A meta-analysis on the effect of environmental enrichment on feather pecking and feather damage in laying hens
Bibliographic record
Abstract
Feather pecking (FP) is a significant issue in laying hens, which impacts societal acceptance of poultry farming, farm productivity, and bird welfare. Environmental enrichment-modifications of the environment to stimulate biological functioning and psychological well-being of animals-is one management strategy farmers can use to mitigate FP. However, inconsistent results of environmental enrichment are reported across studies questioning its value. A meta-analysis was used to determine the effect of environmental enrichment on FP and feather damage (FD) in laying hens. A systematic review of published literature from 4 databases resulted in 23 publications that met inclusion criteria. Feather pecking and FD outcomes were standardized between studies using different scoring systems. Driving variables included the presence of enrichment, production period when the enrichment started, housing type, beak trimming, bird strain, and age of the birds when FP and FD was measured. Considering the experiment as a random effect, linear mixed model analysis was used in a 2-step approach, whereby variables with a P < 0.30 in univariate analysis were included within the subsequent multivariate analysis. Variables with P < 0.05 in the multivariate analysis were retained in the final models. Model selection and evaluation were based on corrected Akaike information criteria, the root mean square prediction errors, and concordance correlation coefficients. A higher frequency of FP was observed in flocks lacking enrichment (P < 0.001), with increased age (P = 0.001), and in cage housing systems (P = 0.002). Similarly, FD increased in flocks lacking enrichment (P = 0.018), with increased age (P < 0.001), in the absence of beak trimming (P = 0.001) and in cage housing systems (P = 0.042). This meta-analysis confirmed the effectiveness of environmental enrichment in reducing FP and FD. Nevertheless, the modest ability of enrichment to dampen FD (-0.14 ± 0.06, 1-4 scale) suggests that other management strategies must be implemented in conjunction with environmental enrichment to successfully manage FP and resulting FD.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.008 | 0.023 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.012 | 0.040 |
| Bibliometrics | 0.005 | 0.005 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".