INVESTIGADORES
MARIN Raul Hector
artículos
Título:
Effects of an acute stressor on fear and on the social reinstatement responses of domestic chiks to cagemates and strangers.
Autor/es:
MARIN R. H.; FREYTES P.; GUZMAN D. A.; JONES, R. B.
Revista:
APPLIED ANIMAL BEHAVIOUR SCIENCE
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Año: 2001 vol. 71 p. 57 - 66
ISSN:
0168-1591
Resumen:
Genetic selection for appropriate levels of sociality (motivation to be with conspeci®cs) could
bene®t poultry welfare and performance. Runway tests that require chicks to traverse a corridor in
order to reach other chicks in a goal box are commonly used to measure this behavioural trait.
However, we need to determine if the chicks´ responses in such tests are sensitive to certain
experiential variables before we can recommend possible selection criteria for future breeding
programmes. The present study focused on fear and on the identity of the stimulus birds. Broiler
chicks either remained undisturbed or were exposed to an acute stressor (mechanical restraint)
before their tonic immobility fear responses were measured 1 h later in Experiment 1. Exposure to
the stressor significantly prolonged tonic immobility and, hence, presumably, underlying fear levels.
In Experiment 2, the responses of stressed chicks and undisturbed controls were assessed when they
were tested individually in a runway with a goal box containing either familiar or unfamiliar chicks
of the same age. Our finding that stressed chicks emerged from the start box sooner and spent longer
near the stimulus birds suggests that exposure to a frightening event increased social reinstatement
motivation. Furthermore, social affiliation was more pronounced when the goal box contained
familiar cagemates rather than strange chicks, regardless of prior treatment. This finding
demonstrates that broiler chicks that were housed in groups of twelve can discriminate between
familiar and unfamiliar conspecifics encountered in novel surroundings. Thus, sociality was
positively associated with fearfulness and broilers clearly showed social discrimination in runway
tests. These findings highlight the dangers of disregarding variables, such as fear and the capacity
for social recognition in tests of social motivation. We strongly recommend that exposure to
frightening events prior to test should be avoided and that the identity of the birds in the runway
goal box should be standardized, i.e. either familiar or unfamiliar, and noted.