The physical environment of an animal is sometimes altered if it is found to cause problems for animal welfare. These changes are commonly quite specific (making changes to space, food, water, aspects of housing design such as flooring, or to other environmental factors such as air quality) and may be effective in preventing injuries or disease. However, such measures may not be implemented in practice (usually for economic reasons), and where implemented may cause other problems, as when concern for hygiene leads to animals being kept in barren conditions. Numerous ways have also been tried to diversify feeding methods in order to improve animal welfare, but specific changes to the environment such as these often have widespread effects, some of which may be detrimental. For example, inclusion of novel pen structures meant to enrich the environment may lead to increased aggression. A more general approach is therefore appropriate. One area where this is particularly relevant is handling and transport, when animals encounter environments that are wholly new to them. For environments where animals spend more time, several studies have attempted a 'biological approach' in which a biological functioning is considered while avoiding simplistic assumptions of 'natural is best'. We consider as examples systematic tests of environmental enrichment for pigs, novel designs for loose housing of lactating sows and their litters, and furnished cages for laying hens. Stringent tests of every design feature and their interactions are necessary to produce commercial designs from such studies.