The effect of testosterone on the social hierarchy formation of Nelore bulls

• Grant number: 19/14068-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2019
• End date: November 30, 2020
• Field of knowledge: Agronomical Sciences - Animal Husbandry
• Principal Investigator: João Carlos Pinheiro Ferreira
• Grantee: Caique Marques Marcelino
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

Disputes between confined beef cattle are quite common and can cause injury and stress, impoverishing the welfare state of animals. There are several factors that influence the motivation for the expression of agonistic behaviors. However, it is not yet known whether the decrease in testosterone levels can alter the amount of social interactions, interfering with the social order of a group. Therefore, this project aims to investigate whether testosterone could modulate the hierarchical formation in groups of bulls nelores. For this purpose, the behavior of fourteen male Bos taurus indicus during social interactions will be evaluated in situ, before and after orchiectomy. It will be used the frequency of headers, attempt of assembly, fight, lick and headplay to structure the tree of social hierarchy. The frequency of social behaviors before and after castration will be compared by applying the Wilcoxon t-test depending on the distribution of variables ensured by the Shapiro-Wilk test. The order of the bulls in the social hierarchy will also be compared before and after procedure observing the position of each bull. We hope with such results to better understand the interference of testosterone in the agonistic behaviors, aiming to guide the creators of how to regroup batches of cattle with less negative impact to the welfare state of the animals.