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The importance of acute puerperal metritis (APM) and an efficacious treatment has been outlined by many authors (Benzaquen et al., 2007; Drillich et al., 2007; Overton and Fetrow 2008). However, there is a lack of science-based evidence for the diagnostic values of methods to identify cows with APM.
Therefore, the objective of this thesis was to investigate how relevant research publications address the validity of diagnostic methods for APM, to determine the test characteristics of an evaluation of vaginal discharge by human senses and an electronic device and to compare two monitoring and treatment strategies of fresh cows for APM.
In the first study, a literature search was conducted in four relevant scientific Journals utilizing the Sciencedirect database. Studies were checked for definitions of possible findings, thresholds, and test characteristics of the diagnostic methods used to identify a cow with APM.On average 2.5 ± 1.75 diagnostic methods were used in a study. References to support the use of the diagnostic methods were provided in 10 of 48 articles (20.8%). Thresholds for diagnostic tests and test characteristics were mentioned in 6 and 3 of the 48 articles, respectively. Based on this systematic review of 48 research papers the evidence supporting the use of the diagnostic methods to identify cows with APM has either been not reported or is weak. In conclusion, the reporting of diagnostic methods to identify cows with APM needs to be improved and further research is necessary to improve diagnostic performance of the methods employed.
The objective of the second part of my thesis was to evaluate the reliability of a sensory assessment for color, smell, and viscosity of vaginal discharge from healthy cows and cows with APM. A total of 15 investigators evaluated 6 vaginal discharge samples 10 times each. Subsequently the investigators rated the health status of the cows and the diagnostic value of color, smell, and viscosity. In a final questionnaire, the investigators estimated their ability to diagnose APM correctly and the influence of experience. Reliability was tested using Cohen’s kappa (К). Our study revealed slight to moderate reliabilities concerning the assessment of vaginal discharge.
Overall interobserver reliability for color, smell, and viscosity was К= 0.15, 0.27 and 0.44, respectively. Overall intraobserver reliability for color, smell and viscosity were К=0.35, 0.39 and 0.6, respectively. The overall personal expertise to detect cows suffering from APM correctly as such was estimated to be 59%. Our study shows that the sensorial assessment of color, smell, and viscosity of vaginal discharge in cows postpartum is subjective.
Therefore, the third part of this thesis involves the use of an electronic nose device to test whether the diagnosis of APM can be refined by technical means. This part includes the definition of test characteristics of an evaluation of odor from vaginal discharge (VD) of cows in the first 10 d postpartum conducted by olfactory cognition and an electronic device, respectively. In experiment 1, 16 investigators (9 veterinary students and 7 licensed veterinarians) evaluated 5 VD samples each on 10 different days. The kappa test revealed an agreement between investigators (interobserver) of κ = 0.43. Mean agreement within observers (intraobserver) was κ = 0.52. In experiment 2, the repeatability of an electronic device (DiagNose; C-it, Zutphen, the Netherlands) was tested. Therefore, 5 samples of VD from 5 cows were evaluated 10 times each. The repeatability was 0.97, determined by Cronbach’s α. In experiment 3, 20 samples collected from healthy cows and 20 of cows with acute puerperal metritis were evaluated by the 16 investigators and the DiagNose using a dichotomous scale (1 = cow with acute puerperal metritis; 0 = healthy cow). Sensitivity and specificity of olfactory evaluation was 75.0 and 60.1% compared with 92.0 and 100%, respectively, for the electronic nose device.
The study confirms a considerable subjectivity of the human nose concerning the classification into healthy and sick animals based on the assessment of vaginal discharge. The repeatability of the electronic nose was higher. In conclusion, the DiagNose system, although imperfect, is a reasonable tool to improve odor assessment of VD. Further research is warranted to adapt such electronic devices to practical on-farm screening tools.
In the forth part of my thesis, two strategies for screening and subsequent treatment of acute puerperal metritis (APM) in dairy cows have been compared. Therefore, a study with 79 cows, having APM and 114 healthy control cows was conducted. Cows with APM were divided into two groups (treated n= 67 cows, not treated n= 12 cows). The treated animals were further subdivided into two groups (treated between D1-4, n=12 and treated between D5-10, n= 55).
The results of this study did not show any significant differences in cure rates, milk yield, serum haptoglobin concentrations on DIM 2, 5 and 10 and subsequent uterine health (DIM 21 to 27). Considering this study as a proof of concept study, we conclude that there might not be a negative impact following a screening and treatment protocol beginning at DIM 5 and leaving early APM cows untreated. This hypothesis needs to be confirmed by a larger field study.
Overall, in the course of the four studies a systematic review of current literature considering cows with APM revealed that the evidence of diagnostic methods to identify cows with APM is weak. My second study was implemented to evaluate the diagnostic performance of color, smell and viscosity of cows with and without APM evaluated by human senses. The third part involves the use of an electronic nose device, revealing a better diagnostic performance than by sensorial assessment of VD. The aim of the forth part of this theses was to find out the most efficient strategy to detect cows, suffering from APM and cope with the prudent antibiotic drug use. The results show that a delayed treatment beginning at DIM 5 can lead to a considerable reduction of antibiotic drug use in cows with APM.