Table 1.

Factors used to classify the papers, the different levels, and the explanation of how each paper was classified.

Factor	Levels	Explanation
Animal species	Cattle Equine Fur animals Goat Poultry Rabbit Sheep Swine Other General	Each paper was classified according to the main farm animal species it dealt with, and each animal species was further classified according to the animal category (e.g., cattle was further subdivided in dairy, beef, and calf; swine was further subdivided in fattening pig, sow, piglet/other). A paper was classified as other if it dealt with other minor animal species or as general if it was of a general wide approach and not involving given animal species. A paper dealing with more than one species was classified in more than one class
Type of study	Methodological Research Assessment Other	Each paper was classified as methodological if it described a method applied or the development of a methodology (e.g., validation), as a research if it was an original applicative study with data produced by the research, as an assessment if it described an animal welfare assessment or its application, and as other if it did not fall in any of these classifications. A single paper was classified in more than one class if it considered more than one of the aspects listed
Scenario	On farm At slaughter During transport Not reported	Each paper was classified according to its scenario of application or with the scenario it dealt with: on farm, at slaughter, and/or during transport. A single paper was classified in more than one class if it considered more than one scenario
Organic farming	Yes No Not reported	Each paper was classified as dealing with organic farming (yes) if it included the application in organic farms (according to organic principles) or of it dealt with comparisons of conventional (no) vs. organic production systems (yes) and as not organic (no) if the application was on conventional farms and as not reported if it was not specified in the full text