Introduction to systematic reviews in animal agriculture and veterinary medicine.

This article is the first in a series of six articles related to systematic reviews in animal agriculture and veterinary medicine. In this article, we overview the methodology of systematic reviews and provide a discussion of their use. Systematic reviews differ qualitatively from traditional reviews by explicitly defining a specific review question, employing methods to reduce bias in the selection and inclusion of studies that address the review question (including a systematic and specified search strategy, and selection of studies based on explicit eligibility criteria), an assessment of the risk of bias for included studies and objectively summarizing the results qualitatively or quantitatively (i.e. via meta-analysis). Systematic reviews have been widely used to address human healthcare questions and are increasingly being used in veterinary medicine. Systematic reviews can provide veterinarians and other decision-makers with a scientifically defensible summary of the current state of knowledge on a topic without the need for the end-user to read the vast amount of primary research related to that topic.