-->PONE-D-26-12173-->-->Determining optimal practices for foal weaning based on physiological, behavioural, and welfare indices – a protocol for a systematic review and network meta-analysis-->-->PLOS One

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PLOS One

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JL is a registered equine breeder with a financial stake in the industry. The remaining authors declare no financial competing interests.

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Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

1. Does the manuscript provide a valid rationale for the proposed study, with clearly identified and justified research questions?

The research question outlined is expected to address a valid academic problem or topic and contribute to the base of knowledge in the field.-->

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

-->2. Is the protocol technically sound and planned in a manner that will lead to a meaningful outcome and allow testing the stated hypotheses?

The manuscript should describe the methods in sufficient detail to prevent undisclosed flexibility in the experimental procedure or analysis pipeline, including sufficient outcome-neutral conditions (e.g. necessary controls, absence of floor or ceiling effects) to test the proposed hypotheses and a statistical power analysis where applicable. As there may be aspects of the methodology and analysis which can only be refined once the work is undertaken, authors should outline potential assumptions and explicitly describe what aspects of the proposed analyses, if any, are exploratory.-->

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

-->3. Is the methodology feasible and described in sufficient detail to allow the work to be replicable?

Descriptions of methods and materials in the protocol should be reported in sufficient detail for another researcher to reproduce all experiments and analyses. The protocol should describe the appropriate controls, sample size calculations, and replication needed to ensure that the data are robust and reproducible.-->

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

-->4. Have the authors described where all data underlying the findings will be made available when the study is complete?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception, at the time of publication. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.-->

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

-->5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.-->

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

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-->6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above and, if applicable, provide comments about issues authors must address before this protocol can be accepted for publication. You may also include additional comments for the author, including concerns about research or publication ethics.

You may also provide optional suggestions and comments to authors that they might find helpful in planning their study.

(Please upload your review as an attachment if it exceeds 20,000 characters)-->

Reviewer #1: Scientific Comments on the Review (Point-by-Point Evaluation and Suggested Corrections)

1. Line 77–84: Introduction – Contextualizing Equine Welfare Concerns

Comment:

The opening effectively establishes the societal and ethical context for improving equine welfare, citing relevant literature (e.g., Douglas et al., 2022; Heleski, 2023). However, the claim that "the horse industry faces increasing public pressure" would benefit from more specific data or survey-based evidence to substantiate the trend. Consider citing public opinion studies or reports from animal welfare NGOs (e.g., World Horse Welfare) to strengthen this assertion.

Suggested revision:

"Growing public scrutiny of equine welfare, evidenced by increased media coverage and consumer surveys (e.g., World Horse Welfare, 2023), has placed pressure on the industry..."

2. Line 79–81: Reference to 2021 Olympic Incident

Comment:

While the reference to the 2021 Olympic Pentathlon incident is accurate and impactful, the citation (Cuckson, 2021) appears to refer to a news report rather than a peer-reviewed source. For scientific rigor in a systematic review protocol, it is preferable to cite formal investigations or official reports (e.g., FEI inquiry outcomes) where available.

Suggested revision:

Replace with:

"...such as the 2021 Olympic Modern Pentathlon horse incident (FEI, 2021), which prompted widespread criticism and calls for reform."

3. Line 86–89: Broadening Scope to Weaning Practices

Comment:

This transition is logical and well-supported. The inclusion of Pearson and Douglas (2025) strengthens the argument that weaning falls within broader welfare concerns. However, ensure that this reference is not forward-dated relative to the current date (April 2026); if unpublished or in press, clarify its status appropriately.

4. Line 91–104: Definition and Stress of Weaning

Comment:

The definition of weaning as “nutritional separation” aligns with Latham and Mason (2008) and Henry et al. (2020), but could be expanded slightly to acknowledge behavioural and emotional components of dam-offspring bonding, which contribute to stress responses. This would enhance biological plausibility.

Suggested addition:

"Weaning involves not only nutritional separation but also disruption of a strong social bond, contributing to significant psychological stress in foals."

Also, consider clarifying that abrupt weaning often includes abrupt social separation, which compounds stress beyond nutrition alone.

5. Line 107–117: Heterogeneity in Gradual Weaning Definitions

Comment:

This is a critical and well-articulated point. The lack of standardised definitions for "gradual weaning" across studies significantly undermines comparability. To strengthen this section, explicitly define how your review will categorise gradual vs. abrupt weaning based on operational criteria (e.g., duration of separation phases, frequency of contact).

Suggested clarification in Methods:

Add under Interventions:

"Gradual weaning will be operationally defined as any protocol involving staged physical separation over ≥3 days, including partial-contact systems (e.g., fenceline weaning), while abrupt weaning refers to immediate and complete separation without prior acclimatisation."

