Review Reports - The Impact of Eggshell Thickness on the Qualitative Characteristics of Stored Eggs Produced by Three Breeds of Laying Hens of the Cage and Cage-Free Housed Systems

Round 1

Reviewer 1 Report

The submitted article for review corresponds to the subject of the authoritative scientific journal Applied Sciences (ISSN 2076-3417)

Type Article

Title The relationship between eggshell thickness and other quality features of eggs produced by the cage and cage-free housed laying hens

applsci-2024451

Dear authors:

A good scientific work of the publication is presented.

The title is good and quite specific and attracts the reader's interest so that it is easy to understand.

The topic of scientific research is quite interesting and relevant.

The scientific article is logically built, corresponds to the principles of presenting scientific information and research.

I think that the article used enough tables and illustrations.

There are some minor suggestions:

Abstract:

I recommend authors to expand, increase the number of words. This is necessary for readers to pay more attention to these studies.

keywords

I suggest adding a few terms to expand the search

Introduction

I encourage authors to present the goals and objectives of your research (clearly, concisely, and clearly).

In this section, I would recommend reviewing the regulatory documents on establishing requirements for: quality characteristics of chicken eggs, conditions and periods of storage of chicken eggs (levels: national, European, international), in accordance with the goals and objectives of your study.

Materials and Methods

I recommend specifying the methodology for selecting chicken eggs. Preparation of an average sample (selection for research).

L92 ... how the air temperature and natural air humidity were controlled. What changes occurred during the entire period of research (including during the day).

L19 .... How many chicken eggs were tested at each stage of characterization? Sampling technique for creating an "average sample".

Requires clarification information

Results

The authors of the scientific article present Sufficient interesting data. This is the starting point for discussion in this study.

The decrease between shell thickness and strength is also influenced by other characteristics, in particular the size and shape of the egg. The smaller or rounder the egg, the steeper the curvature (archedness) of its shell and, therefore, ceteris paribus, it turns out to be stronger. ??? The authors studied the following characteristics: the size and shape of a chicken egg for all groups of chickens.???

Impact, as you know, has a destructive force hundreds of times greater than pressure. In this regard, the most effective way to assess the strength of the shell is to test the eggs for impact or impact. The method is directly related to the production of eggs, which is its practical value. The simplest and most affordable way to evaluate eggs for shell strength is their pairwise impact. ??? did the authors conduct such studies?

Figure 2 ... how were the results obtained from individual specimens extended to the entire batch of chicken eggs selected for the study?

Figure 3 needs to be completed. Why is only one prototype reported (eggs of DeKalb laying hens aged 42 weeks and housed under cage-free249conditions.)?

Figures 4-9… for a better visualization of the presented data, it is possible to present it in a different form, for example, the Dynamics of changes for individual groups of chickens, and for control dates. I propose to create each figure (4-9) from four diagrams (for individual groups of chickens) ... I think thanks to this, the dependence will be quite clearly visible for the entire period of your observations. This is a recommendation.

Discussion

It has not been analyzed deeply enough.

The section needs substantial revision.

Conclusions

Monitoring shell strength will help identify the causes of losses from increased production losses and will help minimize these losses at different stages of the life cycle of chicken eggs (from the poultry farm to the final consumer of the product) It is necessary to significantly supplement and expand in accordance with the purpose and objectives of the research

It is necessary for the authors to significantly supplement and expand this section, in accordance with the purpose and objectives of the research

References

I note that the authors of the manuscript of the article approached the analysis of the problem quite carefully and used the necessary number of sources of information. From the presented list - more than 48 percent were published in the last 5 years.

However, it is necessary to supplement the list with publications concerning the storage of chicken eggs and other issues after updating the Introduction section.

I recommend the authors to make adjustments to the list of citing publications (References) and arrange them in accordance with the established style and rules. There are too many design inaccuracies.

I recommend for publication the scientific Article « The relationship between eggshell thickness and other quality features of eggs produced by the cage and cage-free housed laying hens» - applsci-2024451 after the comments have been corrected.

Author Response

The submitted article for review corresponds to the subject of the authoritative scientific journal Applied Sciences (ISSN 2076-3417)

Type Article

Title The relationship between eggshell thickness and other quality features of eggs produced by the cage and cage-free housed laying hens

applsci-2024451

Dear authors:

A good scientific work of the publication is presented.

