additional heat that is produced. In this attempt to maintain thermal equilibrium, animals use non-evaporative and evaporative mechanisms to exchange heat with environment. Behavioral changes are also common as strategies aiming heat loss to the environment. Behavior changes are the main adaptive responses of animals to various environmental stimuli and studies addressing the thermoregulatory behavior of the animals are essential to the improvement of management and production systems. The thermal changes probably occur through a set of behaviors that combined helped to maintain the homeothermy of birds. Research on thermoregulation and the behavior of Rhea are still scarce. In this context, this article presents an initial approach to the thermoregulation, from a behavioral perspective, of Rhea (Rhea americana) in hot climate regions.

No abstract

The electrolyte balance of the diet is defined as the difference between the main cations and anions of the diet. As in heat stress situations the respiratory rate rises, there is an increase in the carbon dioxide loss which reflects in the reduction of the partial blood pressure of CO2, and an elevation of the blood pH. The electrolyte balance of the diet can influence appetite, bone development, response to heat stress and the metabolism of amino acids, minerals, and vitamins. In the last years, it has been verified that the diet manipulation can be a way to improve the quantitative and qualitative performance of laying birds, appearing as a viable nutritional alternative and of easy practical application. In this context, this mini-review aims to approach the main aspects of the electrolytic balance in the diet of laying birds.