The Effect of Rearing and Adult Environment on HPA Axis Responsivity and Plumage Condition in Laying Hens

The hypothalamic-pituitary-adrenal (HPA) axis responsivity is influenced by early life experience and also modified by the environment an individual experiences as an adult. Because laying hens are transferred from rearing to laying farms at 16-18 weeks of age, they are well suited to study the interaction effect between early (rearing) and adult (laying) environments on physiology and behaviour. In the European Union, there is a move towards cage-free systems for laying hens, but globally, the majority of layers are kept in conventional or furnished cages. Conventional cages have no enrichment, whereas furnished cages have little enrichment. Both cage types limit the movement of birds and the expression of highly motivated behaviours. Lack of enrichment may lead to under-stimulated birds that are more sensitive to stress and fear-inducing challenges later in life. Fearfulness has been linked to feather pecking, which has negative consequences for animal welfare and productivity. Previous research has shown that birds reared in cages are more fearful and perform more poorly in a test of spatial cognition than birds reared in aviaries when tested within five weeks after transition to adult housing. However, recent results suggest that these effects might not be long-lasting. We, therefore, tested the effect of the early (rearing) (aviary vs. cage) and adult (laying) environments (standard vs. additionally enriched furnished cages) on the corticosterone response to restraint in birds that were 35 weeks into lay (i.e., 52 weeks of age) and assessed their plumage condition. We hypothesised that a lower level of enrichment, both during rearing and adulthood, would represent a lower level of stimulation, resulting in a stronger corticosterone response to restraint and poorer feather cover. Both stressed (restrained) and control birds increased their corticosterone levels from the first (baseline) to second sample (p < 0.01 for both), but the increase in the restrained group was significantly higher than in the control group (F1, 111 = 9.51; p = 0.003). There was no effect of the early environment, but birds housed in standard furnished cages as adults had overall higher corticosterone levels than birds housed in enriched furnished cages regardless of their early life environment (F1, 51 = 4.12; p = 0.048). Neither early nor adult housing influenced the feather score except for on the belly, where birds housed in enriched cages as adults had a poorer feather score, contrary to our prediction. In conclusion, no effect of the early environment on HPA axis responsivity to an acute stressor could be detected at 52 weeks of age, but adult enrichment had a favourable effect on overall corticosterone levels.

[Preoperative parathyroid ultrasonography. 45 recent verified cases]

In a series of 45 patients operated upon for primary hyperparathyroidism, a total of 167 parathyroid glands were confirmed. Thirty out of the 43 parathyroid masses potentially accessible to ultrasounds were correctly identified by preoperative cervical ultrasonography. There were 124 true negative results, including one retro-oesophageal mass and one mediastinal mass, 1 false-positive result and 11 false-negative results, giving the method a sensitivity of 73% and a specificity of 99%. Sensitivity increases with the experience of the operator. The main factors that reduce sensitivity are change of apparatus, old age of the patient, small masses (less than 500 mg) and coexistence of a thyroid disease (22% of the cases). The ease with which parathyroid masses can be correctly identified is independent from plasma calcium and parathyroid hormone values.

Chickens perceive humans as social buffers and may follow human-given cues: A pilot study

Positive perception of humans, extensively documented in domestic mammals, remains comparatively underexplored in domestic birds like chickens, with existing studies largely focusing on fear reduction. This research evaluated whether chickens perceive humans positively, accounting for interaction types and breed differences. Two breeds (Lohmann LSL Classic, Brown Classic) experienced physical contact (PC), visual-only contact (VC), or minimal human contact (MC) over 13 days (Days 35-51; PC and VC: 1-2 min/day). Birds were assessed using three behavioral tests. During the separation-reunion test (Days 52-53), individuals underwent two 3-min separations (experimenter absent) and reunions (experimenter present) in an open-field setting. Subsequently, the experimenter attempted up to six standardized capture attempts to catch the birds (the capture test). Lastly, the local enhancement test (Days 120-137) assessed birds' ability to use human presence/gestures to locate food. In the separation-reunion test, PC birds exhibited calmer/positive behaviors, such as reduced vigilance and increased foraging, in the presence of the experimenter compared to being alone. Conversely, MC birds displayed fewer calm behaviors and greater withdrawal when the experimenter was present. Brown birds showed more calm behaviors, reduced movement, and spent more time near the experimenter than white birds. The capture test supported these results, with PC and brown birds being easier to capture. In the local enhancement test, two PC individuals and the brown PC group as a whole successfully used human-given cues to locate food rewards. These results indicate that, as observed in other species, chickens-especially those with positive human experiences-can associate humans with rewarding outcomes. Positive interactions may also lead chickens to perceive humans as social buffers-that is, as factors that help mitigate stress in challenging situations. Although fundamental, this study highlights the potential of breed-sensitive approaches to improve poultry welfare and opens the discussion on adapting human-animal interactions to breed-specific characteristics. These insights can inform welfare-enhancing practices and provide practical tools for on-farm management that benefit both animals and farmers.