R.B. Jones

Behavioural 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 chickens to approach and restraint by an experimenter were measured in Experiment 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<0.05). Furthermore, these birds that had received minimal human contact had higher plasma corticosterone concentrations after 12 min of handling 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 birds fear of humans is demonstrated by these results in which handling treatments, designed to affect differentially fear of humans, caused divergence in the behavioural and adrenocortical responses of birds to humans. The major objective of the present study was addressed in Experiment 2, in which the between-farm relationships between the behavioural responses to humans and the productivity of broiler chickens were examined at 22 commercial farms. Some of the behavioural variables were significantly correlated with feed conversion (feed to gain ratio). For example, the average number of birds that approached or remained within 750 mm of an experimenter in a standard test (variable BIRDSs) and the number of birds that remained forward and oriented forward or to the side when an experimenter closely approached in another standard test (REMAINFS) were significantly (P<0.01 and P<0.05, respectively) and negatively correlated with feed to gain ratio (FC) at the farm. The direction of these significant correlations indicate that feed conversion was poor at farms in which birds avoided the experimenter in the two standard tests. The variable BIRDSs was found to predict FC significantly (P<0.02), and this variable accounted for 28% of the variance in feed conversion at the farms. These significant relationships between the behavioural responses of birds to an experimenter and feed conversion suggest that fear of humans may be an important factor limiting the productivity of commercial broiler chickens. The precise mechanism(s) responsible for this inverse fear-productivity relationship 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.

Effects of regular handling on growth in male and female chicks of broiler and layer strains

1. The effects of regular handling on growth and gain: food ratios in male and female chicks of layer (two strains) and broiler strains were examined from hatching to 3 weeks of age. 2. Growth was significantly enhanced by regular handling in broilers and the females of the layer strains and gain : food ratios were generally greater in the handled birds. 3. There were no significant treatment effects on growth or gain : food ratios in males of the layer strains. 4. Males had higher relative weight gains and gain : food ratios than females.

Sociality in Japanese quail ( Coturnix japonica ) genetically selected for contrasting adrenocortical responsiveness

Abstract The growing realisation that selective breeding may offer rapid solutions to certain animal welfare problems and the associated production losses lends urgency to the search for suitable selection criteria. We have already shown that genetic selection of Japanese quail for a reduced (low stress, LS) rather than an exaggerated (high stress, HS) adrenocortical response to brief mechanical restraint was associated with marked reductions in underlying fearfulness, non-specific stress responsiveness and developmental instability. However, since genetic selection for one trait can also modify others, monitoring of other important characteristics is imperative before we can make any recommendations. Inappropriate levels of sociality (motivation to be near conspecifics) could cause pronounced social stress. The present study compared underlying sociality in LS and HS quail in two ways. In experiment 1, when undisturbed, same-line groups of six chicks were observed at 4 days of age we found that LS quail stayed closer together than HS ones. When naive, individually tested chicks were tested in a runway at 11–12 days of age in experiment 2, LS quail spent longer near a goal box containing cagemates than did the HS birds. Social proximity in the home cage and reinstatement responses in runway tests of social affiliation are positively related to underlying sociality. Therefore, these findings strongly suggest that underlying sociality is greater in quail of the LS than the HS line. Enhanced sociality could be regarded as an additional advantage of this type of selection programme, particularly if the phenomenon generalised to include commercially important species that are often housed at high stocking densities, like chickens or turkeys.

Treating Japanese quail with vitamin C does not facilitate their capture by the experimenter.

1. Vitamin C supplementation reduces fear of novel situations and of people. The present study examined its effects on the ease of capture of male Japanese quail by the experimenter. 2. At 20 d of age, quail received either vitamin C (ascorbyl-2-polyphosphate, APP, 1 g L-ascorbic acid/l) solution or untreated drinking water (UDW) for 24 h before they were mixed in 2 groups of 40 (20 APP + 20 UDW. All the birds in 1 group were caught individually by an unsighted experimenter whereas a sighted catcher captured the others. The birds identity was noted each time. This capture/recapture procedure was repeated 6 times for each group (12 capture trials per bird) and an overall capture rank across all 12 trials was assigned to each bird. 3. Regardless of whether the catcher was sighted or unsighted, the mean ranks of neither APP nor UDW quail differed significantly from the value expected by chance. Neither were there any linear trends in the effects of repeated testing. Thus, prior treatment with vitamin C neither facilitated nor hindered capture. 4. Body weights were similar in both treatment groups and there were no significant intra-individual correlations between body weight and capture rank. 5. Highly significant tendencies were found for individual birds to be caught at similar stages of each capture trial regardless of treatment or test situation. This finding sounds a cautionary note for all studies involving putatively random sampling of a population.