Long-Term and Transgenerational Effects of Stress Experienced during Different Life Phases in Chickens (Gallus gallus)

Abstract

Stress in animals causes not only immediate reactions, but may affect their biology for long periods, even across generations. Particular interest has been paid to perinatal stress, but also adolescence has been shown to be a sensitive period in mammals. So far, no systematic study has been performed of the relative importance of stress encountered during different life phases. In this study, groups of chickens were exposed to a six-day period of repeated stress during three different life phases: early (two weeks), early puberty (eight weeks) and late puberty (17 weeks), and the effects were compared to an unstressed control group. The short-term effects were assessed by behaviour, and the long-term and transgenerational effects were determined by effects on behavior and corticosterone secretion, as well as on hypothalamic gene expression. Short-term effects were strongest in the two week group and the eight week group, whereas long-term and transgenerational effects were detected in all three stress groups. However, stress at different ages affected different aspects of the biology of the chickens, and it was not possible to determine a particularly sensitive life phase. The results show that stress during puberty appears to be at least equally critical as the previously studied early life phase. These findings may have important implications for animal welfare in egg production, since laying hens are often exposed to stress during the three periods pinpointed here.

Effects of Maternal Stress on Measures of Anxiety and Fearfulness in Different Strains of Laying Hens

“…In accordance with previous research (25,41,90), the present study did not show an interaction between treatment and sex to affect measures of anxiety and fearfulness in the offspring. Nevertheless, the current study suggests that female chickens are more anxious than males, displaying a higher frequency of distress calls during TI and a similar trend pattern in SI.…”

“…Hens from the MS flocks were subjected to each of the following procedures: (1) Hens were equally distributed into two plastic crates (89 cm long × 60 cm wide × 26 cm high; 12 hens/crate), followed by 15 min of transportation [ Figure 2A, laying hen: (40)]. (2) Hens were individually removed from their home pens and placed inside a cloth bag located in a nearby room for 10 min of physical restraint [ Figure 2B, laying hen: (41)]. (3) Hens were crated into two groups of 12 birds, transported to an empty room 400 m away from their home pen and transferred to a test arena (100 cm long × 100 cm wide × 200 cm high) constructed of solid white panels with two doors located on opposite walls and two LED lights on the ceiling for 30 min.…”

Comparison of performance, health and welfare aspects between commercially housed hatchery-hatched and on-farm hatched broiler flocks

“…Because early-life stressors can have long-term effects on the development, performance and survival of chickens later in life (e.g., Decuypere et al, 2001, Elfwing et al, 2015, Ericsson et al, 2016, our hypothesis is that on-farm hatched chicks would show better performance compared to chicks hatched at the hatchery and transported to the broiler farm at day-old. In addition, we hypothesise that lower stress associated with on-farm hatching would improve welfare and health compared to hatchery-hatched chicks.…”

Acute stressors experienced by layer breeders do not affect measures of stress and fear in their offspring

“…Hens were equally distributed into 2 plastic crates (89 cm long × 60 cm wide × 26 cm high) (12 hens / crate), followed by 15 minutes of transportation (28); 2. Hens were individually removed from their home-pens and placed inside a cloth bag located in a nearby room for 10 minutes of physical restraint (29); 3. Hens were crated into 2 groups of 12 birds, transported to an empty room 400 m away from their home-pen and transferred to a test box (100 cm × 100 cm × 200 cm) constructed of solid white panels with 2 doors located on opposite walls and 2 LED lights on the ceiling for 30 minutes.…”