Fearfulness in Commercial Laying Hens: A Meta-Analysis Comparing Brown and White Egg Layers

The influence of genetic strain on fear and anxiety responses of laying hens housed in a cage-free environment

Cage-free environments provide more behavioral opportunities for hens than cages, but fear responses in such open housing can lead to injuries and challenging human-animal interactions. This study evaluated the impact of genetic strain on fear and anxiety responses in two brown and one white genetic strain of laying hens: Hy-Line Brown (HB), Bovan Brown (BB), and H&N White (HN). Hens were assessed at the start of lay and peak lay through the inversion and attention bias tests, along with thermal imaging and core body temperature measurements to assess stress-induced hyperthermia. During the inversion test, HB hens performed significantly more wing flaps than other strains (p=0.012), while BB hens exhibited more vocalizations than HN hens (p=0.0041). Thermal imaging revealed that at the start of lay, HB and HN hens had higher maximum comb temperatures than BB hens (p<0.0001), but HB hens had lower temperatures at peak lay (p=0.027). BB and HN hens had higher core body temperatures at 4- and 5-minutes post-inversion (p<0.0001). In the attention bias test, HB and BB hens were more likely to resume eating and showed increased head bobbing as they aged, whereas HN hens were less likely to resume eating but maintained high head bobbing (p=0.017; p=0.00056). BB hens had the lowest average eye and maximum comb temperatures 3.5 to 4.5 min post-startle at the start of lay (p<0.05), white HN hens had the highest average eye and comb temperatures (p<0.0001) and higher average eye temperatures than BB at peak lay (p=0.026). Finally, HN hens had higher core body temperatures than HB hens at both the start of lay and peak lay (p=0.041; p=0.046). These results indicate that brown and white strains differ in their responses to fear and anxiety, with brown strains being more behaviorally responsive and white strains showing greater physiological stress. These strain-specific coping mechanisms provide insight into how hens may react to stressors in cage-free environments, aiding in strain selection for producers.

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.

Effects of Housing Systems on Production Performance, Egg Quality, Tonic Immobility and Feather Score in Laying Hens

BACKGROUND

This study was designed to investigate the effects of different housing systems on production performance, egg quality and welfare in laying hens.

METHODS

One hundred and twenty 42-week-old "Atak S" laying hens, purchased from a manufacturing company, were randomly assigned to 4 housing systems: conventional cages, furnished cages, deep-litter system and free-range. Each system housed 30 hens, which were kept in these systems for 6 weeks. Parameters regarding production performance, egg quality, plumage condition scores and tonic immobility were assessed at the end of the housing period.

RESULTS

Egg production and egg mass were lower in cage-free rearing systems than in caged systems. Mean egg weight in free-range hens, and albumen height and Haugh unit in deep-litter hens, were lower than in other housing systems. Eggshell weight in hens housed in furnished cages was greater than in free-range hens, while eggshell strength was better compared to that of hens in conventional cages. The housing system did not impact fearfulness; however, the deep-litter housing increased the sensitivity to touch or capture. Whole body and regional plumage condition scores of free-range hens elicited more favourable results than those kept in conventional cages. Because the plumage condition indicates welfare, the results proved the superiority of free-range over conventional rearing regarding welfare.

CONCLUSIONS

Concerning the parameters, such as egg production, animal welfare and fear level, overall data revealed the pros and cons of all housing systems investigated. We consider that this study's findings might contribute to the researchers and breeders seeking alternative housing for laying hens.

