The relationship between endometritis and cystic ovarian disease (COD)
is still unclear in Japanese Black cattle. Endometritis is classified into
clinical endometritis (CE) and subclinical endometritis (SE). The objective
of this study was to clarify the interaction between postpartum endometritis
(CE and SE) and COD in Japanese Black cattle. Twenty-six suckled cows with
COD (COD group) and 16 suckled cows with cyclical ovarian activity (CA
group) were submitted for the experiment. Uterine conditions of cows were
classified into three groups (normal, CE, and SE) with vaginal mucus test and
endometrial cytology. The combined data of CE and SE were represented as data
for total endometritis (EMT total). The prevalence of EMT total in the COD group
(42.3 %,
Cystic ovarian disease (COD) and endometritis are major reproductive
problems in both dairy and beef cattle during the postpartum period,
resulting in a prolonged open period (Garverick, 1997; Gobikrushanth et al.,
2016). According to statistical information from the Ministry of Agriculture,
Forestry and Fisheries of Japan in 2018
(
In dairy cattle, endometritis can be classified into clinical endometritis (CE) and subclinical endometritis (SE) by vaginal mucus test and endometrial cytology (Sheldon et al., 2006; Pleticha et al., 2009; Senosy et al., 2009; Barański et al., 2013). Especially endometrial cytology is important for the diagnosis of SE (Polat et al., 2015; Pothmann et al., 2015). Endometrial cytology performed with the cytobrush (Kasimanickam et al., 2005; Barlund et al., 2008; Senosy et al., 2011) and uterine lavage techniques (Kasimanickam et al., 2005; Santos et al., 2009; Galvão et al., 2011; Cocchia et al., 2012) has been used to determine the PMN %. There is no study that evaluated the relationship between endometritis and COD with the vaginal mucus test by Metricheck and cytobrush method in Japanese Black cattle. Transrectal ultrasonography (US) has been widely accepted for reproductive examination. Although the diagnosis of SE by endometrial cytology and US has been reported in dairy cattle (Kasimanickam et al., 2004), the relationship between these methods has not been studied in Japanese Black cattle. Therefore, the incidence rate of endometritis with COD and efficiency of US for endometritis diagnosis should be examined in Japanese Black cattle.
In beef cattle, uterine involution is completed at 37.7–56.0 DPP (days postpartum) (Noakes et al., 2009). Uterine inflammation reaches a peak at 1–3 DPP and the prevalence of uterine disease decreased gradually with the extension of postpartum period (Sheldon et al., 2009). In Japanese Black cattle, correlation between uterine condition and DPP in Japanese Black cattle with COD has not been studied yet.
The objective of this study is to reveal the interaction between postpartum endometritis (CE and SE) and COD in Japanese Black cattle with vaginal mucus test and endometrial cytology. Diagnostic accuracy of US for endometritis was also examined.
Animal handling and experimental procedures were carried out by following the
Guidelines for Proper Conduct of Animal Experiments by the Science Council of
Japan (
A field trial was conducted during April 2014 to August 2016 on the 15
commercial farms in Okuizumo town, Shimane Prefecture, Japan. Herds of 1 to
100 cows were selected for the study. The cows with COD (COD group) were
selected from cows that were requested for reproductive therapy because of
anestrous after 40 DPP having a cystic structure larger than 25
All cows received rectal palpation and transrectal US using a real-time
B-mode scanner with a 7.5
The vaginal mucus was collected by Metricheck in a similar manner as in
previous studies (Pleticha et al., 2009; Senosy et al., 2009). After the
cytobrush assessment, the Metricheck device was inserted into the vagina. The cup of
the device was inserted to external uterine orifice and subsequently the
opposite side of the device was elevated slightly to fill the cup with
vaginal mucus. Then the device was withdrawn gently from the vagina. Vaginal
mucus was scored according to previous studies (Williams et al., 2005;
Sheldon et al., 2006; Senosy et al., 2009) on a 0 to 3 scale (score 0 represents clear or translucent mucus; score 1 represents mucus containing flecks of white or
off-white pus; score 2 represents discharge containing
Endometrial cytology by the cytobrush method was performed according to previous
studies (Kasimanickam et al., 2005; Sheldon et al., 2006; Senosy et al.,
2011). Briefly, the rod of the cytobrush, made from stainless steel (51
Pathological conditions of the uterus were allocated into three groups by scoring vaginal mucus (Sheldon et al., 2006) and PMN % (Barlund et al., 2008; Gobikrushanth et al., 2016). In this study, the cutoff value of PMN % was set at 8 % in accordance with previous reports which recommended 8 PMN % as a good diagnostic cutoff value to discriminate between normal and endometritis in dairy cattle (Barlund et al., 2008) and beef cattle (Salah and Yimer, 2017). A cow with a mucosal score less than 2 and PMN % less than 8 % was considered normal. A cow with a mucosal score above 2 was considered CE, whereas a cow with a mucosal score less than 2 and PMN % above 8 % was considered SE.
