Preference experiments were used to identify features of ramp design that influence the voluntary use of ramps by young pigs. In seven experiments, groups of pigs, aged 7-8 wk, were given free access to four different ramps simultaneously. The animals' behavior was monitored to identify the amount of time spent on the ramps and the number of pigs that failed to use specific designs. Slope, in the range of 20-32° from the horizontal, had a major influence on the pigs' behavior, with the shallower slopes attracting more use than steep ones. Pigs preferred ramps with angle-iron cleats (cross-laid on the ramps to provide foot-holds) spaced every 50 or 100 mm rather than 200 or 300 mm. Cleat height, in the range of 10-40 mm, had little effect. Pigs showed a slight preference for ramps with solid or open (wire mesh) side walls, compared to ramps partially enclosed by a railing. Reduced width (510 vs. 710 mm) was not a major impediment to ramp use, although the narrow ramps were used somewhat less, by a degree proportional to their smaller width. Level of illumination (up to 1200 lx) had no major effect. A staircase composed of 20 small steps was used at least as readily as a ramp of similar slope, but staircase designs with fewer, larger steps were not preferred. The results suggest that a ramp sloped at 20-24°, with cleats cross-laid every 50-100 mm, would provide a feasible design with good acceptance by young pigs, either for loading pigs or for two-level housing systems.
Phillips, P. A., Thompson, B. K., & Fraser, D. (1988). Preference tests of ramp designs for young pigs. Canadian Journal of Animal Science, 68(1), 41-48.