Environmental enrichment can significantly improve poultry welfare, productivity and profitability by reducing the expression of harmful behaviours, like fear or feather pecking. However, some studies have yielded inconsistent results and many so-called enrichment stimuli elicited little or no interest. This probably reflected the wide array of stimuli used and the paucity of thought given to what a chicken (Gallus gallus domesticus) might find enriching. Clearly, the design of enrichment devices required more critical thought. Our immediate objectives were to establish chickens' specific preferences and thereby guide the development of practical enrichment strategies. First, we established that chicks showed increased use of an environment when it was enriched with simple, manipulable objects. Our use of video playback to assess chickens' responses to specific attributes of selected images then revealed that visual enrichment stimuli should incorporate movement, brightness, colour, and moderate complexity. Next, a survey revealed that almost 50% of the farmers who replied routinely played the radio to their flocks and that the perceived benefits included reduced aggression, improved health and increased productivity. Finally, we showed that a simple device consisting of a bunch of white strings is an extremely attractive pecking stimulus for chicks and adults of various strains of laying hens. Rather than rapidly losing interest in the devices the birds pecked progressively more at them with repeated exposure in short-term experiments. Furthermore, they were still being pecked at 17 and 2 weeks after their incorporation in the home pens of groups of 1-day-old chicks and adult hens, respectively. Even more encouragingly, the provision of string reduced feather pecking in birds of an experimental line showing high levels of this behavioural vice. It also reduced feather damage in caged layers at a commercial farm. The provision of string devices increases the opportunity for the birds to engage in behaviours that are fundamental to their nature, such as exploration and foraging. By maintaining lengthy interest and apparently reducing the expression of damaging feather pecking, string devices also satisfy other critical requirements of effective environmental enrichment. They have the added advantages of low cost, ready availability, ease of installation, and durability.
Collectively, these findings strongly support the hypotheses that extraneous stimulation is important to chickens and that the provision of appropriate visual, auditory and tactile enrichment stimuli can improve their welfare. Projecting images onto the walls of a poultry house could perhaps provide an additional source of visual stimulation, but this requires further investigation. Playing the radio was not only beneficial in terms of welfare and performance but it is probably one of the easiest and most practicable ways of enriching the environment for the birds and the stockpersons. The routine incorporation of string devices in rearing and laying cages is also considered likely to reduce boredom and feather pecking and thereby improve the birds' welfare and productivity. In conclusion, I wholeheartedly recommend the integrated application of string pecking devices and auditory enrichment.