Cow-level risk factors for reproductive tract disease diagnosed by 2 methods in pasture-grazed dairy cattle in Ireland

摘要

The cow-side diagnosis of reproductive tract disease(RTD) involves identifying the presence of purulentvaginal discharge (PVD) and ultrasonographic endometritis(UE). The objectives of our study were toobtain prevalence estimates for RTD diagnosed by 2methods (PVD and UE scoring) and to investigate therisk factors for increased probability of RTD if thesemethods are used in isolation or in combination. Ourretrospective observational cohort study tested the hypothesisthat RTD assessed by 2 methods would havesimilar risk factors, and that those would be mainlycow- and calving-related factors. We analyzed datafrom 5,049 pre-breeding examinations (PBE) from2,460 spring-calved cows on 8 farms between 2014 and2018. Cow-related details assessed were days in milkat PBE, breed, lactation number, dry period length,body condition score at calving and PBE, 305-d milkyield, predicted transmitting ability for production andfertility, the presence of a corpus luteum at PBE, andpositive diagnosis the previous year. Calving details assessedwere type of sire, calf sex, twinning, stillbirth,calving difficulty score, and retained fetal membranes.We conducted statistical analyses using 4 multivariablelogistic regression models to identify the risk of RTDdiagnosed by (1) PVD in isolation, (2) UE in isolation,(3) the presence of either PVD or UE; and (4) the presenceof both PVD and UE. We accounted for herd, cow,and year as random effects in all 4 models. The overallprevalence of RTD in models 1, 2, 3, and 4 were 7.5,6.7, 11.6, and 2.6%, respectively. Days in milk at PBE,the interaction between days in milk and retained fetalmembranes, twinning, and the predicted transmittingability for calving interval were consistently significantrisk factors for positive scores in all 4 models. Considerablecalving difficulty [adjusted odds ratio (AOR)= 13.64], Holstein Friesian dam breed (AOR = 2.58),first lactation (AOR = 2.39), and body condition scoreat PBE (AOR = 1.64) were risk factors for a positivePVD score but not for a positive UE score. Fifth lactation(AOR = 1.69), a beef-sired calf (AOR = 1.46), andthe absence of a corpus luteum at PBE (AOR = 1.57)were risk factors for a positive UE score but not for apositive PVD score. These results support the hypothesisthat most of the risk factors for PVD and UE arethe same but some are distinctly different, implyingthat in some instances the 2 methods diagnose separatecomponents of the RTD complex.