Raising laying hens: housing complexity and genetic strain affect startle reflex amplitude and behavioural response to fear-inducing stimuli

Individual variation in fearfulness can be modified during ontogeny, and high levels of fear can affect animal welfare. We asked whether early-life environmental complexity and genetic strain affect fear behaviour in young laying hens (pullets). Four replicates of brown (B) and white (W) genetic strains (breeds) of layers were each raised in four environmental treatments (housing): conventional cages (Conv) and different rearing aviaries with increasing space and complexity (Low < Mid < High). We used a startle reflex test (weeks 4 and 14) to measure startle amplitude and autonomic response (i.e. comb temperature). A combination of novel arena (NA) and novel object (NO) tests was used (week 14) to assess NA exploration and alertness, latency to approach the centre and initial NO avoidance and investigation. Housing × strain affected startle amplitude (B-Conv, B-High < B-Low, B-Mid; B > W; no housing effect in W) but not autonomic response. Fear behaviour was affected by housing (NA exploration, investigation: Conv < Low, Mid, High; NO avoidance: Conv, High < Low, Mid), strain (NA alertness: B > W, NO avoidance: W > B) and their interaction (NA centre approach: B-Conv < all other groups). We present evidence for strain-specific fear responses depending on early experience.

Daylight exposure and circadian clocks in broilers: part I-photoperiod effect on broiler behavior, skeletal health, and fear response

The aim of this study was to examine effects of various daylight exposure during the 24-h light-dark (L-D) cycle on growth performance, skeletal health, and welfare state in broilers. Environmental photoperiod and related circadian clock, the 24-h L-D cycle, are important factors in maintaining productive performance, pathophysiological homeostasis, and psychological reaction in humans and animals. Currently, various lighting programs as management tools for providing a satisfactory environmental condition have been used in commercial broiler production. Four hundred thirty-two 1-day-old Rose 308 broiler chicks were assigned to 24 pens (18 birds/pen). The pens were randomly assigned to 1 of 4 thermal and lighting control rooms, then the birds were exposed to (n = 6): 1) 12L, 2) 16L, 3) 18L, or 4) 20L at 15 d of age. Lighting program effects on bird body weight, behavioral patterns, bone health, and stress levels were evaluated from d 35 to d 45, respectively. The birds of 12L as well as 16L groups, reared under short photoperiods close to the natural 24-h L-D cycle, had improved production performance, leg bone health, and suppressed stress reaction compared to the birds of both 18L and 20L groups. Especially, 12L birds had heavier final body weight and averaged daily weight gain (P < 0.05), higher BMD and BMC with longer and wider femur (P < 0.05), lower H/L ratio (P < 0.05), and more birds reached the observer during the touch test (P < 0.05) but spent shorter latency during the tonic immobility test (P < 0.05). Taken together, the data suggest that supplying 12 h as well as 16L of daily light improves performance and health while decreasing stress levels in broilers, making it a potentially suitable approach for broiler production.

How are they really doing? Animal welfare on organic laying hen farms in terms of health and behaviour

1. The present study describes the current welfare situation on commercial organic laying hen farms in Sweden in terms of indoor environment, bird health and behaviour.2. Organic laying hen farms (n = 11) in Sweden were visited for one day each. The farm visits were performed at the end of lay and involved farmer interviews, indoor environment assessments, behavioural observations and tests and clinical examinations in one flock per farm.3. In 95% of all human avoidance distance test trials performed, the hens distanced themselves from the observer before the test was completed. Median number of birds per flock approaching during a novel object test (n = 4 trials per flock) was 2 (0-9). These results may indicate a high level of fear of humans and general fearfulness among the hens.4. Plumage damage was especially prevalent and most severe on the breast and belly, tail and wings, with median prevalence of moderate-severe damage of 96% (84-100), 96% (72-100) and 98% (94-100), respectively. Median prevalence of keel bone deviations was 67% (32-84) with 3% fractures (0-8). Median prevalence of breast skin lesions was 57% (10-74). There was a significant positive association between breast skin lesions and keel bone deviations (P = 0.02) and foot pad hyperkeratosis (P < 0.001). Median prevalence of severe hyperkeratosis was 33% (8-96), with prevalence being significantly lower where litter depth was thicker (P = 0.003). More dust bathing events were observed in flocks where litter depth was thicker (P = 0.007).5. The present study contributes with updated knowledge of laying hen welfare on organic farms in Sweden. The results confirm the findings of previous on-farm studies, demonstrating that important issues, including keel bone damage and severe feather pecking, remain in need of attention to ensure the welfare of laying hens in future commercial egg production.