Epsilon Archive for Student Projects

Abstract

The microorganisms found in the reproductive tract of dairy cows are essential for keeping the
symbiosis balanced and healthy. They help protect against harmful bacteria and can influence
overall fertility. Dysbiosis, the state when the balance of these microbes is disturbed, can lead to
infections or other problems that might affect the cow’s ability to reproduce successfully. Understanding how these microbial communities work together can provide insights into improving
reproductive health and fertility in dairy cows.
This thesis aims to investigate what constitutes the normal vaginal flora in healthy heifers and
examines whether any differences exist between the vaginal bacteria of those heifers that become
pregnant and those that do not, the first time they are inseminated. Most currently published studies on the subject have investigated the bacterial flora when the cow is already experiencing
sickness or fertility issues such as endometritis, retained placenta and metritis, whereas this study
aims to show what is present before the heifer is first inseminated, as well as how the microbiota
changes after insemination.
The study was conducted by sampling bacteria from the cranial vagina of healthy heifers prior
to first insemination (D0) and within six days post-insemination (D6). Double guarded vaginal
swabs were used for sampling and were plated out on four different agar media within 1-2 hours
after sampling. Chocolate and blood agar plates were incubated at 37 °C with 5% CO2 for
24+24h. Lactose purple agar, and mannitol salt agar plates were incubated at 37 °C for 24+24h.
Bacterial colonies were identified by Matrix-Assisted Laser Desorption / Ionization Time of Flight
Mass Spectrometry (MALDI-TOF MS). Our findings showed that the microbiota in the vagina of
heifers mainly consisted of Actinobacillus seminis, Streptococcus spp., Histophilus somni and
Bacillus spp. both before and after artificial insemination. However, Staphylococcus spp. were
more often isolated from the group of heifers that did not become pregnant at first insemination.
This study provides valuable knowledge into the microbial species inhabiting the reproductive
tract of dairy cows, underscoring the necessity of understanding the roles of these communities for
enhanced reproductive outcomes and herd health. Further research is needed to explore the specific roles and interactions of these microbial species in the reproductive tract of cattle and the
environment.
Keywords: AI, artificial insemination, cattle, bacteriology