Behaviour of fattening pigs fed with liquid feed and dry feed

Facilities for fattening pigs offer limited possibilities for exploration and wet feeding systems, where the pigs drink the food instead of eating it, have expanded on behalf of dry feeding systems. As little has been made to evaluate liquid feeding from the point of view of the pigs, the aims of this study were to compare behaviour in general and behaviour at feeding in particular of fatteners offered dry or wet feed. The study was carried out in an integrated herd with age segregated rearing of pigs and access to both feeding systems in the fattening units. Apart from the feeding system, the pens were identical and they were managed by the same staff. Pigs were allocated to the fattening units at 20 kg body weight and their behaviour was studied through web cameras during day hours (07.00 to 19.00).

Pigs performed well in both systems, but differed in behaviour. Fattening pigs offered dry feed spent longer time (P < 0.001) eating at every feeding occasion. They also expressed fewer regroupings during the first week (P < 0.001) when the social rank not yet was established. Pigs fed liquid feed regrouped during the effective eating time, while pigs fed dry feed regrouped when the first pig already had left the through which rather reflected seeking for leftover feed. Restlessness was rarely recorded before feeding, but rather frequently afterwards. During week 5-9 restlessness was more frequently recorded among pigs offered wet feed. Pigs offered liquid feed expressed unwanted behaviour in terms of belly-nosing, and nibbling of ear or tail to a somewhat higher extent than pigs offered dry feed. In both systems the pigs were occupying themselves with straw when offered, but only as long as they regarded it as new, i.e., for around 45 min following each provision.

Pigs performed equivalent in both systems, but from an animal welfare view we recommend dry feed to growing pigs and suggest that liquid feed systems ought to be reserved for systems using alternative feed supplies like whey or other liquid leftovers from the food industry.