Animal studyindependent cross-checkabstract checked I-CHK-110 standard review
An antibiotic feed additive increased woody breast in a trial
Bacitracin, Bacillus subtilis, and Eimeria spp. challenge exacerbates woody breast incidence and severity in broilers.
Overview
Jia L et al.. Poult Sci 2022 · PMID 34788711 · DOI 10.1016/j.psj.2021.101512
Bacitracin, a probiotic and a parasite challenge each increased woody breast in some conditions.
Does the study support the specific claim? Partly · Methodological quality: low
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Do management factors (antibiotic, probiotic, coccidial challenge) affect WB incidence?
- How was the study done?
Randomised factorial feeding trial in broilers (3 diets x cocci challenge x sex)
- How many people, animals or samples were studied?
not stated in abstract
- What was actually found?
Cocci challenge increased WB incidence on d 29 and d 43. Bacitracin increased early growth rate (d 0-14). In unchallenged birds, both the antibiotic and the probiotic diets increased WB incidence on d 43 (P = 0.040). Males had higher WB incidence.
- How large was the observed effect?
Cocci challenge increased WB incidence on d 29 and d 43. Bacitracin increased early growth rate (d 0-14). In unchallenged birds, both the antibiotic and the probiotic diets increased WB incidence on d 43 (P = 0.040). Males had higher WB incidence.
- What do the results mean in everyday life?
Things that push growth can make woody breast more common.
- What are the study's limitations?
Sample size not in abstract; WB assessed by palpation; Probiotic had a similar effect, so the link is not antibiotic-specific
- What does it say about Elawady's specific claim?
Gives partial support to an antibiotic role, but via growth, not as a specific cause.
- Do the results apply to Germany and Europe?
EU bans antibiotic growth promoters; finding has limited relevance for legal EU production.
- What can explicitly not be concluded from this study?
Cannot show that antibiotics are the main cause in practice.
Scientific in-depth review
1. Full reference
- Authors
- Jia L et al.
- Journal
- Poult Sci
- Year
- 2022
- Identifier
- PMID 34788711 DOI 10.1016/j.psj.2021.101512
- Verification
- verified – PubMed efetch 2026-10-26; Crossref 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Do management factors (antibiotic, probiotic, coccidial challenge) affect WB incidence?
3. Study design and population
- Study design
- Animal study – Randomised factorial feeding trial in broilers (3 diets x cocci challenge x sex)
- Population
Ross x Ross 708 broiler chicks
- Country
USA
- Period
not stated
- Sample size
not stated in abstract
- Inclusion and exclusion criteria
as described in the abstract
4. Methods and endpoints
- Exposure / intervention
Bacitracin 6.075 mg/kg feed; Bacillus subtilis probiotic; live cocci vaccine challenge
- Comparator
Basal diet without additives
- Endpoints
Growth, WB incidence by palpation
- Statistical methods
as reported in the abstract
5. Actual results
- Results
Cocci challenge increased WB incidence on d 29 and d 43. Bacitracin increased early growth rate (d 0-14). In unchallenged birds, both the antibiotic and the probiotic diets increased WB incidence on d 43 (P = 0.040). Males had higher WB incidence.
- Absolute risks
not reported
- Authors' conclusion
Bacitracin and Eimeria spp. increased WB incidence, body weight and growth rate.
6. Strengths
- Randomised design
7. Weaknesses
- Sample size not in abstract
- WB assessed by palpation
- Probiotic had a similar effect, so the link is not antibiotic-specific
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Animal trial; abstract only.
9. Assessment of the statistical interpretation
Suggests that growth-promoting interventions in general (not only antibiotics) can increase WB.
10. Relevance to the specific claim
Only located trial linking an antibiotic growth promoter to woody breast.
11. Independent contrary findings
12. Transferability to Germany and Europe
13. Overall methodological judgement
Bacitracin, a probiotic and a parasite challenge each increased woody breast in some conditions.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | low |
| Risk of bias | some concerns |
| Precision of results | low |
| Directness | indirect |
| Reproducibility | not replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
15. Linked fact checks
- Because of intensive production, modern chicken breast has become 'like wood' (woody breast). – Studies with mixed or unclear results