Incubation of bovine semen samples in thermoresistance test (TTR) and its relationship with fertility rates in artificial insemination programs

Abstract

Reproduction biotechnologies play an essential role in increasing the productive efficiency of Brazilian cattle herds. Therefore, laboratory studies related to the reproductive performance of these animals are important to innovate practices that increase their reproductive capacity, especially in male bovines. Post-thaw semen analysis is essential to produce quality material. In addition to the qualitative and quantitative analysis of sperm, other complementary tests can be performed, such as the thermoresistance test (TTR), which assesses the resistance of spermatozoa at high temperatures for a short period (fast thermoresistance test; TTR/R) or in cow physiological temperature for a longer incubation period (slow thermoresistance test; TTR/L). However, there are still questions about which test to use (TTR/R or TTR/L), the incubation time, and its relationship with fertility rates in artificial insemination programs. Thus, the objective of the study will be to evaluate three incubation periods of semen samples in the TTR/R and TTR/L tests. In addition, it will also be evaluated whether there is a positive correlation between the semen samples that resist a higher temperature or a longer incubation period with the fertility index (pregnancy rate). 10 different batches of 08 Nelore bulls and 08 Angus bulls with pregnancy rates will be used in artificial insemination programs ranging from 45 to 75%. Semen samples will be thawed at 37°C for 30 seconds and then incubated in closed straws for 30, 45, and 60 minutes at 46°C and 3, 5, and 8 hours at 38°C. Semen samples will be evaluated at all periods using a computerized sperm analysis system (CASA) and plasma membrane integrity. The analysis of results will be evaluated using the SAS statistical package. (AU)