Background: Use of oral fluid specimens in swine research and diagnostics has become commonplace. Objective of the present study was to evaluate the effect of the number of ropes provided and location in the pen on oral fluid sampling.

Sixty 5-week-old pigs were divided into two groups of 30 (15 gilts, 15 barrows) and housed in two pens identical in size and design. The effect of the number of ropes in the pen on pig oral fluid sampling behavior was evaluated by varying the number of ropes in the pen (1-4). Pig preference for rope location was assessed by observing pigs with 4 ropes in the pen (one at each corner). Four cameras synchronously took pictures at 2 second intervals throughout the sampling period to document pig interactions with the rope. "Pig interaction" was defined as a picture showing a pig's mouth closed around the rope. Oral fluid was collected at the end of each sampling period, aggregated, and volume recorded.

Results: Observations were analyzed at both group and individual level. Mean oral fluid volume and pig interaction increased when more ropes were provided, but 89% of pigs interacted with one rope in the pen. Given a choice of 4 ropes, pigs showed a significant bias toward location.

Conclusions: The data support the interpretation that one rope is sufficient to collect a sample representative of the group. Providing additional ropes increases volume, but this does not increase diagnostic utility. The data likewise suggest that pigs may have a preference for location; this observation will require additional exploration to achieve better understanding.