Assessing Long-Term Changes in Endometrial Morphology and Functionality in Dairy Cows With Metritis

This study evaluated the long-term impact of metritis on endometrial morphology and functionality in dairy cows. Postpartum Holstein cows (n = 107) were enrolled in a cohort study at the University of Idaho Dairy Center. Metritis was diagnosed using a Metricheck device within 12 days in milk (DIM) based on the presence of fetid, watery, reddish-brown vaginal discharge (VD). Cows diagnosed with metritis (MET; n = 9) were treated with ceftiofur crystalline free acid and paired with cows without metritis (NoMET; n = 9) of similar parity and DIM. Ovulation was synchronized using a Double Ovsynch protocol starting at 35 DIM, and ovulation was confirmed by ultrasonography. To eliminate confounding effects of semen or conceptus-derived signals, cows were not inseminated. Six days after ovulation (68-75 DIM), endometrial biopsy and cytology samples were collected. Endometrial morphology was assessed by histological evaluation of haematoxylin and eosin-stained sections. Endometrial transcriptomic profiles were determined by RNA sequencing from tissues collected via biopsy, and uterine fluid collected during cytology was analysed using metabolomic profiling. Differential gene expression was assessed using DESeq2, and metabolomic differences were evaluated using partial least squares discriminant analysis and PERMANOVA. Cows with metritis exhibited a numerically greater prevalence of periglandular fibrosis (63%; 95% Exact Binomial Confidence Interval [CI] = 25-92) compared with NoMET cows (44%; 95% CI = 14-79). Transcriptomic analysis identified 17 differentially expressed genes (FDR ≤ 0.10; |log2 fold change| > 1), including upregulation of genes associated with tissue repair in MET cows. No differences were detected in uterine fluid metabolomic profiles between groups. In conclusion, metritis was associated with persistent alterations in endometrial morphology and gene expression that were detectable months after clinical resolution, although these changes were not reflected in the uterine fluid metabolome.