It is consensual that the animals of the breed Morada Nova have capacity to withstand heat stress, nutritional and sanitary stress at any time of the year. These attributes, cited as main advantages by almost all breeders, justify the adoption of this breed in extensive systems in the Brazilian semiarid environment. Selection for more adapted animals was for a long time based only on the maintenance of body temperature, but it is known that there are several factors related to adaptation as physiological, blood and morphological parameters. It is important to know what adaptive characteristics may be indicative of thermal stress so that they can be included in genetic breeding programs in order to obtain better results in the use of these animals in the living environment. The objective of this study was evaluate the behavior and magnitude of morphological, thermoregulatory and blood parameters of Morada Nova sheep throughout the year in the participating properties of the Participatory Genetic Improvement Center. Animals from 4 flocks were evaluated in the months of March, June, September and December. The thesis was divided into two chapters; the first one aimed to evaluate the behavior and magnitude of the thermoregulatory responses of Morada Nova sheep throughout the year, and it is hoped to provide subsidies to indicate a phenotypic marker of thermotolerance, so that these can be used as selection criteria in programs for the conservation and genetic improvement of heat-resistant animals. The rainy season was considered the most stressful for the animals in the present study, by the more intense use of a set of variables in order to thermoregulate and maintain the homeothermia. The behavior of coat characteristics may favor the animals during all the months of the year for either physical protection or heat dissipation and could thus be indicated as a phenotype thermotolerance marker to possibly be used with criteria in breeding programs and genetic conservation of heat resistant animals. The second chapter aimed evaluate the behavior of hematological parameters and blood metabolites of Morada Nova sheep, associating the environmental conditions of the Brazilian semiarid at different seasons of the year. The biochemical and hematological parameters of the Morada Nova sheep were, for the most part, within the physiological levels considered normal for the species. The variations observed in the hematological and biochemical parameters reflect the adaptability and plasticity of Morada Nova sheep in response to the management conditions and the environment to which they were submitted