Morbidity with endometritis was analyzed by a one-side test with Fisher's
exact test. PMN % and diameters of largest follicle, cervix, and uterus at
the base of the horn among groups were analyzed with analysis of variance
and Tukey's test. Differences with
Prevalence of clinical endometritis (CE) and subclinical endometritis (SE) in Japanese Black cattle diagnosed with vaginal mucus test and endometrial cytology. In parentheses is the number of cows.
Diameter of uterine horn and cervix measured with transrectal US and PMN % assessed with endometrial cytology in Japanese Black cattle.
The cows were allocated into 40–60 and 61–295 DPP groups, and the table shows the proportion
of cows with normal uterus, CE and SE in COD group, and CA group in Table 1.
The proportions of normal uterus, CE, and SE did not differ statistically
between CA and COD groups at both 40–60 and 61–295 DPP. The combined data of
CE and SE were represented as data for total endometritis (EMT total) in this
study. The prevalence of EMT total of the COD group (42.3 %,
In dairy cattle, some studies reported the relationship between endometritis
and COD in dairy cattle (Kesler and Garverick, 1982; Bosu and Peter, 1987;
Kim et al., 2005); however, research into postpartum dairy cattle cannot
exclude the effects of milk production. High milk production and the related
negative energy balance increase the risks of endometritis (Opsomer and
Kruif, 2009; Cheong et al., 2011) and ovarian dysfunction (Opsomer et al.,
2006). In Japanese Black cattle, the prevalence of EMT total in the COD group
was significantly higher than that of the CA group in this study. The mean
PMN % in the COD group was also higher than that in the CA group at 40–60 DPP.
This is the first report that reveals that Japanese Black cattle with COD
carry a high risk for endometritis (CE and SE) at 40–60 DPP. The finding
in Japanese Black cattle in the present study also suggests that not high
milk production but physiological postpartum endometritis can contribute to
the development of COD in the early postpartum period in cows because the
effects by lactation in the postpartum period are smaller in Japanese Black cattle than
in dairy cattle (Shingu et al., 2002). These results are similar to
previous studies which reported the relationship between endometritis and COD in
dairy cattle (Kesler and Garverick, 1982; Bosu and Peter, 1987; Kim et al.,
2005). Several reasons for the relationship between COD and endometritis
have been described in dairy cattle. Ovulation is an important factor for
the incidence of COD, and endometritis is associated with failure of
ovulation (Opsomer et al., 2000; Sheldon et al., 2002).
Our results differ with a previous report that the prevalence of endometritis at 25 DPP had no effect on the existence of follicular cysts at 35 and 65 DPP in dairy cattle (Gobikrushanth et al., 2016). This might be due to the difference in research period of endometritis. Though Gobikrushanth et al. (2016) mentioned that the prevalence of endometritis was 71.4 % at 25 DPP, postpartum uterine recovery was not completed at 25 DPP in dairy cattle (Noakes et al., 2009) in which the uterus had endometritis physiologically (Sheldon et al., 2009).
