Mycoplasma bovis can be a commensal bacterial inhabitant of the upper respiratory tract of healthy bovines. However, under certain circumstances and conditions that are incompletely understood, M. bovis can be associated with a number of clinical syndromes, one of which is bovine respiratory disease (BRD). In Australia, there is little information on the prevalence and epidemiology M. bovis in beef production systems. The overall aim of this thesis was to help close this knowledge gap.Commercially available serological diagnostic methods for the detection of M. bovis-specific antibody have not been validated in the Australian cattle population. Arguably, more importantly, however is the fact that diagnostic sensitivity (Se) and specificity (Sp) and / or analytical sensitivity (ASe) and specificity (ASp) estimates for commercially available M. bovis sero-diagnostic tests are not available.The diagnostic Se and Sp were estimated for two currently available commercial M. bovis enzyme-linked immunosorbent assays (ELISAs), the BioK302 and BioK260 (Bio-X Diagnostics®, 2013a) from Bio-X Diagnostics® (Belgium), in addition to western blot analyses using a novel recombinant M. bovis protein. This was performed using a panel of reference sera from animals of known M. bovis infection status. Western blotting was found to have improved Se at 74% (95% CI: 16 – 98%), compared to the commercial ELISAs; BioK302: 47% (95% CI: 10% – 89%) and BioK260: 28% (95% CI: 1% – 92%). However, in terms of Sp the commercial ELISAs out performed western blotting; BioK302: 96% (95% CI: 87% – 99%); BioK260:100% (95% CI: 93% – 100%) and western blotting: 88% (95% CI: 56% – 98%) respectively. In terms of both Se and Sp combined, none of the methods assessed here performed well. As such, when interpreting the results obtained from these ELISAs, the potential impact imperfect Se and / or Sp can have needs to be considered.Despite the poor performance of the BioK302 and BioK260 ELISAs particularly in terms of Se, these tests were used to determine the sero-prevalence of M. bovis antibody in Australian feeder cattle at feedlot induction and draft (approximately 42 days on feed). Paired bovine sera from 1,354 randomly selected animals were sourced from a bovine serum bank (n = 35,160) collected as part of another study, The National Bovine Respiratory Disease Initiative. As the classification of the result of a single serum sample could differ between the BioK302 and BioK260, sero-prevalence estimates were obtained using the individual ELISA results in addition to series and parallel interpretation of the two ELISA kit results. The apparent sero-prevalence of M. bovis-specific antibody at feedlot induction estimates ranged from 2.4% – 6.8% (95% CI: 1.3% – 8.6%) and the apparent sero-prevalence estimates at draft ranged from 22.4% – 44.2% (95% CI: 19.1% – 48.6%). The level of sero-conversion to M. bovis between induction and draft was also determined. Only animals that were classified as sero-negative at induction were included in sero-conversion analyses. In the current study, 24.3% (95% CI: 20.8% – 27.7%) and 19.5% (95% CI: 17.3% – 21.7%) of animals sero-converted to M. bovis between induction and draft based on the BioK302 and dichotomised BioK260 ELISA results respectively.Using these ELISA results, an assessment of putative risk factors associated with sero-positivity at feedlot induction or sero-conversion between induction and draft was performed. An increased risk of sero-positivity at feedlot induction was found to be associated with; (i) history of exposure to a saleyard at least 27 days prior to induction, (ii) mixing with animals from another property at least 27 days prior to induction and; (iii) the size of the group of animals an animal was with 13 days prior to induction. While the region from which animals were sourced 28 days prior to induction was associated with a reduced risk of sero-positivity at feedlot induction. Risk factors that were found to be associated with a decreased risk of sero-conversion between induction and draft included; (i) breed; (ii) source region; and (iii) group size, while access to water shared with another pen of animals was associated with increased risk. Sero-conversion to M. bovis between induction and draft was strongly associated with the development of BRD with an odds ratio of 2.1 – 3.1 (95% CI: 1.4 – 4.7) during the early feeding period.This is the first Australian study that has investigated M. bovis in the feeder cattle population. The findings reported herein have improved the understanding of the currently available sero-detection methods in addition to providing sero-prevalence information which is essential for future studies when trying to determine sample size estimate. In addition, the identification of potential risk factors associated with sero-positivity to M. bovis and those associated with sero-conversion between induction and draft will inform future M. bovis epidemiological investigations. Improving the overall knowledge of the epidemiology of M. bovis in Australia will in turn, assist the development of targeted control measures and help reduce the economic impact of M. bovis-associated disease including BRD