Effects of outdoor ranging on external and internal health parameters for hens from different rearing enrichments

Abstract

In Australia, free-range layer pullets are typically reared indoors, but adult layers go outdoors, and this mismatch might reduce adaptation in laying environments. Enrichments during rearing may optimise pullet development and subsequent welfare as adult free-range hens. In the outdoor environment, hens may have greater opportunities for exercise and natural behaviours which might contribute to improved health and welfare. However, the outdoor environment may also result in potential exposure to parasites and pathogens. Individual variation in range use may thus dictate individual health and welfare. This study was conducted to evaluate whether adult hens varied in their external and internal health due to rearing enrichments and following variation in range use. A total of 1386 Hy-Line Brown® chicks were reared indoors across 16 weeks with three enrichment treatments including a control group with standard housing conditions, a novelty group providing novel objects that changed weekly, and a structural group with custom-designed structures to increase spatial navigation and perching. At 16 weeks of age the pullets were moved to a free-range system and housed in nine identical pens within their rearing treatments. All hens were leg-banded with microchips and daily ranging was assessed from 25 to 64 weeks via radio-frequency identification technology. At 64–65 weeks of age, 307 hens were selected based on their range use patterns across 54 days up to 64 weeks: indoor (no ranging), low outdoor (1.4 h or less daily), and high outdoor (5.2–9 h daily). The external and internal health and welfare parameters were evaluated via external assessment of body weight, plumage, toenails, pecking wounds, illness, and post-mortem assessment of internal organs and keel bones including whole-body CT scanning for body composition. The control hens had the lowest feather coverage (p < 0.0001) and a higher number of comb wounds (P = 0.03) than the novelty hens. The high outdoor rangers had fewer comb wounds than the indoor hens (P = 0.04), the shortest toenails (p < 0.0001) and the most feather coverage (p < 0.0001), but lower body weight (p < 0.0001) than the indoor hens. High outdoor ranging decreased both body fat and muscle (both p < 0.0001). The novelty group had lower spleen weights than the control hens (P = 0.01) but neither group differed from the structural hens. The high outdoor hens showed the highest spleen (P = 0.01) and empty gizzard weights (P = 0.04). Both the rearing enrichments and ranging had no effect on keel bone damage (all P ≥ 0.19). There were no significant interactions between rearing treatments and ranging patterns for any of the health and welfare parameters measured in this study (P ≥ 0.07). Overall, rearing enrichments had some effects on hen health and welfare at the later stages of the production cycle but subsequent range use patterns had the greatest impact.

Rearing Enrichments Affected Ranging Behavior in Free-Range Laying Hens

“…The effectiveness of provided enrichments could be impacted by the degree of interaction that each hen specifically had with the enrichment objects and/or their perception of them (i.e., stimulating, stressful, benign). The correlations of range use between successive age periods indicate consistency in individual ranging patterns, which was found to have implications for some welfare measures of the hens in this study, although most hens were in relatively good condition at the end of the trial (41). Across the whole trial, ∼3% of the hens never went outside.…”

Minimal Effects of Rearing Enrichments on Pullet Behaviour and Welfare

“…Assessments of skeletal structure, [3], for example, may have detected greater impacts of the structural enrichments. Measurements from some of the hens from the current study towards the end of the production cycle (64 weeks of age) did show effects of rearing treatments in the degree of plumage coverage, with less coverage in the control hens [36]. Based on the results from the pullets, it may be that in all rearing treatments there were sufficient resources supporting good pullet development.…”

“…Thus, changes in organ weights may not be sensitive enough to detect the effects of stressors. Further measurements on the structural pullets throughout the flock cycle, as part of the larger project, will reveal any potential negative impacts of this specific type of enrichment, although dissections on adult hens at 65 weeks of age did not show any differences in relative right adrenal weights between hens from all rearing treatments [36].…”

Associations between welfare and ranging profile in free-range commercial and heritage meat-purpose chickens (Gallus gallus domesticus)

“…In Sasso, comb pecking wounds were in the present study positively associated with walking difficulty, which may suggest that comb pecks are directed toward weaker individuals, not only socially but also physically. Better comb condition was recently found in laying hens provided with the free-ranging area ( Bari et al., 2020 ). We suspect that comb pecks observed in Sasso birds could also have a genetic background, while our study did not confirm that frequency of outdoor use may be beneficial.…”