Incubation temperature affects the expression of young precocial birds’ fear-related behaviours and neuroendocrine correlates

Abstract

The influence of embryonic microclimate on the behavioural development of birds remains unexplored. In this study, we experimentally tested whether chronic exposure to suboptimal temperatures engendered plasticity in the expression of fear-related behaviours and in the expression of the corticotropin-releasing factor in the brains of domestic chicks (Gallus g. domesticus). We compared the neurobehavioural phenotypes of a control group of chicks incubated in an optimal thermal environment (37.8 °C) with those of a group of experimental chicks exposed chronically in ovo to suboptimal temperatures (27.2 °C for 1 hour twice a day). Chronic exposure to a suboptimal temperature delayed hatching and decreased growth rate and experimental chicks had higher neophobic responses than controls in novel food and novel environment tests. In addition, experimental chicks showed higher expression of corticotropin-releasing factor than did controls in nuclei of the amygdala, a structure involved in the regulation of fear-related behaviours. In this study, we report the first evidence of the strong but underappreciated role of incubation microclimate on the development of birds’ behaviour and its neurobiological correlates.

Human behaviour at the origin of maternal effects on offspring behaviour in laying hens (Gallus gallus domesticus)

“…the discrimination test, H+ chicks clearly preferred their familiar cage mate to the stranger whereas H-chicks showed no preference. The preference showed by H+ chicks corresponds to a pattern previously observed in young Leghorn chicks [36]. In addition, the capacity of domestic chicks to discriminate between strangers and familiar conspecifics and their preference for familiar companions is well documented, even in day-old chicks [54].…”

“…Indeed, wild birds' neophobia appears to be plastic and more frequent in individuals experiencing high-risk environments [65]. Domestic chickens' neophobia (of food, objects, environment) and their capacity to perform a detour task were found to be plastic and influenced by their prehatch environment [35,36]. More generally, Galliforms' fearfulness is commonly known to be regulated by maternal effects [31,53,66,67].…”

“…[36]. This test was performed in a rectangular arena measuring (80 cm x 60 cm x 31 cm : length x width x height).…”

Behaviour, physiology and body mass of Nigerian indigenous hens during brooding

“…The results of the current study, however, showed no difference in the time spent by the hen sitting on the eggs as brooding progressed from the 1 st to the 3 rd week (88-92%), probably because of the need to provide adequate temperature and relative humidity (RH) needed for the embryonic development of the eggs (Reid et al, 2002). Sitting on the eggs is necessary for the transfer of heat from their body to the developing embryos (Bertin et al, 2018). The longer the bird spends off the nest the cooler the eggs become (Calder III, 2002) which is detrimental to the development of the embryo.…”

“…The longer the bird spends off the nest the cooler the eggs become (Calder III, 2002) which is detrimental to the development of the embryo. Eggs subjected to suboptimal incubation temperature of 27.2 °C for 1 h twice a day delayed hatching and decreased growth rate and showed greater neophobic responses in hatchlings (Bertin et al, 2018) Before the commencement of brooding, the hens pluck feathers from their breast and abdomen (brood patches) on the ventral surface, these reddish well-vascularized areas of skin to facilitate heat transfer to the eggs. Interestingly, this study observed that the BT (region of the body that comes in contact with the eggs) of the hens ranged from 37.8 °C to 39.5 °C which is just appropriate for the embryonic development.According to Lourens (2001) and Lourens et al (2007), incubation temperature of 37.8 °C is the thermal homeostasis in the chick embryo and ensures the best embryonic development and hatchability.…”