6. Line 119–125: Additional Management Strategies

Comment:

The list of strategies (nannies, diet modification, later weaning, pharmacology) is comprehensive. However, grouping pharmacological interventions (e.g., anxiolytics) with management practices may conflate fundamentally different approaches—one modifies physiology, others modify environment. Consider distinguishing between management-based and medical/pharmacological interventions in analysis.

Suggestion:

In Data Items or Subgroups, classify interventions into categories:

• Environmental (housing, conspecifics)

• Temporal (age at weaning, weaning method)

• Dietary (pre-/post-weaning nutrition)

• Medical (pharmaceutical use)

This improves interpretability in NMA.

7. Line 130–140: Long-Term Consequences of Weaning Stress

Comment:

The paragraph convincingly links early-life stress to long-term developmental impacts. However, the citation of Valenchon et al. (2025) again raises concern about temporal validity (assuming current date is April 2026). If this work has not yet been published, it should be cited as "in press" or removed until verified.

Additionally, consider adding a sentence linking these long-term effects directly to economic and performance implications for breeders, enhancing translational relevance.

8. Line 156–165: Justification for Systematic Review and NMA

Comment:

Strong justification for using both pairwise and network meta-analysis. However, note that Bayesian NMA requires careful handling of multi-arm trials and assumptions about independence. Clarify whether multi-arm studies will be accounted for using appropriate methods (e.g., arm-based or contrast-based models with covariance adjustment).

Suggested addition in Methods:

"For multi-arm trials, correlations between effect estimates will be accounted for using arm-based models or variance-correction techniques to avoid unit-of-analysis errors."

9. Line 219–222: Timeline of Review Process

Comment:

Given that full-text screening is expected by July 2026 and submission by late 2027, the statement appears plausible. However, since the initial search was conducted in August 2025, confirm that a study update search will be performed immediately before final synthesis (as noted in line 339), particularly given the two-year gap.

Ensure this is clearly stated to maintain currency.

10. Line 240–261: Intervention Criteria

Comment:

Clear distinction between planned and unplanned weaning is appropriate. However, the exclusion of wild/feral populations is justified but could be nuanced—some feral studies (e.g., on mustangs or brumbies) provide valuable baseline data on natural weaning patterns. While excluded from quantitative synthesis, consider mentioning their value in supplementary discussion.

Reviewer #2: Review Comments to the Author

This manuscript presents a timely and relevant systematic review and network meta-analysis protocol on foal weaning practices. The study demonstrates strong methodological rigor, transparency, and adherence to PRISMA-P guidelines, with strengths including OSF registration, grey literature inclusion, and planned pairwise and Bayesian NMA.

However, several issues should be addressed before publication.

Major concerns:

The inclusion of diverse study designs (e.g., observational and case series) may introduce heterogeneity and bias; further justification and clarification of their role in synthesis are needed. The use of the Cochrane RoB v1 tool should be justified or updated to RoB 2. Outcome heterogeneity requires clearer strategies for harmonisation and prioritisation. The assumptions underlying NMA, particularly transitivity, need stronger justification and explanation of how violations will be handled. Additionally, the choice of Bayesian priors should be justified and supported with references.

Minor concerns:

The Introduction could be more concise, and tense should consistently reflect a protocol. The Google Scholar search limit requires justification. Consider reporting inter-rater reliability, clarifying subgroup definitions, and acknowledging limitations related to publication bias and language restrictions.

Overall, this is a well-designed and impactful protocol. With revisions to improve methodological clarity, it will be suitable for publication.

Recommendation: Major Revision

Reviewer #3: Major comments

1.Title: Shorten the title for readability;

2. Abstract: Clarify the type of study (protocol only) and explicitly state that no empirical results are included.

3.Confirm the OSF registration DOI (https://doi.org/10.17605/OSF.IO/DJWQY) is active and publicly accessible. Add a sentence confirming no protocol amendments beyond those already documented.

4.Standardize terminology: abrupt weaning and gradual weaning definitions are clear but should be formally defined in a single box or paragraph for consistency.

5.Explicitly state whether language is restricted to English (currently implied but not clearly stated).

6. Methods: Specify the exact six databases used (listed in Table 1 but not fully listed in the main text); In NMA: Clearly state the reference intervention (abrupt individual weaning) earlier in Methods; Define time-frame categories (immediate/short/medium/long-term post-weaning) in a table for quick reference.

Minor comments

1.Add a brief graphical abstract or flow diagram of review stages for readability.

