The development of adverse behaviour in group–housed growing/ finishing pigs with intact tails was studied in a straw–flow housing system and in a part–slatted system with a commercial enrichment object. Food intake, body weight and behaviour were monitored over the finishing period, with tail biting outbreaks defined as an occasion where three or more pigs within a group had freshly damaged tails and tail biting behaviour was ongoing. Data from the two systems were analysed to identify tail–biting outbreaks and behavioural changes over time. Levels of pig manipulation were higher in the part–slatted system. Over time, pigs in both systems showed reduced interest in the enrichment provided, but not in each other. Despite the presence of the enrichment device, tail biting occurred in all groups in the part–slatted system, but only 1/12 groups in the straw–flow system. The amount of time occupied by manipulation of the enrichment provided was very significantly higher for straw than for the commercial object. Better design of enrichment strategies is therefore needed and should be based on species–relevant requirements.