The title is good and quite specific and attracts the reader's interest so that it is easy to understand.

The topic of scientific research is quite interesting and relevant.

The scientific article is logically built, corresponds to the principles of presenting scientific information and research.

I think that the article used enough tables and illustrations.

A: Dear reviewer. The authors thank you for carefully checking our manuscript and valuable comments. In preparing the manuscript authors have incorporated most of the changes suggested. The authors refer to them in detail below.

There are some minor suggestions:

Abstract:

R: I recommend authors to expand, increase the number of words. This is necessary for readers to pay more attention to these studies.

A: Dear reviewer. In preparing a manuscript for submission to the journal Applied Sciences, the authors were guided exclusively by the guidelines for authors. These guidelines emphasize that the Abstract section “should be 200 words maximum”. Unfortunately, we have already exceeded the allowed limit in words. Additional text will overload this section and make it hard to read. We would ask the reviewer to retain this section without any modification. Thank you!

R: keywords

I suggest adding a few terms to expand the search

A: Dear reviewer. The same holds for keywords. The authors believe the keywords chosen, along with their amount, are enough to understand the essence of the present work.

R: Introduction

I encourage authors to present the goals and objectives of your research (clearly, concisely, and clearly).

A: Dear reviewer. Such information is already presented in the manuscript's Introduction section: "The presence of a denser and thicker eggshell membrane and the eggshell itself promotes the delay of water movement across the shell and prevents dehydration of the egg interior components. Following the hypothesis, the study aimed to investigate eggshells' morphology and structural features derived from hens of three laying breeds and draw a line between their thickness and physical-chemical properties change during 36 days of storage."

R: In this section, I would recommend reviewing the regulatory documents on establishing requirements for: quality characteristics of chicken eggs, conditions and periods of storage of chicken eggs (levels: national, European, international), in accordance with the goals and objectives of your study.

A: Dear reviewer. The ‘best before’ of table eggs defined by the EC regulations No 589/2008 at ambient temperature and relative air humidity of 50% is defined as 28 days after the laying date. Unfortunately, no direct comparison of egg shelf-life between the countries (outside the EU) can be made due to differences in storage conditions. For instance, according to the United States Department of Agriculture regulation, the shelf-life of eggs is defined as 3-5 weeks under refrigerated conditions after being laid (https://ask.usda.gov/s/article/How-long-can-you-store-eggs-in-the-refrigerator), while for room temperature there is no such information. Unfortunately for other countries, we could not find regulations (normative acts) that would indicate the expiration date of shell eggs. The authors have provided additional references and discussion regarding this matter (highlighted in red). Thank you very much for your point.

R: Materials and Methods

I recommend specifying the methodology for selecting chicken eggs. Preparation of an average sample (selection for research).

L92 ... how the air temperature and natural air humidity were controlled. What changes occurred during the entire period of research (including during the day).

L19 .... How many chicken eggs were tested at each stage of characterization? Sampling technique for creating an "average sample".

Requires clarification information

A: Dear reviewer. The authors apologize for not providing a detailed description of the methodology of collecting chicken eggs. We have revised and supplemented the description of eggs sampling and hope this is sufficient: To evaluate egg physical-chemical properties change as a function of storage time, 180 eggs from each hen breed were collected within four hours of being laid. Collected eggs were packed individually per 16 pc in cardboard packaging with a perforated lid. The total number of harvested eggs amounted to 720 eggs. At the initial stage of storage, 16 eggs from each group were taken and immediately delivered to the laboratory of JSC "Balticovo" for the initial screening of quality attributes. At the same time, the remaining part of the eggs was placed in a humidity and temperature-controlled storage room for subsequent storage. The eggs were stored under controlled conditions at 20 °C with 50% relative air humidity. The length of the experiment was 36 days. To elucidate the changes in quality indicators, eggs' physical-chemical properties were analyzed once every four days, i.e., 1, 4, 8, etc. (except for 8–11, 11–15, and 15–18 days) during 36 days of storage. In the successive days of storage, 16 eggs per breed were taken to ensure an average sample.

R: Results

The authors of the scientific article present Sufficient interesting data. This is the starting point for discussion in this study.

