Abstract
Clinical endometritis (CE) and subclinical endometritis (SCE) are diseases that affect dairy cows during the puerperium, causing negative effects on the animals' milk production and fertility. The objective of this study was to assess the main bacteria related to cases of CE and SCE from uterine samples of dairy cows in Brazilian herds. Selective and differential media were used for isolation of aerobic and anaerobic bacteria and further MALDI-TOF mass spectrometry (MS) identification. A total of 279 lactating dairy cows with 28 to 33 d in milk from 6 commercial farms were evaluated. Initially, cows were classified in 3 groups: cytologic healthy cows (n = 161), cows with CE (n = 83), and cows with SCE (n = 35). Healthy animals presented 97 species, followed by the CE group with 53 identified species, and SCE cows presented only 21 bacterial species. We found a significantly higher isolation rate of Trueperella pyogenes in CE (26.5%) cows compared with healthy and SCE cows. Some anaerobic species were exclusively isolated from the CE group, even though they presented lower frequency. Interestingly, 18.1% of samples from CE cows and 40% of SCE cows were negative to bacterial isolation. Despite the use of culture-dependent methods instead of molecular methods, the present study enabled the identification of a complex community of 127 different species from 48 genera, composed of aerobic and anaerobic bacterial species among the 3 different animal groups. The method of sample collection, culture, and identification by MALDI-TOF MS were essential for the success of the analyses.
Highlights
Endometritis is one of the most important causes of infertility in dairy herds
Healthy animals presented numerically greater richness (97 identified species) followed by the clinical endometritis (CE) group (53 identified species), whereas only 21 bacterial species were identified among the subclinical endometritis (SCE) group
Most of the species from the SCE group are shared between healthy animals and those with CE (Figure 1)
Summary
Endometritis is one of the most important causes of infertility in dairy herds. Its effects on dairy farms include the costs related to the treatment of the affected animals, milk discard, culling, decrease in milk production, and worsened fertility of the affected cows (Gilbert et al, 2005; LeBlanc, 2008; Paiano et al, 2019, 2020a,b).Endometritis is the inflammation of the endometrium, the innermost lining of the uterus, being subdivided into clinical endometritis (CE) and subclinical endometritis (SCE; Sheldon et al, 2006). Subclinical endometritis is characterized by an increased proportion of PMN in the endometrium in the absence of clinical disease (Gilbert et al, 2005). Previous studies have reported that the main bacterial species associated with endometritis in dairy cows are Trueperella pyogenes, Escherichia coli, and Fusobacterium necrophorum (Williams et al, 2005; Sheldon et al, 2010; Machado et al, 2012; Bicalho et al, 2017a; Bogado Pascottini et al, 2021). When the studies involve culture and identification of isolated bacteria, this can Paiano et al.: ENDOMETRITIS IN DAIRY COWS be conducted using traditional biochemical methods or more modern techniques such as MALDI-TOF MS (Ballas et al, 2021), sequencing of 16S rRNA gene (Bogado Pascottini et al, 2020), or Fourier-transform infrared (Prunner et al, 2014; Wagener et al, 2014). Metagenomic analyses are conducted via 16S rRNA gene profiling by high-throughput sequencing (Bicalho et al, 2017b; Wang et al, 2018)
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