Optimising oral fluid collection from groups of pigs: effect of housing system and provision of ropes.

The effective use of pooled oral fluid (OF) in disease surveillance requires that samples are representative of the group. The aim of this study was to develop a 'rope presentation' protocol to maximise the number of different pigs sampled from a pen of animals. Eight pens of grower pigs in 'fully slatted' accommodation (FS) and 'straw-kennels' (SK) were presented with a balanced sequence of 1-4 ropes. Ropes were presented for 60 min, and the chewing time/pig recorded. Oral fluid was extracted from all of the ropes. Rope provided for 60 min generated chewing in >80% of the group. Pigs in SK exhibited longer latency to interact with the rope (P<0.001), reduced percentage of pigs chewing (P<0.001), and a reduced mean total time spent chewing (P<0.001). An interaction was found between 'system' and 'number of ropes provided' (P<0.05). Increasing the number of ropes increased the mean total chewing time/pig only in the FS. The quantity of OF obtained correlated with the percentage of pigs that chewed the rope (P<0.001) and the mean total time spent chewing/pig (P<0.001). Where the group size was ≤25, presenting one rope for 45 min was sufficient to optimise the number of pigs sampled.