Aspects of thermoregulation of goats in hot environments
Juliana Jéssica Ferreira Coelho Silva and Leonardo Lelis de Macedo Costa
ABSTRACT In the course of the years, goat farming has been demonstrating its socio-economic potential, which encompasses all its production chains, presenting favorable results for a positive economic yield. Goats are classified as homeothermic, where they present physiological mechanisms with the purpose of maintaining constant body temperature inside of a certain ambient temperature range, denominated thermoneutrality zone. In this context, this review aims to address the thermoregulation aspects of goats when submitted to hot environments. Commonly in a tropical environment, the air temperature generally approaches or exceeds the body temperature of the animals, thus the sensible heat loss becomes ineffective. In these adverse thermal conditions, the evaporative heat loss mechanisms are more effective, making them essential for the thermal regulation to occur because it does not depend on the temperature differential between organism and atmosphere. This evaporative thermolysis may occur on the body surface and in the respiratory tract, but the cutaneous evaporation corresponds to the greater portion of heat dissipated. Cutaneous evaporation becomes even more important if goats are exposed to direct solar radiation, which is three times larger the value for shaded goats. Therefore, the knowledge of which thermoregulatory mechanisms can be used by goats and how they work in hot environments is of fundamental importance for the planning of an efficient production system. In addition, providing subsidies for a correct decision making in possible abrupt variations that can occur in the micro or macroclimate in which the animals are being raised.
KEYWORDS: biometeorology; cutaneous evaporation; small ruminants; physiological responses; semi-arid