|Cheng, Heng wei|
Submitted to: International Society of Applied Ethology
Publication Type: Abstract only
Publication Acceptance Date: 5/6/2002
Publication Date: 8/1/2002
Citation: FREIRE, R., CHENG, H. DEVELOPMENT OF SPATIAL COGNITION AND HIPPOCAMPUS STRUCTURE IN DOMESTIC CHICKS. INTERNATIONAL SOCIETY OF APPLIED ETHOLOGY. 2002. ABSTRACT P. 49. Interpretive Summary:
Technical Abstract: Broiler chickens in large groups do not space themselves evenly but instead crowd in particular areas, which may increase mortality and exacerbate welfare problems arising from social stress. One contributing factor may be a deficit in spatial skills arising from the absence of essential environmental factors during routine rearing. Experiments were conducted to examine the development of spatial skills, as part of a broader interest in the use of developmental plasticity to improve the match between animals and their captive environments. The rearing method involved imprinting chicks on an object and rearing them from 8-12 days of age in pairs in pens delineated with two wooden screens (occlusion-experienced treatment) or no wooden screens (occlusion-naive treatment). Neurological and behavioural evidence suggests that this period is crucial for the development of spatial skills. Occlusion-experienced chicks correctly reached a visually displaced imprinting stimulus (Binomial test, P<0.05) whereas occlusion-naive chicks performed at chance levels. In five detour test trials, occlusion-experienced chicks made fewer orientation errors both in the first trial (Kruskal-Wallis, P=0.07) and subsequent trials (Kruskal-Wallis, P=0.05). Orientation errors were negatively correlated with the amount of time spent out-of-view of the imprinting stimulus in the rearing pens (Spearman correlation coefficient, r=-0.58, P<0.05). Occlusion-experienced chicks had longer hippocampus dendrites (ANOVA, F1,14= 7.4, P<0.05) with more spines (ANOVA, F1,14= 10.6, P<0.01) than occlusion-naive chicks. Lastly, occlusion-experienced chicks moved more than occlusion-naive chicks when released into a large novel pen (ANOVA, F1,14= 11.9, P<0.01), though no difference in dispersal or use of the centre of the pen was found between the two treatments. Results presented here suggest that active experience of occlusion around 11 days of age shapes the domestic chick's spatial skills and hippocampus structure, supporting the hypothesis that enrichment-induced behavioural and neurological changes are dependent on the interaction with objects.