Aggression as a behavior is not always desirable, often ends in abandonment and/or euthanasia. However, it is possible to prevent the occurrence of unwanted aggression in domestic dogs. Aggression is not a fully understood phenomenon. In recent years, many studies have focused on the influence of diet and physiology (including the endocrine system) on the emergence of behavioral disorders. In particular, the emphasis was put on nutritional additives such as fatty acids, amino acids, and probiotics. In addition, the possibility of using neurocognition in the observation of abnormal behavior in dogs has also been discussed, which may allow for a more detailed determination of the basis of aggressive behavior in dogs. In this review, the concepts related to aggression and its potential causes have been gathered. In addition, the possible influence of diet and hormones on aggression in dogs has been discussed, as well as the application of neurocognition in the possibility of its diagnosis.

The microbial community of the gastrointestinal tract in animals and humans plays one of the key roles in the decomposition of nutrients and maintaining the organisms in homeostasis. Dysbiosis of microbial community in the gastrointestinal tract could be caused by environmental or biological factors and additionally effect on behavior of dogs. The purpose of this study was to evaluate the level of main bacteria in feces from dogs with behavioral disorders and compare dogs without behavioral disorders. Two study groups participated in the experiment: healthy dogs (n=3) and dogs with behavioral disorders (n=7). Fecal samples were collected individually from each individual for a period of 4 weeks (1 sample/week), and then bacterial DNA isolation and real-time PCR were performed for the main bacterial phyla (Firmicutes, Bacteroidetes, Proteobacteria) and families (Lactobacillaceae and Clostridiaceae). Subsequently, analysis of cortisol levels from previously collected fecal samples was performed to determine the level of physiological stress. In addition, behavioral analysis was performed in the ethograms of all individuals. The results obtained showed significantly higher levels of the Firmicutes in dogs from the control group compared to groups with behavioral disorders. In the case of the cortisol test, significant differences in cortisol levels between individuals have been shown.