Gross abnormalities, bacteriology and histological lesions of uteri of dairy cows failing to conceive or maintain pregnancy

AIM: To describe the gross pathology, bacteriology and histopathology of the reproductive tracts of dairy cows that failed to conceive or maintain pregnancy. METHODS: The reproductive tracts of 105 cows that were not pregnant at the end of the seasonal breeding programme were retrieved following slaughter. The tracts were examined grossly, both horns of the uterine lumen were swabbed for bacteriology, and tissue was collected from each horn and the body of the uterus for histopathology. Grossly enlarged uteri and tracts containing purulent vaginal content were excluded. Histopathology was performed on three sections of uterine tissue from each of three cows in which no gross pathological changes were detected and from which no bacteria were isolated, from three cows in which no gross pathology was detected but from which bacteria were isolated, and from three cows in which gross pathological changes were detected but from which no bacteria were isolated. RESULTS: Thirty-six (34%) cows had one or more gross lesions which involved the ovary, uterine tube, uterus or vagina. Bacteria were isolated from the uteri of 22 (21%) cows. Isolates included Arcanobacterium pyogenes (n = 1), Escherichia coli (n = 1), Fusobacterium spp (n = 1), Haemophilus somnus (n = 5), Streptococcus acidominimus (n = 12), S. bovis (n = 2), S. uberis (n = 1) and S. salivarious (n = 1). In only five cows were both gross pathology and bacteria detected. There was no relationship between the isolation of bacteria and the diagnosis of gross pathology of the uterus. There were no differences in the degree of histopathological changes in the uteri from the three groups of cows examined, and lesions present were minor. CONCLUSIONS: Gross pathological changes and intra-uterine bacteria were found in 34% and 20% of cows, respectively, but the correlation between the two was poor. Histopathological changes were unremarkable, suggesting the bacteriological findings were coincidental, that causative agents of infertility were not present at the time of examination, or that unrelated causes such as nutritional anoestrus may have been responsible for the failure of some cows to conceive.