This thesis introduces systematic reviews for interventions, why they are used, and how they can benefit veterinary scientific research. Two examples were presented. The first discusses using the tool GRADE for quality assessment of outcomes for systematic reviews and meta-analyses. A critical review and meta-analysis is presented on the topic of vaccine efficacy for the disease Tritrichomonas foetus in beef cattle. This review used GRADE to help determine the quality of the outcomes that were used for this review and meta-analysis. The findings were reported in summary tables. The overall conclusion of this review was that there is a lack of conclusive evidence to support the use of this vaccine in areas where good biosecurity practices are in place, but readers can use the GRADE evidence tables to make their own decision about the results depending on their unique situation. Additionally, this review helped to point out that there were relatively few studies in cows and bulls and therefore the efficacy of the vaccine in these groups of cattle could not be assessed, and may serve as an area of future clinical research.

The second example given in this thesis describes an approach in meta-analysis to compare different treatments for the same disease or problem, indirectly, called a MTC meta-analysis. Only a few MTC meta-analyses have been published in veterinary medicine. An MTC would have been performed for the critical review and meta-analysis that was presented, as there were several treatments utilized that were compared with control (no treatment). This unfortunately could not be done, due to missing information in most of the manuscripts. The overall conclusion of this review was that the results suggest that there is evidence that anthelmintic use has an effect on ADG in beef cattle production systems in a northern climate of the United States and that no conclusion could be made on weight gain as a meta-analysis could not be conducted due to poor reporting. This conclusion points out that better reporting throughout the current studies would have been needed to fully understand the magnitude of effect anthelmintic interventions for improved ADG and weight gains in beef cattle in northern climates of the United States. Furthermore, additional research would be necessary to draw conclusions regarding the timing anthelmintic interventions as well as a ranking of different anthelmintic products.

The two critical reviews and meta-analyses that are presented in this thesis illustrate the need for quality primary research and comprehensive reporting of primary research. There are key places where veterinary researchers can help to make literature more usable for systematic reviews. Properly reporting measures of precision such as standard errors or standard deviations, transparency in the materials and methods so that extraction of data such as treated and control populations, sex of animals used, or number lost to follow-up, etc. are easily done. Researchers should take these important parameters into consideration prior to starting their research in order to minimize biases and attempt to do so throughout the trial. High quality, and transparent studies are much easier to include in systematic reviews and meta-analyses as well as obtain much more useful information.

Finally, systematic reviews are an important part of medical literature. It seems important for the veterinary medical community to also see these benefits and begin to incorporate systematic reviews more often into veterinary research. There is a movement to ensure that medical treatments are based on the best data available. Therefore, systematic reviews should be used as part of the research process and should play a role in development and design of new research. Many human medical journals are urging or requiring researchers to perform or utilize an existing systematic review before starting a trial. Although this may seem like it might add significant time to the research process, this extra step can help to guide research in a more effective way and decrease repetition.