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

Abstract

Regular visual presence of humans is known to reduce chickens' human-generated stress responses. Here we questioned whether, more than mere visual presence, human behaviour affects laying hen behaviour and subsequently their offspring's behaviour. We hypothesized that human behaviour triggers maternal effects via variations in yolk hormone levels. For five consecutive weeks, two groups of hens were exposed to the same durations of human presence (30 min twice a day, five days a week) but the behaviour of the human differed between groups. The first group (H+) was exposed to predictable arrival of the experimenter, slow movements combined with static presence, stroking during handling and human voice. Whereas the second group of hens (H-) was exposed to unpredictable arrival of the experimenter which remained silent, in motion, and did not provide stroking during handling. At the end of the treatment, we evaluated egg quality and offspring behaviour. We found that avoidance of the experimenter by H+ hens but not by H-hens decreased significantly. Fertility rates and concentrations of yolk progesterone and estradiol in H+ hens' eggs were higher than in H-hens' eggs. Fear of humans, neophobia or the capacity to solve a detour task did not differ significantly between H+ and H-chicks. Social discrimination tests showed that H+ chicks but not H-chicks typically preferred a familiar conspecific to a stranger. These results show that, with the same duration in the presence of the birds, humans through their behaviour engender variations in fertility rates, yolk hormone levels and transgenerational effects on social skills. Rarely explored, our data suggest that maternal effects influence filial imprinting. These data have broad implications for laboratory, commercial systems and conservatory programs where the inevitable presence of humans could trigger maternal effects on offspring phenotype.

Maternal age and maternal environment affect stress reactivity and measures of social behaviour in laying hens

“…In their lifetimes, layer breeders in commercial production can produce approximately 115 female offspring 10 , meaning that their experiences c Previous research has shown that hens subjected to a moderate heat challenge for ve consecutive weeks laid eggs with higher concentrations of yolk steroid hormones (progesterone, testosterone and estradiol) and had lighter and calmer offspring than control 11 . In the Japanese quail, human behaviour during handling (predictable and gentle versus unpredictable and fast) also affected the concentration of progesterone and estradiol in yolk and on offspring social discrimination skills 12 . Likewise, Japanese quails subjected to stressful events, such as sudden movement or unpredictable noise, laid eggs with higher yolk testosterone and progesterone, and produced chicks more sensitive to social separation (i.e., vocalized more during emergence and open-eld tests) 13 .…”

Maternal Age and Maternal Environment Affect Egg Composition, Yolk Testosterone, Offspring Growth and Behaviour in Laying Hens

“…This discrepancy con rms the importance of time of stress exposure and suggests that maternal effects are caused by different mechanisms over time. While stressors experienced by the pullet during development might affect her offspring primarily through epigenetics 50 , stress exposure during adulthood seems to lead to changes in concentration of egg yolk hormones, as seen in lizards 51 , quails 52,53 and laying hens 17,54 . Traditionally, maternally transferred androgens such as testosterone have been suggested as the primary mediator of these effects 19 , but research has also focused on other hormones including glucocorticoids 20 and thyroid hormones 4 .…”

Effects of human-animal relationship on animal productivity and welfare

“…Similarly, Edwards et al (2010) showed for laying hens that 12 min/day of visual contact with humans during rearing resulted in reduced avoidance behaviour of humans during adulthood and there was a trend for hens receiving positive handling to have a lower corticosterone response to human contact than those receiving negative handling. Visible human presence associated with predictable approach, human voice, slow movements and gentle handling for weighing, were effective in inducing habituation to humans in laying hens (Bertin et al 2019).…”