R: The decrease between shell thickness and strength is also influenced by other characteristics, in particular the size and shape of the egg. The smaller or rounder the egg, the steeper the curvature (archedness) of its shell and, therefore, ceteris paribus, it turns out to be stronger. ??? The authors studied the following characteristics: the size and shape of a chicken egg for all groups of chickens.???

A: Dear reviewer. The authors are grateful for the reasonable concern regarding the size and shape of the eggs selected. However, the authors want to stress that no substantial differences were observed in these parameters between selected eggs. To ensure the reliability of the results, the eggs were purposefully collected with the same size and shape. The size of the eggs corresponded to size M, with an average weight of 59 ± 3 grams.

R: Impact, as you know, has a destructive force hundreds of times greater than pressure. In this regard, the most effective way to assess the strength of the shell is to test the eggs for impact or impact. The method is directly related to the production of eggs, which is its practical value. The simplest and most affordable way to evaluate eggs for shell strength is their pairwise impact. ??? did the authors conduct such studies?

A: Dear reviewer. The authors are thankful for sharing this valuable information regarding the analysis of breaking strength. We will take this into account in our future experiments. Thank you! However, this research used quasi-static compression to directly measure eggshell-breaking strength. For this purpose, the authors used the FUTURA Egg-Shell-Tester V. 2.0 (Lohne, Germany) tester equipped with an aluminium compression disc 7.62 cm in diameter attached to the unit and an egg holder. We placed the egg between two discs of the equipment and applied force until the egg was broken.

R: Figure 2 ... how were the results obtained from individual specimens extended to the entire batch of chicken eggs selected for the study?

A: Dear reviewer. The authors are grateful for the reasonable question regarding the results obtained in this experiment and how these results could be extrapolated to the entire batch. To make this experiment more reliable at the initial stage, we selected ten eggs from each group of breeds. In general, we had 40 samples. For each egg sample of the particular group, we prepared five specimens for SEM analysis. Overall, we made 50 measurements of a particular group. We understand that the reviewer may find this data inadequate, but we were limited in resources; therefore, we were forced to restrict ourselves to 50 measurements.

R: Figure 3 needs to be completed. Why is only one prototype reported (eggs of DeKalb laying hens aged 42 weeks and housed under cage-free conditions.)?

A: Dear reviewer. The authors understand the concern of the reviewer. However, the EDS mapping analyses of the entire eggshell from four egg samples revealed similar profiles and compositions of elements. In general, six base elements, i.e., Na, Mg, P, S, Ca, and O, were detected in the eggshell. Following limitations in space, we found it irrational to show the same results four times.

R: Figures 4-9… for a better visualization of the presented data, it is possible to present it in a different form, for example, the Dynamics of changes for individual groups of chickens, and for control dates. I propose to create each figure (4-9) from four diagrams (for individual groups of chickens) ... I think thanks to this, the dependence will be quite clearly visible for the entire period of your observations. This is a recommendation.

A: Dear reviewer. The authors are grateful for this proposal. We attempted to present the results on dynamics in a different shape but got figures even worse representative than using histograms. Therefore, we ask you to retain these figures without any modifications. Thank you!

R: Discussion

It has not been analyzed deeply enough.

The section needs substantial revision.

A: The discussion section is combined with the results.

R: Conclusions

It is necessary for the authors to significantly supplement and expand this section, in accordance with the purpose and objectives of the research

A: Dear reviewer. The authors are grateful for the remark. However, as it seems, we touched on all the research findings, and the essence of the research has been indicated in this section. The main intention of the present work was to confirm or deny the hypothesis that the presence of a denser and thicker eggshell membrane and the eggshell itself promotes the delay of water movement across the shell and prevents dehydration of the egg interior components. The hypothesis was denied since the results indicated that the quality of eggs was found to be storage time-dependent, and the rate of their deterioration was primarily associated with the genetic background of laying hens and their housing conditions rather than with the structure of the eggshell. Unfortunately, we have nothing more to add.

R: References

However, it is necessary to supplement the list with publications concerning the storage of chicken eggs and other issues after updating the Introduction section.

A: Dear reviewer. Thank you very much for the positive evaluation. We have reviewed the reference list and made the necessary amendments and supplementations. Thank you very much.

