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Day-old chicks categorised on latency to peck, exhibit a stable fear pattern until 15 days of age
1Cátedra de Química Biológica, Departamento de Fisiología, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba. Av. Vélez Sarsfield 299, 5000, Córdoba, Argentina
Insights
Chicks categorized by pebble-pecking latency show distinct anxiety levels. High-latency chicks are more anxious, while low-latency chicks exhibit less fear, with sex influencing these fear patterns.
Area of Science:
- Animal Behavior
- Neuroscience
- Ethology
Background:
- Individual differences in behavior, such as fear and anxiety, are observable from a young age in various species.
- The latency to peck pebbles in day-old chicks can serve as an initial indicator of their behavioral disposition.
- Understanding these early indicators can provide insights into lifelong fear and anxiety patterns.
Purpose of the Study:
- To categorize day-old chicks based on latency to peck pebbles and assess their anxiety levels.
- To investigate the relationship between early behavioral categorization and later anxiety-related behaviors.
- To explore the influence of sex on fear and anxiety patterns in chicks.
Main Methods:
- Chicks were categorized into high (HL), moderate (ML), and low (LL) latency groups based on pebble-pecking.
- Anxiolytic effects of diazepam were tested on different latency groups.
- Behavioral tests at 15 days included open-field and tonic immobility tests.
- Central benzodiazepine receptor density was measured after acute stress.
Main Results:
- Diazepam reduced latency only in the HL group, indicating higher anxiety.
- The LL group showed lower locomotion latency and immobility, and diazepam insensitivity.
- The HL group exhibited the greatest increase in benzodiazepine receptor density post-stress.
- Sex influenced categorization, with more females in LL and more males in HL.
Conclusions:
- Early pebble-pecking latency is a valid predictor of anxiety and fear states in chicks.
- Fear patterns are influenced by sex and stable individual differences.
- This categorization method could serve as a test for fear/anxiety and aid in selecting high-performing fowls.
Abstract:
Day-old chicks of both sexes were individually categorised on the latency to peck pebbles and termed as high latency (HL), moderate latency (ML) or low latency (LL). Anxiolytic doses of diazepam diminished the latency only in the HL category, suggesting that it is the most anxious category. At 15 days of age, the LL category showed the lowest latency to ambulate in the open-field test, the lowest immobility duration in the tonic immobility test and insensitivity to anxiolytic doses of diazepam in both behavioural tests suggesting that it is the less anxious category. The increase of the central benzodiazepine receptor density induced by acute stressors was the highest in the most anxious and/or fearful HL category. There were more females than males in the LL category and inversely in the HL category there were more males. The results suggest that the fear pattern depends on the sex and inter-individual differences within a same sex which are stable across life. This could be used as a test for fear and/or anxiety state, and useful to choose fowls with the best performance later in life.