Factors Associated With the Development and Prevalence of Abnormal Behaviors in Horses: Systematic Review With Meta-Analysis.

Researchers believe that the development and prevalence of abnormal behaviors in horses may be caused by several environmental and biological factors, and the literature offers numerous reports that discuss the causes and effects of stereotypies in these animals. In this light, this study aimed to conduct a systematic review and meta-analysis of the scientific literature, summarizing the main risk factors associated with the development of abnormal behaviors in horses. The searches were conducted over the course of four years in Portuguese, Spanish, and English. The publications reviewed were full text research thesis or articles that addressed issues within the following criteria: (1) presentation of epidemiological information on the studied population; (2) prevalence of abnormal behaviors in equine populations; (3) factors associated with the development or prevalence of stereotypies. Data were extracted from each study and inserted into an Excel spreadsheet to be analyzed through descriptive statistics. In addition, the Mann-Whitney U test was used to verify the existence of significant differences between the methodologies (direct observation/questionnaires). The dataset was also analyzed through data mining to identify the main factors that influence the prevalence of abnormal behaviors in the studied population. The results showed a great variation in the mean prevalence of abnormal behaviors, with no significant difference between research conducted through questionnaires or direct observation, and the data mining technique identified that incorrect nutritional management may be the main factor influencing the development and prevalence of abnormal behaviors in horses.