Correlação entre parâmetros cinéticos do sêmen e produção in vitro de embriões em bovinos da raça Girolando

Abstract

Brazil is one of the largest cattle producers in the world, with a herd of approximately 213 million heads distributed throughout the national territory. The Girolando breed stands out in the dairy herd due to its rusticity and easy adaptation to the tropical climate, being the breed responsible for the higher percentage of national milk production. In order to achieve this performance, national livestock farming has been improved over the decades with the application of technology in the field and genetic improvement programs. Reproductive biotechniques, including the in vitro embryo production (IVEP), contributed to this process by offering safe laboratory production and accelerating the process of genetic improvement. Thus, softwares have been used to improve herd reproduction rates, such as embryo production rates and sperm analyzed parameters. The computer-aided sperm analysis system (CASA) assists in the andrological examination and provides relevant information about semen kinetic parameters such as progressive motility (PM), linearity (LIN), straightness (STR), wobble (WOB), curvilinear velocity (VCL), straight-line velocity (VSL), average path velocity (VAP), amplitude of lateral head displacement (ALH), and beat-cross frequency (BCF). These parameters assist in the clinical analysis of semen and can validate a sample for use in animal reproduction. However, these parameters together could represent a correlation with fertility rates and embryo production. Principal component analysis is a multivariate statistical method that turns studied variables into components, diminishing a large amount of data into a few components, facilitating analysis and correlating the acquired components with a studied event. In this research, semen samples from five Girolando bulls were used for in vitro embryo production; cleavage and blastocyst rates were assessed. Subsequently, three semen samples from each bull (from the same batch used for fertilization) were analyzed using CASA. The averages for the parameters examined for each bull were correlated with cleavage and blastocyst rates using principal component analysis. The first component (PC1 – 70%) demonstrates that curvilinear velocity (VCL) and average path velocity (VAP) had higher correlation with in vitro embryo production.