Banca de QUALIFICAÇÃO: CHARLENE KAROLLAINE DE CASTRO DOURADO

INFLUENCE OF THREE MANAGEMENT SYSTEMS ON THE SPERMATIC QUALITY OF NELORE BULLS

thermal stress; semen; sperm pathologies; infrared thermography.

Brazil maintains a prominent role in the international market, being the world's largest exporter of beef. In this context, cattle farming demonstrates its importance to the Brazilian economy, especially in the field of animal reproduction, which is essential for the maintenance and expansion of the herd. The experiment will be conducted at Fazenda Santo Antônio, located in the rural area of the municipality of Mojuí dos Campos. Fifteen non-castrated Nelore bulls with similar coloration, aged between 18 and 20 months, weighing an average of 250 kg, with a body condition score of 3.5 (on a scale of 1 to 5), clinically healthy, will be used. They will be randomly divided into three groups: Traditional System - TS (n=5), Silvopastoral System - SS (n=5), and Integrated System - IS (n=5). The TS group will be placed in a paddock without tree shade, with Brachiaria brizantha cv. Marandú pasture, access to drinking water, and ad libitum mineral salt. The SS group will remain in a paddock of the same size, with about 20% shade from Brazil nut trees (Bertholletia excelsa), access to drinking water, and ad libitum mineral salt. The IS group will stay in a paddock of the same size and pasture, but with access to 20% shade from Brazil nut trees (Bertholletia excelsa), and access to water for drinking and bathing, as well as ad libitum mineral salt. Semen will be collected using an electroejaculator (Boijektor-2001). Each bull will be individually restrained, and the electrostimulation technique will be performed until ejaculation is achieved. After each collection, the macroscopic physical analysis of the ejaculate will be conducted, observing the volume (VOL) directly in the graduated tube and the appearance of the semen (ASP), which will be classified from 1 to 4, with 1= watery, 2= opalescent, 3= milky, and 4= creamy. For microscopic physical evaluation, a drop of semen will be placed between a slide and coverslip preheated to 37°C, and the reading will be performed using an optical microscope under bright field at 100x magnification. The microscopic characteristics evaluated will be: progressive motility (MOT), expressed as a percentage, sperm vigor (VIG), and swirling (TURB), expressed on a scale of zero to 5. After conducting the mentioned macro and microscopic physical evaluations, two samples will be collected in a formal-citrate solution for subsequent analysis of sperm concentration (CONC) and morphology. The morphological characteristics will be classified into major defects (MDe), minor defects (Mdi), and total defects (TD). For characteristics that meet the assumption, parametric analyses will be conducted, and for variables that do not show normality, non-parametric analysis will be performed. The variables will be compared according to the type of system used (shade with access to a bathing area vs. shade without access to a bathing area and no shade and no access to a bathing area) through univariate and/or multivariate mean comparison tests. The analyses will be conducted using the Statistical Analytics System software.