Can a facial action coding system (CatFACS) be used to determine the welfare state of cats with cerebellar hypoplasia?

Background- The impaired motor skills of cats living with cerebellar hypoplasia (CH) suggests they would be unable to practice normal behaviour, one of the five welfare needs. This study aimed to explore the use of facial action coding system (CatFACS) as a welfare assessment tool for cats with CH. Methods- Facial expressions (action units [AUs]) were defined as neutral/positive or negative by recording healthy cats (n = 89) during presumed aversive or relaxed scenarios. CH cats (n = 33) were then filmed and their facial expressions compared to those of the presumed positively- and negatively-valenced healthy cats. Results- Sixteen negative AUs were defined. CH cats performed more of these than healthy cats (p = 0.023) in the relaxed scenario. There was no difference in AU expression between three levels of CH severity (mild, moderate or severe) (p = 0.461). Conclusion- Cats perform distinct AUs when experiencing negatively-valenced arousal, the presence or absence of these AUs could be used to infer the welfare of healthy and CH cats. As there was no difference in AU expression between the three levels of CH severity, the behavioural restrictions CH imposes on cats does not necessarily indicate lower welfare and the reasons why CH cats perform more negatively associated AUs warrant further research.