2.Include a list of predefined primary/secondary outcomes in a table.

3.Specify planned software versions (R, RevMan, Covidence) if known.

Reviewer #4: It is a very detailed protocol for a systematic review and network meta-analysis. I do not see the need for any amendments.

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

**********

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Attachments

Attachment

Submitted filename: Scientific Comments on the Review.docx

Determining optimal practices for foal weaning – a protocol for a systematic review and network meta-analysis

PONE-D-26-12173R1

Dear Dr. Nicole Cranston,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Ewa Tomaszewska, DVM Ph.D

Academic Editor

PLOS One

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

1. Does the manuscript provide a valid rationale for the proposed study, with clearly identified and justified research questions?

The research question outlined is expected to address a valid academic problem or topic and contribute to the base of knowledge in the field.-->

Reviewer #2: Yes

Reviewer #3: Yes

**********

-->2. Is the protocol technically sound and planned in a manner that will lead to a meaningful outcome and allow testing the stated hypotheses?

The manuscript should describe the methods in sufficient detail to prevent undisclosed flexibility in the experimental procedure or analysis pipeline, including sufficient outcome-neutral conditions (e.g. necessary controls, absence of floor or ceiling effects) to test the proposed hypotheses and a statistical power analysis where applicable. As there may be aspects of the methodology and analysis which can only be refined once the work is undertaken, authors should outline potential assumptions and explicitly describe what aspects of the proposed analyses, if any, are exploratory.-->

Reviewer #2: Yes

Reviewer #3: Yes

**********

-->3. Is the methodology feasible and described in sufficient detail to allow the work to be replicable?

Descriptions of methods and materials in the protocol should be reported in sufficient detail for another researcher to reproduce all experiments and analyses. The protocol should describe the appropriate controls, sample size calculations, and replication needed to ensure that the data are robust and reproducible.-->

Reviewer #2: Yes

Reviewer #3: Yes

**********

-->4. Have the authors described where all data underlying the findings will be made available when the study is complete?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception, at the time of publication. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.-->

Reviewer #2: Yes

Reviewer #3: Yes

**********

-->5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.-->

Reviewer #2: Yes

Reviewer #3: Yes

**********

-->6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above and, if applicable, provide comments about issues authors must address before this protocol can be accepted for publication. You may also include additional comments for the author, including concerns about research or publication ethics.

You may also provide optional suggestions and comments to authors that they might find helpful in planning their study.

(Please upload your review as an attachment if it exceeds 20,000 characters)-->

Reviewer #2: The protocol addresses an important and timely topic in equine welfare, namely the identification and comparison of artificial weaning practices that may reduce stress and improve welfare outcomes in foals. The research questions are clearly stated and justified, and the protocol is generally well designed, methodologically rigorous, and aligned with current best-practice guidance for systematic reviews and network meta-analyses. Strengths of the protocol include a comprehensive search strategy, clearly defined eligibility criteria, independent screening and data extraction procedures, appropriate risk-of-bias assessment methods, and detailed plans for both pairwise meta-analysis and Bayesian network meta-analysis. The authors also appropriately consider important assumptions underlying network meta-analysis, including heterogeneity, transitivity, and coherence, and have proposed sensitivity analyses to assess the robustness of findings. The planned use of GRADE and CINeMA frameworks further strengthens the assessment of evidence certainty. The manuscript is generally well written, logically structured, and presented in clear academic English. The methods are described in sufficient detail to allow replication by other researchers, and the commitment to making study materials available through the Open Science Framework is commendable. I have only a few minor suggestions for improvement. First, the authors may wish to provide additional detail regarding which datasets, extracted data files, analytical code, and supplementary materials will be deposited in the OSF repository to further strengthen compliance with data-sharing requirements. Second, although formal power calculations are not typically feasible for systematic reviews and network meta-analyses because the available evidence base is unknown at the protocol stage, a brief acknowledgment of this limitation within the methods section would be helpful. Third, given the anticipated heterogeneity in weaning interventions and outcome measurements, the authors may consider providing additional justification for the planned categorisation of moderators and subgroup definitions.

Overall, this is a high-quality protocol addressing a relevant research question. The proposed methodology is appropriate, feasible, and likely to produce meaningful findings that will contribute to the evidence base on equine welfare and weaning management practices. Subject to minor revisions and clarifications, I believe the protocol is suitable for publication.

Reviewer #3: The authors had revised the manuscript according to reviewer's comments. The current vesion meet the standard of Plos One.

**********

-->7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review?  For information about this choice, including consent withdrawal, please see our Privacy Policy.-->

Reviewer #2: No

Reviewer #3: No

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