Responses to rectal and uterine palpation for assessment of visceral pain associated with metritis in dairy cows

Abstract Text: Metritis is a common disease in dairy cattle following calving, but to our knowledge no work has assessed the associated pain. A common method of assessing pain in human and veterinary medicine is through responses during tissue palpation. The objective of this study was to evaluate visceral pain responses in cows with clinical signs of metritis during rectal and uterine palpation. A total of 62 Holstein dairy cows (mean±SD parity 3±1.5) were subjected to systematic health checks starting day 3 after parturition and continuing every 3rd day for 21 days. Cows were scored for vaginal discharge (0 to 4); 13 cows showed a discharge score ≥ 2 during at least one health check; these cows were classified as metritic. A matched (by parity and DIM at diagnosis) sample of 13 cows were classified as ‘healthy’. Cows showing any other signs of disease (including mastitis, ketosis and lameness) were not included in the study. Behavioral and physiological responses during palpation were recorded using video and heart rate monitors. The effects of health status (healthy versus metritic) and exam method (rectal versus uterine palpation) were tested using MIXED model. Back arch (cm²) on the day of diagnosis was higher for metritic cows than healthy cows (P<0.01), with no significant effect of palpation method or interaction. During rectal palpation back arch averaged (±S.E.) 28±2.3cm² for metritic versus 18±2.3cm² for healthy cows and during the uterine palpation back arch averaged 31±2.3 versus 19±2.3cm², respectively. Standard deviation between normal to normal inter beat intervals (SDNN) and root of the mean square of successive differences (RMSSD) were log transformed prior to analysis. Both measures varied in response to exam method (P<0.05), but not health status or interaction. The SDNN during rectal palpation averaged (±S.E.) 2.7±0.16, compared to the uterine palpation 2.1±0.16. Similarly, RMSSD was 1.8±0.14 during the rectal palpation, but decreased in the uterine palpation to 1.4±0.14. The heart rate variation measures indicate that both healthy and metritic cows found uterine palpation more stressful than rectal palpation. The back arch results indicate that metritic cows are more sensitive to palpation (of both methods) than are healthy cows. These results also suggest that these types of veterinary exam may be used to identify cows that are experiencing pain associated with metritis, and thus maybe be useful in deciding which animals will benefit from treatment with analgesics.

Keywords: visceral pain, metritis, pain response