Early T-maze behaviour and subsequent growth in commercial broiler flocks

Abstract

Two batches of 2000 mixed-sex broiler chicks were obtained, one in summer and one in winter. Each flock was housed on the floor at a commercial farm. At 2 or 3 d of age, the latencies to escape from a T-maze were measured in 1044 and 1180 chicks in the summer and winter flocks, respectively. Chicks were assigned to high (HP), moderate (MP) or low (LP) performance categories if their escape latencies were below 40 s, between 40 to 90 s, or above 90 s, respectively. Ninety male and 90 female chicks from each of the 3 categories were weighed when they were 3 d old. The birds then remained undisturbed, apart from routine maintenance, until similar numbers were weighed at 49 d of age. Some birds may have been weighed at both ages. Body weights were higher in males than females and higher in the winter than summer flock at 3 d of age. Significant main effects of chick category as well as gender and season were found at 49 d of age. There were no significant interactions. As expected, 49-d body weights were higher in males than females and in the flock reared in winter than in summer. 5. HP chicks (those that showed rapid escape from the T-maze at 3 d) were also significantly heavier at 49 d than their LP counterparts, with MP chicks occupying an intermediate position. This suggests that early performance in a T-maze test is positively associated with subsequent growth. Furthermore, this relationship was apparent in each of the 2 flocks. Given this positive association, we suggest that this simple, rapid and non-invasive behavioural test could be a useful selection criterion for future breeding programmes.

Growth heterogeneity in broiler breeder pullets is settled before the onset of feed restriction but is not predicted by size at hatch

“…It is possible that the small effect (HP 2.3% heavier than LP at 8 wk; P < 0.02) of sociality on growth reported by Marin et al (2003) is masked in feed-restricted settings, where other factors become determining of individual growth rate differences, or that the cost of increased social interactions outweighs the stress-reducing effects in HP individuals. It is further possible that the difference between the results of Marin et al (1999Marin et al ( , 2003 and our findings is influenced by the main stressors experienced by the birds. Although the stress of living in a large-scale flock may be 1 of the major stressors in the life of an ad libitum-fed broiler, feed restriction can be expected to be the main cause of stress in broiler breeders, and although social support can successfully buffer social stress in the first case, it is probably much less effective at alleviating restriction-induced stress (Rault, 2012).…”

“…It was hypothesized previously that highly social and less fearful animals experience a better welfare situation in large-scale flocks, with improved growth as less energy is directed toward stress and fear responses (Kikusui et al, 2006;Siegel et al, 2008). Comparing the performance of individual chicks in a sociality T-maze at just 2 to 3 d, Marin et al (1999Marin et al ( , 2003 found a positive correlation between early social behavior and later slaughter weight that was reproduced over a range of environments. In our study, T-maze performance at 2 d showed no correlation with growth at any age or with performance in the same maze at 3 wk of age.…”

“…Although the overall growth rate is certainly affected by feed restriction, the differences in growth rate are retained for the full 4-wk period studied here. It has been proposed previously that appetite (or feed consumption), water consumption, and yolk use are the determining factors for growth potential in young chicks (Pinchasov, 1991;Marin et al, 1999), and only differences in feed and water intake are likely explanations for the higher weight gain (up to 40% in Exp. 4) already seen during the first day of feeding in animals later growing to be large at 4 wk.…”

“…3 was tested using a social reinstatement T-maze as previously described by Marin et al (1999). Chicks were first tested at 2 d of age and then retested at 3 wk of age.…”

“…First, highly social individuals may experience reduced stress when raised in large flocks. We have previously reported a possible correlation between sociality and growth performance in broiler breeders (Lindholm et al, 2015), and others have shown it in ad libitum-fed broilers (Marin et al, 1999(Marin et al, , 2003. Second, variations in the development of thermoregulatory capacity have previously been linked to early growth performance (Peebles et al, 2004) and may have long-term effects on metabolic rate and growth.…”