The relationship between endometrial cytology during estrous cycle and cutoff points for the diagnosis of subclinical endometritis in grazing dairy cows

Abstract

The objectives of this study were to assess the effect of the stage of estrous cycle on the percentage of endometrial polymorphonuclear cells (PMN) obtained by cytobrush to determine cutoff values for the diagnosis of subclinical endometritis under pastoral conditions, to measure the prevalence of subclinical endometritis 21 to 62d in milk (DIM), and to evaluate the effect of subclinical endometritis on reproductive performance in grazing dairy cows. The first experiment was conducted on a commercial dairy farm in Buenos Aires province (Argentina), where 17 postpartum cyclic dairy cows without clinical endometritis were selected and synchronized by Ovsynch protocol. Endometrial cytology (cytobrush technique) and blood (tail vessels) samples were obtained on d0, 4, 11, and 18 of the estrous cycle (corresponding to estrus, metestrus, diestrus, and proestrus, respectively) and used for measuring percentage of PMN and P4 concentration, respectively. The percentage of PMN was determined 3times by blinded count by 2 operators. Data were analyzed with PROC MIXED, PROC GENMOD, and PROC FREQ from SAS 9.1. The percentage of PMN did not vary with the stage of the estrous cycle. In addition, PMN counts were below any of the reported thresholds in this study (4%) for most of the cows. Therefore, the risk for false positive test results as a consequence of physiological changes in the counts of PMN during estrous cycle is low. The second experiment was conducted on 4 commercial dairy farms in Buenos Aires province (Argentina), where lactating Holstein dairy cows (n=418) 21 to 62 DIM without clinical endometritis were studied. Samples of endometrial cytology were collected with the cytobrush technique. Data were analyzed with receiver operator characteristic curves with Sigmaplot 10.0, and with PROC GLIMMIX, PROC PHREG, and PROC LIFETEST from SAS 9.1. Cutoff values for the diagnosis of subclinical endometritis in grazing dairy cows are 8% PMN for 21 to 33 DIM, 6% PMN for 34 to 47 DIM, 4% PMN for 48 to 62 DIM, and overall 5% PMN for 21 to 62 DIM; the prevalence of subclinical endometritis 21 to 62 DIM was 17%. Finally, subclinical endometritis diagnosed at 21 to 62 DIM decreases the hazard for pregnancy (hazard ratio=0.668; 95% confidence interval=0.492-0.909) and increases the calving to conception interval by d30 compared with normal cows (median 95% confidence interval=133 vs. 93, respectively).

Agreement between postmortem endometrial cytology, biopsy and bacteriology in culled dairy cows

“…On the other hand, the cut-off point of % PMN established for positive cytology may have influenced the agreement between the two techniques, since it was found that about 15% of healthy uteri diagnosed by histology were classified with positive cytology. As previously reported by Madoz et al (2013), in the present study, cytology outputs were not influenced by the phase of the estrus cycle at the time of diagnosis. However, by using biopsy, a higher degree of inflammatory infiltration could be detected during the follicular phase of the cycle.…”

The usage of insemination casing in collecting the cytological material from the cow’s uterus in order to reduce the method’s invasiveness

“…According to numerous authors the endometritis is to be suspected in cows with the PMNs percentage exceeding 4-5% on 45-50 day after parturition (Barański et al, 2012;Kasimanickam et al, 2004;Madoz et al, 2014). Madoz et al (2013) stress that the percentage of PMNs does not change in the estrus period cycle in healthy cows. It is confirmed by the results obtained in the authors' investigations in which small differences between the neutrophils percentage in cows in heat and those outside the estrus period were not statistically significant (p > 0.05).…”

Agreement among bacteriological findings, vaginal discharges, and endometrial cytology for endometritis detection in postpartum beef cows.

“…Endometrial cytological samples were collected from cows by using a modified sterile Cytobrush Plus GT (Medscand Medical, Germany) (Madoz et al, 2013). The handle was shortened to 2 cm and made thread-like to enable insertion into a stainless steel rod (artificial insemination AI gun 65 cm in length, 4 mm outside diameter).…”