R: I recommend for publication the scientific Article « The relationship between eggshell thickness and other quality features of eggs produced by the cage and cage-free housed laying hens» - applsci-2024451 after the comments have been corrected.

A: Dear reviewer. The authors thank you for carefully checking our manuscript and valuable comments.

On behalf of all the co-authors

Yours sincerely,

Vitalijs Radenkovs

Principal investigator, Latvia University of Life Sciences and Technologies, Research Laboratory of Biotechnology, Division of Smart Technologies.

Reviewer 2 Report

Dear Authors,

I would like to congratulate you for conducting such an interesting study to explore the relationship between egg quality produced by different hens during storage. I have certain suggestions to further improve the quality of the manuscript as mentioned below.

1. Manuscript's language needs slight improvement. L 55, what does it mean "marriage sorted out", L 67-68, rewrite for better understanding.

L 91, It should be 4 h.

L447, Is it Cu or Ca?

L454-455, rewrite this sentence for better understanding.

Recheck whole manuscript for similar corrections.

2. It is suggested to clearly mention the novelty of your work before stating the objective in introduction section.

3. The manuscript's title doesn't clearly reflect the study's objective (L 82-84). I suggest to change the title of your study to "Impact of breed and housing condition of laying hens on quality of their eggs and eggshell thickness during storage".

Author Response

R: Dear Authors,

A: Dear reviewer. The authors would like to thank you for carefully checking our manuscript and valuable comments. In preparing the manuscript authors have incorporated most of the changes suggested. The authors refer to them in detail below.

R: Manuscript's language needs slight improvement. L 55, what does it mean "marriage sorted out"

A: Dear reviewer. The authors are sorry for such typos. We intended to say “flaw / defects” This shortcoming has been corrected. Thank you.

R: L 67-68, rewrite for better understanding.

A: The authors are grateful for your valuable remark. This sentence has been reworked.

R: L 91, It should be 4 h.

A: The authors are grateful for your valuable remark. This shortcoming has been corrected.

R: L447, Is it Cu or Ca?

A: Dear reviewer. The authors are grateful for your question. In answering to your question, the authors want to highlight the work of Qiu et al. where the authors stressed that exactly the availability of Cu (copper) in the diet of hens makes the eggshell membrane more rigid and thick. This is due to role of this element in the modulation of crucially essential enzymes involved in the formation of eggshell membrane.

Qiu, J. L.; Zhou, Q.; Zhu, J. M.; Lu, X. T.; Liu, B.; Yu, D. Y.; Lin, G.; Ao, T.; Xu, J. M. Organic trace minerals improve eggshell quality by improving the eggshell ultrastructure of laying hens during the late laying period. Poult. Sci. 2020, 99, 1483–1490, doi:10.1016/j.psj.2019.11.006.

R: L454-455, rewrite this sentence for better understanding.

A: Dear reviewer. This sentence has been corrected. Thank you.

Eggs obtained from cage-free housed hens H/D/BWE showed the most significant weight loss, and eggs from the cage and cage-free housed hens H/LS/CCE and H/HN/BCE the lowest, respectively.

R: Recheck whole manuscript for similar corrections.

A: We have gone through the entire manuscript and double checked the text to reduce the number of typos and shortcomings. Thank you.

R: It is suggested to clearly mention the novelty of your work before stating the objective in introduction section.

A: Dear reviewer. Thank you very much for your remark. We have substantially reworked this section to make it easy to understand:

The limited information on the factors that, apart from storage conditions, could facili-tate egg ageing during storage [16,17] promoted the design of this study, focusing on the evaluation of the eggshell thickness produced by laying hens under conventional and cage-free housed systems. It is hypothesized that the presence of a denser and thicker eggshell membrane and the eggshell itself could contribute to the delay of water movement across the shell and prevents dehydration of the egg interior components.

Following the hypothesis, the study aimed to investigate eggshells' morphology and structural features derived from hens of three laying breeds and draw a line be-tween their thickness and physical-chemical properties change during 36 days of stor-age.

R: The manuscript's title doesn't clearly reflect the study's objective (L 82-84). I suggest to change the title of your study to "Impact of breed and housing condition of laying hens on quality of their eggs and eggshell thickness during storage".

