Investigating the importance of vision in poultry: comparing the behaviour of blind and sighted chickens

By S. Collins, B. Forkman, H. H. Kristensen, P. Sandøe & P. M. Hocking
Applied Animal Behaviour Science. Elsevier. 2011 

Abstract

Behaviour in poultry is predominately visually mediated and vision is important to the welfare of poultry. The relationship between vision, behaviour and welfare has primarily been investigated in relation to artificial lighting. Genetically blind chickens provide an alternative experimental paradigm for further investigating the importance of sight. The primary aim of the study was to investigate the importance of vision in the development and maintenance of behaviour in poultry by comparing the behaviour of 20 genetically blind chicks with that of 20 normally sighted chicks.

Behaviour was assessed in a social isolation test post hatch and at 28-30 days old, and in the chicks 8 home pens (4 blind; 4 sighted) at 42 days old. All birds were weighed at 0, 14, 28 and 42 days old. Analysis of home pen behaviour indicated that, compared to normally sighted chicks, blind chicks displayed increased preening and sitting behaviour, but reduced environmental pecking, behavioural synchrony and group aggregation. Blind chicks also exhibited abnormal behaviours - namely air pecking, star gazing, circle walking. Blind chicks weighed less than sighted chicks at 14, 28 and 42 days of age and appeared to be less stressed by social isolation compared to sighted chicks. It was concluded that blind chicks, as expected, have difficulty expressing behaviours that are normally visually mediated, and that their welfare is likely to be compromised as a result. 

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