Chronic cyclic mild heat stress downregulates genes encoding muscle structural components, contributing to reduced breast muscle mass in broiler chickens with minimal impact on meat quality
Bibliographic record
Abstract
Heat stress (HS), whether constant or cyclic, poses a significant challenge to the poultry industry, leading to reduced performance, compromised animal welfare, and health issues. Despite its well-known effects, the specific impact of HS on muscle growth and development remains incompletely understood. This study investigated the effects of chronic cyclic mild HS on body weight (BW), breast muscle yield (BMY), meat quality, glycolytic metabolites, and gene expression in the breast muscles of finishing broilers. A total of 900 Ross 308 chicks (450 males and 450 females) were reared under thermoneutral (TN, n = 10 pens, 5 pens/sex, 45 birds/pen, 450 birds in total) or HS (n = 10 pens, 5 pens/sex, 45 birds/pen, 450 birds in total) conditions (30 °C, 45% RH for 10 h/d from days 28 to 34). On day 35, 2 birds per pen were sampled for meat quality and RNA-Seq analysis. HS reduced BW (P = 0.002) and Pectoralis major muscle yield (P = 0.02) and tended to decrease BMY (P = 0.06). Meat quality traits, glycolytic metabolites, and muscle protein functional properties were not affected (P > 0.05), likely due to compensatory feed intake before and after HS exposure. Transcriptomic analysis revealed 301 differentially expressed genes (DEGs), including 138 downregulated and 163 upregulated genes under HS (|Log2FC| > 1.0, P < 0.05). Several downregulated DEGs showed significant positive correlations with BW and muscle mass. Functional enrichment indicated these genes were involved in structural pathways, including extracellular matrix-receptor interaction, cytoskeleton organization in muscle cells, and regulation of the actin cytoskeleton. These pathways are essential for muscle integrity, growth, and repair. Our findings suggest a previously underexplored mechanism by which HS impairs broiler performance through disruption of structural gene networks critical for muscle development.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".