A: The authors are grateful to the reviewer for the proposed excellent title of the manuscript. The authors have taken the liberty to modify it to fully reflect the study’s objective: “The impact of Eggshell Thickness on the Qualitative Characteristics of Stored Eggs Produced by Three Breeds of Laying Hens of the Cage and Cage-Free Housed Systems”

On behalf of all the co-authors

Yours sincerely,

Vitalijs Radenkovs

Principal investigator, Latvia University of Life Sciences and Technologies, Research Laboratory of Biotechnology, Division of Smart Technologies.

Reviewer 3 Report

The article is of scientific interest, modern research methods are used, the results are reliable and valuable in terms of obtaining new information. The article may be published as presented.

Author Response

Dear reviewer. The authors would like to thank you for carefully checking our manuscript and for the positive evaluation of our work.

Reviewer 4 Report

In the current manuscript "The relationship between eggshell thickness and other quality features of eggs produced by the cage and cage-free housed laying hens" the authors have investigated an important issue regarding the egg quality obtained from different housing system. The paper has been well constructed and have worldwide readers. The paper is also interesting and novel parameters have been done which have much importance compared to the already published paper on the topic.

Abstract is well designed although little longer than normal studies. In introduction, most of back ground deals with the egg equality rather than housing system which is the main factor. Therefore, more stress should be put on the housing system. The following reference should be added in this regard

Impact of varying housing systems on egg quality characteristics, fatty acid profile and cholesterol content of Rhode Island Red × Fyoumi laying hens. Tropical Animal Health and Production, 53: 456 doi:10.1007/s11250-021-02913-x In materials and methods, why the albumen pH was measured.

How the single factor anova was done? I think there are two factors housing conditions and type of birds.

In results section, discussion has also been given. This must be shift to the discussion part. Ok there is no discussion part separatly. Therefore, it should be change into results and discussion part.

The conclusion section is very lengthy. It should be just few sentences based on the main results obtained.

Author Response

R: In the current manuscript "The relationship between eggshell thickness and other quality features of eggs produced by the cage and cage-free housed laying hens" the authors have investigated an important issue regarding the egg quality obtained from different housing system. The paper has been well constructed and have worldwide readers. The paper is also interesting and novel parameters have been done which have much importance compared to the already published paper on the topic.

R: Abstract is well designed although little longer than normal studies.

A: Dear reviewer. The authors are grateful for the remark. However, the authors intended to touch on all the research findings acquired in this study. Only the essence of the research has been indicated in this section.

R: In introduction, most of back ground deals with the egg equality rather than housing system which is the main factor. Therefore, more stress should be put on the housing system. The following reference should be added in this regard

Impact of varying housing systems on egg quality characteristics, fatty acid profile and cholesterol content of Rhode Island Red × Fyoumi laying hens. Tropical Animal Health and Production, 53: 456 doi:10.1007/s11250-021-02913-x In materials and methods, why the albumen pH was measured.

A: Dear reviewer. The authors are sorry that they only partly addressed the issue of the housing system and its impact on the quality of eggs. With this regard, we notify the reviewer that the proposed reference has been ensured in the Introduction section. Meanwhile, the authors extended the discussion in this section based on the observations made by Islam et al.

R: How the single factor anova was done? I think there are two factors housing conditions and type of birds.

A: The authors are sorry for misleading the reviewer with a wrongly described data processing methodology. The authors have amended this section: Data analysis was performed using arithmetical values and standard deviations. Microsoft Excel v16 software was used. The impact of factors and their interaction, the significance effect (p-value), was examined with a two-way analysis of variance (ANOVA).

R: In results section, discussion has also been given. This must be shift to the discussion part. Ok there is no discussion part separatly. Therefore, it should be change into results and discussion part.

A: Dear reviewer. The authors are grateful for the valuable remark. We have corrected the name of this section. Now it is “Results and Discussion.”

R: The conclusion section is very lengthy. It should be just few sentences based on the main results obtained.

A: Dear reviewer. The authors agree with the reviewer's point regarding the length of this section. However, we would like to ask the reviewer to retain this section without any modifications, as only the key findings of this comprehensive research were highlighted. Thank you very much!

On behalf of all the co-authors

Yours sincerely,

Vitalijs Radenkovs

Principal investigator, Latvia University of Life Sciences and Technologies, Research Laboratory of Biotechnology, Division of Smart Technologies.