The influence of the 5-Hydroxytryptamine Receptor 2A ( <i>HTR2A)</i> gene polymorphism on the temperament of Polish Red cows by using Classification and Regression Trees <i>(CART)</i>

Abstract Temperament is an important behavioural feature in breeding cattle. It is inheritable, and so is a factor in selection programmes in some countries. In recent years, several dozen genes that might significantly affect cattle temperament have been identified, including the serotonin receptor 2A ( HTR2A ) gene, but its polymorphism was only analysed for its production value, especially among high-production breeds. The goal of this study was to analyse the polymorphism of the HTR2A gene in a native conservation Polish Red Cattle breed using the decision tree. In this study, 124 Polish Red cows were genotyped using Sanger sequencing. Statistical analyses included the method of data exploration known as the classification and regression tree and the chi-square test of independence, which offered a precise description of the relationship between cattle temperament and genotype. Two mutations, rs110801604 and rs43696136, proved to be closely related to temperament, as animals with extreme temperaments (calm and excitable) had different genotypes in those loci . These promising results indicate that further research into the polymorphism of the HTR2A gene is warranted for cattle of different breeds and purpose.