Studies on the Visual Acuity of Pigs Using Shape Discrimination Learning

Abstract

The objective of this study was to determine the visual acuity of pigs. Six pigs were trained to discriminate between a Landolt ring and an ordinary ring of equal size associated with feed. The left and right positions of the 2 targets were shifted according to the Gellermann series. After the pigs were fully trained, their visual acuity was determined by changing the size of the rings or the distance from the target. The pigs were subjected daily to 1 or 2 sessions which consisted of 30 trials each. The criterion of successful discrimination was 3 consecutive sessions with more than 21 correct choices (P<0.05, Chi-square test). Two castrated pigs were not able to learn the experimental procedure. The best scores of visual acuity in the 4 female pigs were 0.017, 0.034, 0.035 and 0.07.