Narrative reviewindependent cross-checkabstract only checked★ key study I-INTA-06 in-depth review
What does oxytocin do in dairy cows?
Induction of milk ejection and milk removal in different production systems.
Overview
Bruckmaier RM et al.. Journal of animal science 2008 · PMID 17709779 · DOI 10.2527/jas.2007-0335
Oxytocin releases the milk stored in the udder during milking; long-term injections make cows respond less to their own oxytocin.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Physiology of milk let-down
- How was the study done?
Narrative review
- How many people, animals or samples were studied?
Not applicable
- What was actually found?
Oxytocin is needed to release most stored milk; chronic injections reduce natural responsiveness
- How large was the observed effect?
Not applicable
- What do the results mean in everyday life?
Oxytocin helps milk flow, it does not make a cow produce milk all year
- What are the study's limitations?
Review; abstract only
- What does it say about Elawady's specific claim?
Contradicts the mechanism he describes; supports that injections are problematic for the animal
- Do the results apply to Germany and Europe?
High
- What can explicitly not be concluded from this study?
How often the practice occurs in Egypt
Scientific in-depth review
1. Full reference
- Authors
- Bruckmaier RM et al.
- Journal
- Journal of animal science
- Year
- 2008
- Identifier
- PMID 17709779 DOI 10.2527/jas.2007-0335
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
How milk ejection and milk removal are induced in different production systems
3. Study design and population
- Study design
- Narrative review – Narrative review of milk ejection physiology
- Population
Dairy cows
- Country
Not applicable
- Period
Not applicable
- Sample size
Not applicable
- Inclusion and exclusion criteria
Not applicable
4. Methods and endpoints
- Exposure / intervention
Udder stimulation; endogenous and exogenous oxytocin
- Comparator
Not applicable
- Endpoints
Milk ejection, milk removal
- Statistical methods
Not applicable
5. Actual results
- Results
Milk ejection, needed to obtain the alveolar fraction (>80% of stored milk), is induced by oxytocin release after teat stimulation. Disturbed milk ejection is due to reduced or absent oxytocin release. Injecting exogenous oxytocin for an extended time reduces the mammary response to endogenous oxytocin.
- Absolute risks
Not applicable
- Authors' conclusion
In all milk production systems stress should be minimised and proper udder prestimulation performed.
6. Strengths
- Expert review by leading lactation physiologists
7. Weaknesses
- Narrative review
- Abstract only
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- not assessable
- Rationale
Narrative review.
9. Assessment of the statistical interpretation
Physiological description; not an outcome study.
10. Relevance to the specific claim
Clarifies that oxytocin's role is milk let-down, not maintaining lactation over the year; and that chronic exogenous oxytocin has drawbacks.
11. Independent contrary findings
Does not address the prevalence of oxytocin injection in Egypt.
12. Transferability to Germany and Europe
High (physiology is universal).
13. Overall methodological judgement
Reliable physiology background.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | not assessable |
| Precision of results | not applicable |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
None for this claim.
15. Linked fact checks
- Cows naturally lactate seasonally (after giving birth), but dairy cows are injected with oxytocin all year round so that they keep producing milk; such milk is 'induced, not real'. – Studies contradicting or limiting the claim