One possible reason for the incidence of endometritis in cow with COD is dysfunction of the estrus cycle. In normal healthy cows, the uterus should be sterile by 6–8 weeks postpartum (Sheldon and Dobson, 2004). The occurrence of the estrus cycle after calving seems to be important for uterine involution and clearance (Noakes et al., 2009). However, in this study the prevalence of EMT total and mean PMN % in Japanese Black cattle with COD at 40–60 DPP was higher than that at 61–295 DPP. And there was no significant difference between COD and CA groups in PMN % at 61–295 DPP. If COD gives rise to endometritis, this uneven distribution of endometritis on DPP should not be observed. These results indicate that COD at 61–295 DPP has no effect on the occurrence of endometritis. Rather, the presence of follicular cysts may enhance uterine clearance by producing estradiol (Yoshioka et al., 1996), acting as a stimulator of the hormonal immune system (Grossman, 1985). Thus, it is conceivable that COD was not a cause of endometritis. As numerous factors are known to induce COD (Vanholder et al., 2006), COD at 61–295 DPP may be induced by the other reasons rather than endometritis.
In this study, however, the prevalence of EMT total did not differ between the COD group and CA group at neither 40–60 nor 61–295 DPP. The limitations of
the diagnostic method for endometritis might have influenced the results. It
has been reported that the distribution of PMN throughout the endometrium is
different for each pathogen (Bonnett et al., 1991). And the results of
PMN % by the cytobrush method increased with the presence of
Endometrial thicknesses at both 40–60 and 61–295 DPP were greater in the COD group in this study, and these results could be explained by the fact that estrogen induces edema in the endometrium and increases endometrial thickness (Sugiura et al., 2018). However, in the present study, we did not evaluate steroid hormones. In a further study, we should examine the levels of steroid hormones and the relationship between endometritis, COD, and steroid hormones. Neither CE nor SE had an effect on the diameter of uterus or cervix in this study. Moreover, the prevalence of uterine fluid by transrectal US disagreed with the result of vaginal mucus test by Metricheck and endometrial cytology by cytobrush. Other specific findings were not observed by transrectal US. Though it was reported that existence of uterine fluid by US was suitable for diagnosis of SE as endometrial cytology in dairy cattle (Kasimanickam et al., 2004), this study revealed that diagnosis only by US was not able to detect CE nor SE in Japanese Black cattle. Especially in a cow with COD, it is difficult to diagnose whether inflammation or estrogen is the cause for uterine fluid. As shown in several previous reports (Sheldon et al., 2006; Pleticha et al., 2009), vaginal mucus test and endometrial cytology are essential for the diagnosis of endometritis in cow with COD. However, vaginal mucus test is not a common diagnosis method for veterinarians in Japan. The cytobrush method in cows has been established during the last decade (Kasimanickam et al., 2004, 2005; Barlund et al., 2008), and few veterinarians use the cytobrush method to detect endometritis. Considering the risk for endometritis in cows with COD, vaginal mucus test and endometrial cytology should be carried out as a general diagnosis method at 40–60 DPP in Japanese Black cattle.
In conclusion, Japanese Black cattle with COD have a potential implication for endometritis at 40–60 DPP compared to the cows with a normal ovarian cycle. Thus, we recommend vaginal mucus test and the cytobrush method for examining endometritis when COD is diagnosed. Especially endometrial cytology is essential to diagnose SE in Japanese Black cattle.
The original data are available upon request to the corresponding author.
All authors contributed to the work described in the article and take responsibility for it. NY, RN, YG, and MH as co-authors made a significant contribution to the conception and design of the experiments and the analysis and interpretation of the data.
The authors declare that they have no conflict of interest.
We would like to thank owners and crews of the farms for their outstanding cooperation. We thank Takeshi Osawa of Miyazaki University for technical advice on the cytobrush method. We also thank Shambhu Shah of Tribhuvan University for English proofreading of the manuscript and Jun Kawase for support with statistical analysis.
This paper was edited by Manfred Mielenz and reviewed by Frank Becker and one anonymous referee.