Low fertility can cause significant economic losses in dairy farms. Researchers from Japan investigate how microbial populations in the uterus of dairy cows may be linked to their fertility following artificial insemination, and propose microbiome testing as a potential strategy to diagnose unexplained infertility in dairy cows.
Newswise — The prolonged time between calving and conception in dairy cows, caused by reduced fertility, leads to significant financial losses for dairy farms. Reproductive failure is responsible for the culling of up to 25% of cows, surpassing other major factors such as mastitis and lameness in its impact.
Several factors contribute to low fertility in cows, including management practices like estrus detection, nutritional control, and cowshed environment. Cow-specific factors like reproductive tract infections, endocrine disorders, and defective ova also play a role. However, there are instances of low fertility where the exact cause remains unknown, resulting in economic losses. Identifying the factors associated with low fertility can facilitate the development of effective strategies to enhance reproductive performance on dairy farms.
Traditionally, the uterus has been considered free of microbes, but recent advancements in next-generation sequencing technology have revealed the presence of a "uterine microbiota" specific to the uterine environment. Numerous studies on uterine microbiota have been conducted in humans, demonstrating a correlation between fertility and the diversity of the microbial population in the uterus.
Could this knowledge be extended to reared animals?
To explore this possibility, Mr. Takuya Yagisawa, Section Chief at the Hokkaido Agriculture Mutual Aid Association, Japan, and Dr. Jumpei Uchiyama, Associate Professor at Okayama University, Japan, collaborated with their research teams to investigate the relationship between low fertility and uterine microbiota in dairy cows.
In dairy farming, a voluntary waiting period (VWP) is observed between calving and the first artificial insemination (AI) to allow for uterine involution and prepare for the next pregnancy. While the uterine microbiota has been studied in terms of postpartum uterine inflammation in cows, its connection with fertility after the VWP remains poorly understood. This is where the new study comes into play.
The research team consisted of Iyo Takemura-Uchiyama (Postdoctoral Fellow, Okayama University), Shun Ando (Assistant Section Chief, Hokkaido Agriculture Mutual Aid Association), Osamu Ichii (Associate Professor, Hokkaido University), Hironobu Murakami (Associate Professor, Azabu University), Osamu Matsushita (Professor, Okayama University), and Seiji Katagiri (Professor, Hokkaido University). They employed 16S rRNA gene amplicon sequencing to identify different types of bacteria present in the uterine tissues they sampled. Subsequently, microbiota data from 69 cows on four commercial dairy farms were analyzed. The researchers compared the microbial diversity among the samples based on factors such as farm, housing style, and feeding management practices. Additionally, they correlated the uterine microbiota data with parity (number of deliveries) and the frequency of artificial insemination (AI) to conception for each cow.
The study's findings were published in Microbiology Spectrum on April 26, 2023.
The results revealed significant differences in farm management-related factors (such as housing style and feeding management) among the four farms. Notably, these differences were associated with variations in uterine microbiota. However, no significant differences were observed regarding the frequency of AI in relation to conception and parity.
To eliminate the potential influence of variations in farm management practices across different farms, the researchers further investigated the correlation between fertility and uterine microbiota using data from 31 cows on a single dairy farm. Cows that achieved conception within three AI attempts were categorized as having normal fertility, while cows requiring more than three AI attempts were considered to have low fertility.
The findings of this study strongly indicate that the uterine microbiota undergoes changes in relation to the fertility of cows. There is a correlation between microbial diversity and the frequency of artificial insemination (AI) required for conception, and the bacterial taxon Arcobacter exhibited increased compositional rates. Additionally, the bacterial associations differed between cows with normal fertility and those with low fertility.
These results suggest that variations between different farms can significantly influence the diversity of uterine microbiota in dairy cows. Furthermore, the composition of uterine microbiota changes in relation to the fertility of cows.
Dr. Uchiyama emphasizes the practical implications of their research, stating, "We hope that further studies will establish uterine microbiome testing as a novel approach for diagnosing the causes of low fertility and contribute to enhanced reproductive management in animal husbandry."
Providing further insights into their research, Mr. Yagisawa explains, "We utilized a metataxonomic approach to analyze the uterine microbiota using endometrial tissue biopsy samples from dairy cows."
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