A database systematically indexes articles from a given list of journals and other professional publications, and each database may search a different set of journals – a list of which should be clearly defined by that database.
Databases are more reliable than Internet search engines as they focus on scientific literature and list the sources they search. Although Internet search engines are free, they are often less reliable. Some bibliographic databases are freely available, and may be a better option than relying on Internet search engines. Other databases, however, require a subscription, and it will be up to veterinary practices and practitioners to decide on the most affordable options available to them.
It should be remembered that databases are tools to identify relevant papers. Whilst some databases contain full text articles, many do not, and so you will also need to find ways to access the papers you wish to read; how to do so is covered later in this chapter.
Why would a busy vet in practice want to spend the time, effort and resource searching the primary literature?
Searching the primary literature effectively can be time-consuming, but it can prove worthwhile, particularly when a search of the secondary sources has resulted in too few results, or when practitioners are writing an evidence summary, practice protocol or guideline.
Can’t I just rely on Internet search engines like Google for finding evidence?
To some extent this depends on you and how much time you have to browse the Web for information and analyse what you find to decide whether or not you can trust it. If that is all you can do, it is miles better than nothing! Three of the key issues are:
A lack of peer-review on the WebGeneric Internet search tools do not confine themselves to peer-reviewed information from the academic and scientific communities, and so, while they will include links to some high quality evidence, the amount of time it will take to locate this amid everything else that is listed can make them inefficient. The onus will be on you to spend time sifting through results and doing the analysis to discern the validity and currency of the evidence.
Search engines don’t always tell you what they are giving you in a systematic fashionUsing search engines, you also run a risk of missing some key evidence, as these tools do not take a systematic approach to indexing all the relevant veterinary science journals. Even when you do find promising results on Google, you may find that they cannot be accessed, either because they are hidden behind institutional subscriptions and so would require a membership or payment, or because they come lower down the results list (Google does not actually link to every result it lists).
The inability to publish a reproducible search strategyIn evidence-based medicine it is important to publish your search strategy so that it can be reproduced to update the search and so that others may evaluate it. This is not possible with a Google search, for reasons described later in this section.
We have provided some examples of the limitations of Internet search engines.
Google is a search engine that crawls the Web and retrieves results using an algorithm which, for commercial reasons, is a closely guarded secret. What we do know is that Google is not concerned with who published the information or the quality of the information. The ranking of search results on Google are subjective as they vary according to IP address, location and previous search history (i.e. which computer is being used, where it is located geographically and the previous searches conducted on it). The frequency and location of keywords and the number of other pages that link back to the page are also taken into account. So while great for browsing the Web, Google generates a search that is not reproducible by others.
Google ScholarGoogle Scholar is also a search engine, but it restricts the parts of the Web that it crawls to scholarly sources such as academic publishers, scholarly societies and university web sites. This means it can reveal useful results, but unlike bibliographic databases, it does not publish a list of the sources it is searching (in fact it keeps these a trade secret), and so we cannot say with confidence that we have performed a systematic search of all the relevant veterinary journals. However, Google Scholar does have the advantage that it searches the full-text of web resources, and so it may retrieve results that would not be found via bibliographic databases (which search the bibliographic data only, e.g. author, title, abstract, keywords).
WikipediaGoogle will often give you results from Wikipedia, the online encyclopaedia written collaboratively by Internet volunteers. Anyone with Internet access can make changes to Wikipedia articles, and people often contribute anonymously using a pseudonym. This has pros and cons: it can be updated very quickly, and articles are dynamic and so can be updated to reflect new evidence. However, the quality of articles depends on the skill and knowledge of individual authors, which can be hard to ascertain from anonymous contributions.
Free databases for veterinary sciences
There are freely available databases are on the Web, some examples of which are:
- PubMed covers the life sciences, including veterinary medicine, and has a focus on biomedicine.
- PubAg focuses on articles pertaining to production animals and animal welfare. Both of these are good places to start if you have limited access to veterinary databases.
Which databases have the best veterinary coverage?
- CAB Abstracts has been shown to give the greatest percentage coverage of journals with veterinary content (Grindlay et al., 2012), and so would be seen by many as the key database for EBVM.
However, CAB Abstracts is costly, and this can be prohibitive. For this reason the publishers, CABI, have created a child-product:
- VetMed Resource which contains a sub-set of the records in CAB Abstracts selected for their relevance to vets. It is said to have a similar percentage coverage of the veterinary journals to CAB Abstracts, and so may be a more affordable option. The only loss might be that it does not index some interdisciplinary journals that may be relevant to some areas of EBVM.
Some veterinary journals that may contain useful evidence are not indexed in PubMed/MEDLINE, but are likely to be included in CAB Abstracts. For example, PubMed/MEDLINE and some other databases do not index all the equine and exotics journals found in CAB Abstracts. Some additional journals found in CAB Abstracts compared to other databases may not contain the highest quality research. However, if you wish to conduct a systematic review of the veterinary literature you would want to use CAB Abstracts.
Key databases for veterinary sciences
The key databases that index veterinary journals are listed here, with an indication of subject coverage and access. Links to the publisher’s websites are also given, where further information about each database can be found.
|Database / Access information||Access||Subject coverage|
|CAB Abstracts||Subscription required||Applied life sciences, including agriculture, and veterinary and food sciences.|
|VetMed Resource||Subscription required||A sub-set of CAB Abstracts – articles tagged to the Veterinary Science subset of CAB Abstracts are also available via VetMed Resource.|
|PubMed||Free version of Medline||Life sciences, with focus on biomedicine but includes veterinary medicine|
|Medline||Subscription required||Life sciences, with focus on biomedicine (same data as PubMed but available via different delivery platforms, which offer some enhanced search functionality)|
|Web of Science Core Collection||Subscription required||Interdisciplinary citation database|
|Scopus||Subscription required||Interdisciplinary citation database|
|BIOSIS Citation Index||Subscription required||Biological sciences|
|Embase||Subscription required||Biomedical and pharmaceutical subjects|
|Zoological Record||Subscription required||Zoology and animal science|
|PubAg||Free||Production animals and animal welfare|
Finding creative ways to access more databases is a great idea, as relying on just one database, or just the free ones, is likely to compromise the level of recall of relevant evidence. Each database publishes a ‘Journals List’ which indicates the scope and subject coverage of the database, for example see the List of Journals Indexed for MEDLINE or the Veterinary Journals Indexed in PubMed. The coverage of information will overlap to some extent between different search tools, and given the inter-disciplinary nature of the veterinary sciences, searching across more than one database will increase the chances of locating relevant research.
Database delivery platforms and interfaces
Some of the databases listed above are available to purchase from different database providers and via different platforms. The different delivery platforms can offer different search interfaces, which may offer enhanced functionality (e.g. clearer presentation of Subject Headings). When reporting a database search, it is important to mention the platform you accessed it on to enable the search to be peer-reviewed and replicated (as different platforms can require different search strategies for optimum searching). Some of the main platforms, with links to the suppliers, are given below: