The thermoregulatory capacity of calves is not yet well defined. Young animals raised in environments with adverse thermal conditions have difficulty adjusting their physiological responses, mainly due to high temperatures and thermal radiation levels. Infrared thermography is a valuable and non-invasive tool for assessing the thermal stress status of animals. The analysis of thermal images to detect situations of thermal stress and health status has grown in recent years. Thus, this book provides important information for understanding the physiological adjustments of calves throughout the day in a hot environment through invasive and non-invasive measurements (infrared thermography). The authors emphasize the importance of studying animals with a non-invasive method in order to avoid stressful situations.