Pen-mate directed behaviour in ad libitum fed pigs given different quantities and frequencies of straw

Abstract Straw stimulates explorative behaviour and is therefore attractive to pigs. Further, it can be effective in reducing negative pen-mate directed behaviours. Under most commercial conditions, straw can only be used in limited amounts as it can be difficult to handle in most vacuum slurry systems and is expensive. In addition, straw needs to remain fresh in order to have a degree of novelty. The aim of this study was to investigate pen-mate directed behaviour in pigs given different straw treatments. Pigs were assigned to one of five treatments testing either quantity or frequency of chopped straw provision with 20 replicates of each treatment (pen was regarded as the experimental unit). The treatments were as follows: T25: 25 g of straw/pig/d, T50: 50 g of straw/pig/d, T100: 100 g of straw/pig/d, T2×50: 50 g of straw/pig twice/d, T4×25: 25 g of straw/pig four times/d. Treatment T100 functioned as a control treatment, against which the other treatments (quantities T25 and T50) and frequencies of straw allocations (T2×50 and T4×25) were tested. Three focal pigs per pen were randomly chosen and observed for 15 min per hour where tail-in-mouth, ear-in-mouth, aggression and other pen-mate directed behaviour were recorded. In addition, residual straw in the pens was assessed using four categories ranging from straw in a thin layer; little straw; few straws; and soiled straw. Pigs were active for about 30% of the registered time, but overall no differences in total pen-mate directed behaviour (tail-in-mouth, ear-in-mouth, aggression and other pen-mate directed behaviour) were found in quantity or frequency of straw provision ( P >0.05). Activity levels and patterns were similar in all treatments with a morning peak of activity followed by an increasing activity level throughout the day. The pigs were active for about 30% of the day corresponding to less than 5 h per day. Of the active time, an average of 17 min was spent on pen-mate directed behaviour. Only minor differences were found in the residual straw assessment, T25 had a higher percentage of little straw left compared to T50 and T100 ( P P >0.05). Further, there was no difference in activity and pen-mate directed behaviour of pigs when the frequency of straw allocation was increased from one to two times (T2×50) or four times (T4×25) per day ( P >0.05).