## 1 Introduction  
During the ongoing automation of dairy farming, objective and reliable tools for diagnosing the condition of animals are in great demand. It is necessary to evaluate milk yield, the parameters of milk produced and the general condition of the animal [1, 2, 3, 4, 5]. Animal productivity is influenced by many factors, such as the interaction between animals and humans [6]. The temperature of the udder surface skin temperature is indicative for determining the condition of the animal, due to the potential influence of various diseases on it. Masitis is one of the most common diseases that can affect the health of the udder and the quantity and quality of milk yield. The bacterial species _S. aureus_ is the most common causative agent of mastitisti in cows in most countries with a dairy industry [7]. Early detection of mastitisti, carried out by rapid automatic monitoring, can be a way to increase the efficiency of milk production [8]. The lack of timely treatment of mastitis due to a long detection can lead to large losses of milk, as well as a chronic decrease in cow milk yield. Timely and modern treatment of mastitis will help to avoid large losses of milk [9, 10]. Mastitis is the most detrimental disease for the farm.  
In most cases, mastitis leads to an increase of the udder surface skin temperature [11, 12]. Measuring the temperature of local areas of the udder surface skin using spectral equipment is a fast, automated and effective way to diagnose the physiological state of the animal [13]. The analysis is carried out within a few minutes and the results can be obtained immediately. This method is accurate in detecting abnormal animal health and reduces the amount of labor on the farm. It is also important to distinguish inflammation from diurnal fluctuations in under surface skin temperature and changes in room temperature [14; 15; 16]. Also, the temperature of the udder surface skin can be affected by milking [17]. For cows with udder disease, the infrared temperature image of the udder differs significantly from that of cows with healthy udders [18; 19]. In addition to an increase in temperature, mastitisis is also characterized by an increased content of somatic cells in milk [20]. Somatic cell count is another way to identify mastitis [21; 22].  
The usage of infrared thermography to determine the temperature thresholds of the udder surface skin is a fast and non-invasive way to immediately obtain information about the condition of the animal in the cowhold and to assume a change in milk yield [23; 24]. The study of the temperature of the skin of the udder of cows of the Yaroslavl breed to determine the threshold values for inflammation, presumed mastitisis and even its type, will make significant progress in the implementation of a rapid system for assessing the condition of animals.  
The main purpose of this work was to explore the udder surface skin temperatures and changes in milk yields of cows with different health conditions, to search for a dependence between temperatures and milk yields, and to determine the threshold values of udder surface skin temperatures that indicate inflammation of the udder. The result of the study should be the development of an algorithm that allows for drawing conclusions about the state of the animal's udder based on the thermogram and suggesting a change in milk yield.