BEHAVIORAL-RESPONSES TO HUMANS AND THE PRODUCTIVITY OF COMMERCIAL BROILER-CHICKENS

The effects of differing degrees of previous exposure to humans on the subsequent behavioural and adrenocortical responses of broiler chicke ns to approach and restraint by an experimenter were measured in Exper iment 1. A higher proportion of birds that had received minimal human contact withdrew as an experimenter approached in a standard test than birds that had received regular human contact (0.77 vs. 0.46, P < 0.0 5). Furthermore, these birds that had received minimal human contact h ad higher plasma corticosterone concentrations after 12 min of handlin g than birds in the latter treatment (12.61 vs. 5.40 nmol l(-1), P < 0 .05). The usefulness of behavioural measures as indicators of the bird 's fear of humans is demonstrated by these results in which handling t reatments, designed to affect differentially fear of humans, caused di vergence in the behavioural and adrenocortical responses of birds to h umans. The major objective of the present study was addressed in Exper iment 2, in which the between-farm relationships between the behaviour al responses to humans and the productivity of broiler chickens were e xamined at 22 commercial farms. Some of the behavioural variables were significantly correlated with feed conversion (feed to gain ratio). F or example, the average number of birds that approached or remained wi thin 750 mm of an experimenter in a standard test (variable BIRDS(s)) and the number of birds that remained forward and oriented forward or to the side when an experimenter closely approached in another standar d test (REMAIN(FS)) were significantly (P < 0.01 and P < 0.05, respect ively) and negatively correlated with feed to gain ratio (FC) at the f arm. The direction of these significant correlations indicate that fee d conversion was poor at farms in which birds avoided the experimenter in the two standard tests. The variable BIRDS(s) was found to predict FC significantly (P < 0.02), and this variable accounted for 28% of t he variance in feed conversion at the farms. These significant relatio nships between the behavioural responses of birds to an experimenter a nd feed conversion suggest that fear of humans may be an important fac tor limiting the productivity of commercial broiler chickens. The prec ise mechanism(s) responsible for this inverse fear-productivity relati onship in broiler chickens is unclear. However, attention is drawn to the potential for improving the productivity and welfare of commercial broiler chickens by identifying and manipulating those human factors which are influential in commercial units.