Laser and thermographic infrared temperatures associated with heat tolerance in adult rams

Abstract Heat is a major factor limiting the production of animals in the tropics. Sheep are well adapted to diverse ecosystems, however, temperature and relative humidity can influence animal husbandry. Therefore, this study was carried out to verify the thermoregulation in rams of six breeds (Bergamasca, Dorper, Ile de France, Hampshire Down, Santa Ines and Texel) through the evaluation of physiological traits, body measures, laser and thermographic infrared temperatures as well as testicle morphometry associated with heat tolerance. Animals were measured and weighed, coat and hair colour determined, as well as physiological traits and laser and thermographic infrared temperatures measured twice a day. Data were analyzed with the Statistical Analysis System ® . There were differences among breeds for most of the traits linked to heat tolerance, with the Santa Ines showing better adaptation to heat stress compared to other breeds. The Dorper was not significantly better than Bergamasca or Hampshire Down breeds, while Texel and Ile de France were less well adapted. Scrotal temperatures were lowest in Hampshire Down and Dorper, while highest in Texel. Temperature gradient measured by thermography identified Hampshire Down as the least heat tolerant breed. Traits linked to heat tolerance should be taken into consideration when choosing breeds for lamb production in tropical regions.