Metritis diagnosis

By Dr. Caio Figueiredo, Veterinary Medicine Extension

Metritis is a uterine disease associated with severe detrimental impacts on productive and reproductive performance, as well as animal mortality and welfare. Although reports and studies related to metritis date back to the early 1980’s, the clinical signs that defined the disease were extremely variable. In 2006, a paper published within the journal Theriogenology proposed new definitions for uterine diseases in cattle, including metritis, endometritis, and pyometra (Sheldon et al., 2006). Currently, the most common method for metritis diagnosis in dairy cows is visual evaluation of vaginal discharge and characterization according to color, viscosity, and odor.

The 2006 article has become the most cited source for defining uterine diseases, particularly metritis, and has helped standardize further studies related to uterine diseases. However, despite improvements in case definitions for metritis, a recent review indicated that large variations related to vaginal discharge viscosity (purulent, mucopurulent, or watery) that defines metritis still exist (Garzon et al., 2022). The inconsistencies in defining metritis are not restricted to the research realm. A study that evaluated metritis diagnosis practices in 45 California dairies reported that metritis diagnosis is inconsistent across dairies as well (Espadamala et al., 2018). Although it sounds insignificant to be assertive when characterizing viscosity of vaginal discharge, many problems arise from inconsistent diagnosis of metritis in dairy herds. For instance, inconsistent diagnosis decreases the likelihood of identifying positive cases, may delay onset of antibiotic treatment (see below), and increases the amount of milk loss that is unaccounted for within the herd, potentially underestimating economic losses.

Economic models using varying levels of consistency in the diagnosis of metritis have been used to evaluate the impact of misclassification of metritis on milk production (McCarthy and Overton, 2018). In that study, the inconsistency in metritis diagnosis caused up to 330,256 kg of unaccounted milk loss (Figure 1). Unaccounted milk loss represents the underestimation of metritis impacts at the herd level and prevents the possibility of optimizing protocols without a closer look into health evaluation practices. At this point, it is clear that establishing a criteria for metritis definition based on changes in performance indicators is necessary. A recent study presented at the American Dairy Science Association conference addressed this problem (Figueiredo et al., 2022). In that study, vaginal discharge was scored into 5 different groups (1 = clear mucus/lochia, 2 = clear mucus with flecks of pus, 3 = mucopurulent with < 50% of pus, 4 = mucopurulent with ≥ 50% of pus or reddish/brownish mucous discharge not fetid, and 5 = watery, reddish/brownish, and fetid discharge; Figure 2). Reproductive performance, mortality, and milk production were compared among the 5 groups of cows. Return to estrous cyclicity by 67 days in milk (DIM) and risk of receiving a first service were reduced for cows with discharge 5 (70.7 and 85.5%) compared with 2 (80.5 and 90.1%), 3 (78.9 and 90.1%), and 4 (79.6 and 91.7%), but not 1 (79.0 and 89.3%). Although discharge was not associated with proportion of pregnant cows and pregnancy loss after first service, the proportion of cows pregnant by 300 DIM was reduced for cows with discharge 5 (65.1%) compared with 2 (70.2%), 3 (72.7%), 4 (73.9%), but similar for 1 (69.1%). Median days to pregnancy according to vaginal discharge group 1 to 5 were 118, 117, 123, 130, and 148, respectively. Proportion of cows removed from the herd within 300 DIM was greater for cows with discharge 5 (22.1%) compared with 1 (17.2%), 2 (15.4%), 3 (13.9%), and 4 (15.3%). Risk of leaving the herd did not differ among cows with discharge
1 to 4. Milk production was different according to vaginal discharge group. Although milk production did not
differ among primiparous cows, milk production for multiparous cows with discharge 5 was smaller compared
with discharge 1 (-7.1 kg/d), 2 (-7.4 kg/d), 3 (-4.8 kg/d), and 4 (-3.6 kg/d) in the first 3 months of lactation. These
results support the need to restrict the definition of metritis in dairy cows with vaginal discharge 5 instead of
vaginal discharge 5 and 4 as previously postulated.

Figure 1. Second test 305-d mature-equivalent milk projection (2nd 305ME) for all cows, cows classified as no metritis recorded, mild metritis, or severe metritis for the true severity (TrS) model and misclassified in the inconsistent recording (IR) and poor recording (PR) models. Negative numbers above the mild metritis and severe metritis columns for each model represent the associated milk loss (kg) for cows with mild or severe metritis.

Figure 2. Representation of vaginal discharge characteristics according to scores.

References

1. Espadamala, A., R. Pereira, P. Pallarés, et al. 2018. Metritis diagnosis and treatment practices in 45 dairy farms in California. J. Dairy Sci. 101:9608-9616.
2. Figueiredo, C. C., V. R. Merenda, E. B. de Oliveira, et al. 2022. Redefining metritis in dairy cows based on health and performance indicators associated with vaginal discharge score. Vol. 105 (Suppl. 1). J. Dairy Sic., American Dairy Science Association; Kansas City, MO.
3. Garzon, A., G. Habing, F. Lima, N. Silva-Del-Rio, et al. 2022. Defining clinical diagnosis and treatment of puerperal metritis in dairy cows: A scoping review. J. Dairy Sci. 105:3440-3452.
4. McCarthy, M. M. and M. W. Overton. 2018. Short communication: Model for metritis severity predicts that disease misclassification underestimates projected milk production losses. J. Dairy Sci. 101:5434-5438.
5. Sheldon, I. M., G. S. Lewis, S. LeBlanc, et al. 2006. Defining postpartum uterine disease in cattle. Theriogenology 65:1516-1530