Background: Lameness in dairy cows has been an ongoing concern of great relevance to animal welfare and productivity in modern dairy production. Many studies have examined associations between various factors related to housing, management, and the individual animal and the occurrence of lameness. The objective of this systematic review was to answer the research question “what are risk factors associated with lameness in dairy cows that are housed in free stall barns or tie stall facilities”. Furthermore, we performed a synthesis of current evidence on certain risk factors by means of a meta-analysis to illustrate the strength of their association with bovine lameness. Results: Following pre-defined procedures and inclusion criteria in accordance with the PRISMA statement, two observers independently included 53 articles out of a pool of 1941 articles which had been retrieved by a broad literature research in a first step. 128 factors that have been associated with lameness were identified in those papers. Meta-analyses were conducted for five factors presented in six different studies: Body condition score, presence of claw overgrowth, days in milk, herd size, and parity. Results indicated that a body condition score of ≤2.5/5 is associated with increased odds of lameness. A higher risk of being lame was found for the presence of claw overgrowth, the first 120 days in milk, larger herd sizes, and increasing parity. Throughout the study, we encountered profound difficulties in retrieving data and information of sufficient quality from primary articles as well as in recovering comparable studies. Conclusions: We learned that an abundance of literature on bovine lameness exists. To adequately address a problem of this importance to both animal welfare and economic viability, solid evidence is required in the future to develop effective intervention strategies. Therefore, a consistent working definition of lameness and specific risk factors should be an option to consider.

Background: Parafilaria bovicola(Nematoda: Filariidae) causes cutaneous bleedings in bovine species. Flies serve as intermediate hosts. In recent years, reports on bovine parafilariosis have become more frequent, corroborating the necessity of reliable diagnostic interventions especially since no molecular or serological test has been available. We aimed to establish a polymerase chain reaction assay to detect DNA ofP. bovicolain flies, skin biopsies and serohemorraghic exudates of bleeding spots.Methods: PCRs targeting the cytochromecoxidase subunit 1 (cox1) gene and the internal transcribed spacer region (ITS) of the ribosomal RNA gene cluster were evaluated for their diagnostic sensitivity as well as performance and specificity on biopsy and serohemorrhagic exudate samples fromP. bovicola-infected cattle.Results: Using serohemorrhagic exudates (n = 6), biopsies (n = 2) and flies (n = 1), the PCR targeting thecox1 gene resulted in a gel band of almost 700 bp. Cloning, sequencing, and removal of primer sequences yielded a 649-bp fragment of theP. bovicola cox1 gene. The PCR targeting the ITS region showed a band of about 1100 bp. Cloning, sequencing, and removal of primer sequences resulted in a 1083 bp stretch of theP. bovicolaITS region. Testing samples from presumably affected animals, thecox1-PCR resulted in bands with the expected size and they were all confirmed asP. bovicolaby sequencing. In contrast, the ITS-PCR proved to be less sensitive and less specific and additionally amplified the ITS region ofMusca domesticaor buttercup DNA. When analysing for sensitivity, thecox1-PCR yielded visible bands up to 2 ng of genomic DNA, whereas the ITS-PCR produced bands up to 3 ng. In a plasmid dilution series, the minimum number of target DNA copies was 10²for thecox1-PCR and 10¹in the ITS-PCR.Conclusions: The evaluatedcox1-PCR enables reliable detection ofP. bovicolaDNA in skin biopsies and serohemorrhagic exudates. This PCR and, to a limited extent, the ITS-PCR, may help evaluate different therapeutic approaches. Furthermore, thecox1-PCR may be useful for epidemiological studies on the geographical distribution ofP. bovicola. Further understanding of the epidemiology of this parasite will help develop and implement effective control strategies.