Comparative study on stress-induced hyperthermia, level of fear and behaviour of two genetically selected strains of domestic chicks to playback calls

Abstract

Feed and alarm calls induce arousal in chicks, the former for feeding and the latter for danger. However, the response of birds genetically selected for meat or egg production to these calls have not been investigated. Thirty-six chicks each of the ISA Brown pullet and FUNAAB Alpha broiler (2 weeks old) were randomly allocated into three groups per strain and subjected to three playbacks: no call (NCP), feed call (FCP) and alarm call (ACP) continuously for 1 h. The test was carried out for 3 days/week for two weeks. The behaviours monitored were foraging, feeding, pecking (grouped as oral-related behaviour, ORB), freezing and clustering (grouped as fear-related behaviour, FRB). The eye (ET) and under wing (WT) temperatures were measured before and after each call and the change (ΔET and ΔWT) calculated. Tonic immobility (TI) test was performed after each call and the number of attempts to induce TI (NOATI) and the duration of TI (DTI) was recorded. Data on these two behavioural categories were subjected to General Linear Model analyses separately for each call having strain and day as fixed factors. The ΔET, ΔWT, NOATI and DTI were analyzed using Mann-Whitney U test. On both days, ΔET and ΔWT was similar after exposure to 1 h of FCP, ACP and NCP. FCP caused more (P < 0.001) ΔWT in pullet than broiler. Fear responses during FCP was not affected (P > 0.05) by day and strain. Strain × day interaction influenced (P < 0.05) only ORB, higher in the pullet on the 2nd day of FCP. Both strains showed similar ORB and FRB during FCP with ORB greater (P < 0.05) on the 2nd day. The ACP caused more (P < 0.05) ΔWT in broiler than pullet. Fear response to ACP was similar on both days. Although, DTI was similar for both strains, NOATI was greater (P < 0.001) in broiler than pullet. Interestingly, during NCP; ORB and FRB were similar on both days and for both strains. Although, fear response was similar on both days, DTI was greater (P < 0.05) in pullet than broiler. Finally, there was no significant (P > 0.05) strain × day or strain effects on ORB and FRB, with ORB greater (P < 0.05) on the 2nd day. In conclusion, pullet and broiler chicks showed greater arousal (higher ΔWT) to FCP and ACP, respectively. The pullets showed more fear responses during NCP and ACP than the broilers. The ORB and FRB were similar in both strains during each of the three calls.