Journal of Animal Science and Veterinary Medicine

The impact of breed on various behavioural traits has been documented across numerous avian species; however, there exists a scarcity of studies focusing on commonly raised broiler chickens. Fear, characterised as a detrimental affective state, serves as an indicator of distress and is correlated with adverse implications for the welfare and productivity of livestock. This investigation sought to evaluate fear-related behaviours in commonly raised broiler chickens of four distinct genotypes (Arbor Acres, Hubbard, Ross, and Cobb) at weeks 3, 5, 7, and 9 of age. A total of 140 birds (35 individuals per breed) were utilized, all derived from a common genetic lineage. Tonic immobility and emergence tests were conducted at weeks 3, 5, 7, and 9, respectively. Statistical analyses were performed employing Kruskal-Wallis tests and Mann-Whitney U tests. At the 3rd week of observation, the duration of tonic immobility exhibited a significant association with the breed (χ2=10.686, DF=3, p=0.014); however, this association was not significant by the 7th week (χ2=6.349, DF=3, p=0.096). Moreover, the latency to emerge from a dark enclosure was significantly influenced by plumage colour (χ2 =8.9229, DF=2, p = 0.01), with the shortest emergence latency recorded in black NIT. Breed significantly affected the latency to emerge from the box at both observation weeks (χ2=20.224, DF=3, p= 0.00 and χ2=19.419, DF=3, p=0.00). Conversely, no significant effects of sex were observed on the duration of tonic immobility at either observation week (Ų =2344.500, ž=-0.366, p=0.714 and Ų=2135.500, ž=-1.094, p=0.274). While the latency to emerge from the box was not significantly associated with sex at the 7th week of observation, a significant association was noted with the breed at the 9th week (Ų =2285.000, ž=-0.673, p=.501 and Ų=1883.500, ž=-2.230, p=.026). Remarkably, at the 9th week, females displayed a shorter latency to emerge from the box compared to males, indicating varying fear responses. In conclusion, breed exerted a discernible influence on fear levels in commonly raised broiler chickens, with Hubbard birds demonstrating the highest level of fear across two statistically significant fear indicators (prolonged emergence duration and tonic immobility).