|Cheng, Heng Wei|
Submitted to: International Society of Applied Ethology
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2004
Publication Date: 6/18/2004
Citation: Dennis, R., Estevez, I., Cheng, H. 2004. Marked for stress. International Society of Applied Ethology. p. 18. Interpretive Summary:
Technical Abstract: We have shown that domestic fowl (Gallus gallus domesticus) marked for identification purposes receive higher levels of aggression from their unmarked counterparts. Differential aggressiveness due to manipulation of physical appearance suggests that birds may also be subject to differential levels of stress and exhibit differential catecholamine responses. One-day-old male broilers were housed from 1 to 10 wk of age in groups of 10 and 50 and containing 20%, 50%, or 100% of birds marked with black marker. Each group size by percent mark treatment combination was replicated seven times, although blood samples were collected from only six of the replicates. Body mass (BM), tonic immobility (TI), and fluctuating asymmetry (FA) were assessed and blood samples were collected for hormonal analysis from three marked and three unmarked birds per group. Body weight from 2 to 5 wk of age was lower in marked birds than unmarked birds in 20% and 50% pens (P<.05), which suggest that marked birds may be more stressed. Plasma catecholamine concentrations following manual restraint, revealed a suppressed epinephrine (EP) response and an increase in (DA) in marked birds of 20% pens (P<.05). Interestingly, EP response did not differ between the 20% unmarked and the 100% marked groups (P>.05). No significant differences were found in norepinephrine (NE) response (P>.05). These results suggest that marking may affect the performance of the birds as well as their stress levels, particularly when only a small proportion of group members are marked.