Keywords: Adaptation of the environment to the animal

This Opinion focuses on the value of manipulable materials, whose presence offers an effective means of enriching the living environment of pigs reared on slatted floors. They encourage the expression of investigative and manipulating behaviours but also, depending on the nature of the added materials, of maternal and foraging behaviours. They preclude behavioural frustration and induce positive emotions that can reduce deviant behaviours such as cannibalism and stereotyping and can limit negative emotions. Used properly, manipulable materials can have a positive impact on animal welfare. However, this impact is variable and can be negative, depending on the physical characteristics and distribution patterns of the manipulable materials. The impact is also negative when the manipulable materials introduce health risks. Before any routine use, the effect of the materials on welfare should be tested on the animal. In light of the prevalence of slatted floors on French livestock farms, it is desirable to make best use of such materials in ways that are worth developing further, under conditions that are adapted to the animal's welfare. Work on manipulable materials has been carried out very widely and has made it possible to identify the intrinsic qualities that retain the animals' interest and encourage investigation and manipulation. However, further work is still needed on animals' motives in using manipulable materials, on the latters' effectiveness, on methods of introduction and presentation,  on an economic evaluation of their distribution, on the development of new materials, on the health risks associated with their characteristics, on their effects on brain function, on the acceptability of their use by breeders and on the contribution of their use to the public's perception of livestock farming.