The Effect of Blindness on the Development of Fear Response in Chickens of Different Ages

Abstract

The objective of this study was to examine the effect of blindness on the ontogeny of fear response. We used a genetically blind chicken model (rc chickens) and tested fear response based on tonic immobility (TI). There were four blind groups and four sighted groups of rc chickens in this study, and each group consisted of 45 chickens. We performed the TI test on days 2, 14, 28, and 70 to study the ontogeny of fear response. Blind chickens were more difficult to induce into a TI response and stayed in TI for a significantly shorter time compared to sighted controls. The results from the TI tests indicated that the blind males had a slower rate of developing a TI response (from Day 2 to Day 70) than blind females. Blindness in rc chickens is caused by a deletion in the GC1 locus, resulting in the disruption of cGMP metabolism. Besides causing the degeneration of rods and cones in the retina, cGMP deficiency may have a direct effect on brain cells, thereby suppressing tonic immobility. cGMP also seems to affect male sexual maturity differently than female sexual maturity. Our results indicated that the ontogeny of fear response was dependent on the interaction of age, sex, prior experience and visual input, and the ontogeny of TI response in rc chickens may not solely reflect the ontogeny of the fear response but also the physiological processes affected by the gene mutation.

The authors' abstract, as published at the source. Animals, 2026 · DOI ↗