Defatted Black Soldier Fly Larvae Meal as an Alternative to Soybean Meal for Broiler Chickens

Round 1

Reviewer 1 Report

That’s a nice and well-written paper, with clear objectives, correctly prepared results, good discussion and conclusion.

The topic is interesting and the paper is worth of publication. I have a few questions for clarification, some technical comments and some suggestions.

L51: Reference 22: SBM was not replaced 100%. Inclusion level of SBM was 4% in the diet containing the highest contents of INSECT MEAL 15%. Please check.

L60: Materials and Methods:  No info is presented on screen size/grinding method of main ingredients (Cereals and insect meal) Please provide relevant information.

L67: could you comment on why after oven cooking for 20 minutes at 120°C, you needed to dry at 60°C for 40 min? was the product not dry when subjected to cooking for 20 minutes at 120°C?

Table 1: What exactly is 963 next to Heavy metals?

Table 2: SBM supplied 105g/kg CP of the total calculated CP 195 g/kg or 53.8%

Insect meal supplied 81.9 g/kg CP from the total calculated CP 195 g/kg or 42% (Thus SBM supplied 28% more CP then did the insect meal)

Any comment on why the amount of insect meal chosen did not contribute to the same percentage of crude protein in the diet as in the SBM? i.e. the content of insect meal should have been 205 g/kg to provide 105 g/kg CP.

L164: why not student t-test?

L169-172: The information is already presented in table 1, any reason for the detailed repetition?

L177: “SBM had 0.4 MJ/kg greater GE”. Is this information nutritionally important?

Discussion:

In the discussion, could you comment on the difference between the inclusion level of wheat between the diets? and whether the higher wheat content in the Insect meal-based diet may have contributed to the difference in performance particularly no NSPases (i.e. xylanase) was added in the diet.

L225-226: any comments on the texture or particle size of the Insect meal. Was there any problem with dust? Feed spillage? Feed selection? I suggest commenting briefly on these points.

L 251: this and the fact that Insect meal contributed to less CP in the diet than did SMB

L258: but this was not the case in the study (56) you have referenced, so the higher content of saturated fat in insect meal may not necessary be the cause for the reduced AMEn. Please check again.

L265: inhibited

L275: these further suggest

L282-283: pelleting was not used in the current study, so I am not sure why this is mentioned.

L302: gaining momentum? enzyme addition is generally a common and standard practice for quite some time now.

Author Response

That’s a nice and well-written paper, with clear objectives, correctly prepared results, good discussion and conclusion.

The topic is interesting and the paper is worth of publication. I have a few questions for clarification, some technical comments and some suggestions.

L51: Reference 22: SBM was not replaced 100%. Inclusion level of SBM was 4% in the diet containing the highest contents of INSECT MEAL 15%. Please check.

Response VP – Thank you for spotting this error. Reference 22 should have been in support of the line below. Now changed in text.

L60: Materials and Methods:  No info is presented on screen size/grinding method of main ingredients (Cereals and insect meal). Please provide relevant information.

Response VP – The insect meal was obtained as finely milled from the producer. Cereals were milled by hummer mill and 6 mm mesh.

L67: could you comment on why after oven cooking for 20 minutes at 120°C, you needed to dry at 60°C for 40 min? was the product not dry when subjected to cooking for 20 minutes at 120°C?

Response VP – The meal was conditioning for 40 min before fat separation. Now added detail in text.

Table 1: What exactly is 963 next to Heavy metals?

Response VP – There was an error during formatting. Now deleted. Table rechecked for accuracy.

Table 2: SBM supplied 105g/kg CP of the total calculated CP 195 g/kg or 53.8%

Insect meal supplied 81.9 g/kg CP from the total calculated CP 195 g/kg or 42% (Thus SBM supplied 28% more CP then did the insect meal).

Any comment on why the amount of insect meal chosen did not contribute to the same percentage of crude protein in the diet as in the SBM? i.e. the content of insect meal should have been 205 g/kg to provide 105 g/kg CP.

Response VP – It is known that insect meal contains non-protein nitrogen and therefore 6.25 as a conversion factor is inaccurate, therefore the concept of using crude protein may not be the best approach when formulating these diets. We have therefore chosen to balance the diets on an overall isonitrogenous basis. We have discussed the issue of CP and conversion factors later in the manuscript.

L164: why not student t-test?

Response VP – T-test would also be appropriate but give the same answer as the one-way ANOVA in this case.

L169-172: The information is already presented in table 1, any reason for the detailed repetition?

Response VP – This is drawing the reader’s attention to the findings and the information in the table. Agree, this may not be essential information, however it is desirable to improve the readability of the manuscript in our view.

L177: “SBM had 0.4 MJ/kg greater GE”. Is this information nutritionally important?

Response VP – The GE is not essential information but is helpful to diverse range of readers, who may require this information.

Discussion:

In the discussion, could you comment on the difference between the inclusion level of wheat between the diets? and whether the higher wheat content in the Insect meal-based diet may have contributed to the difference in performance particularly no NSPases (i.e. xylanase) was added in the diet.

Response VP – We have stated the fact that insect meal contains antinutritional factors and the diet formulation being different would indeed have differences (lines 243 – 247). The wheat is therefore one of these components. We have acknowledged that having two different diet formulations may complicate the findings but have tried to limit this impact and to mitigate as best we can with the formulations.

L225-226: any comments on the texture or particle size of the Insect meal. Was there any problem with dust? Feed spillage? Feed selection? I suggest commenting briefly on these points.

Response VP – The insect meal was obtained as finely milled from the producer. In theory birds may be more selective with mash diets compared to pelleted diets. However, we only have anecdotal evidence for limited selection but no measurements to quantify.

Now added in text (line 227) “Mash diets may be more susceptible to selective feeding of dietary ingredients, however this is likely to be limited in practice and no measurements are available for the present study.”

L 251: this and the fact that Insect meal contributed to less CP in the diet than did SMB

Response VP – Agree

L258: but this was not the case in the study (56) you have referenced, so the higher content of saturated fat in insect meal may not necessary be the cause for the reduced AMEn. Please check again.

Response VP – Thank you for the valuable comment. We have done further reading on this point and changed the sentence “Saturated fats are poorly digested by young birds in comparison to unsaturated [55], however, whilst insect fat contains a greater content of saturated fatty acids compared to soya oil and therefore could reduce AMEn and FD, this is not consistent with the findings of others [56].” (line 256).

L265: inhibited

Response VP – Agree, changed in manuscript.

L275: these further suggest

Response VP – Agree, changed in manuscript.

L282-283: pelleting was not used in the current study, so I am not sure why this is mentioned.

Response VP – We are discussing a general point that in commercial pelleted diets attention needs to paid to pelleting practises. We have clarified the sentence by adding additional wording to make it clear we are discussing commercial practise.

“Further damage to sensitive nutrients, e.g. vitamins and lysine, may also result from prolonged steam pelleting during subsequent diet manufacture [65], often done commercially.”

L302: gaining momentum? enzyme addition is generally a common and standard practice for quite some time now.

Response VP – We changed to better reflect our point in text:

“The use and development of various feed additives, including enzymes is a topic of ongoing research in poultry nutrition [71,72], to improve protein and carbohydrate digestibility resulting in improved growth performance [73,74], and potentially improved litter quality as a consequence of enhanced nutrient utilization.

Reviewer 2 Report

Diet formulation concerns.

The author’s goal was to evaluate the potential effects of replacing SBM with BSFL on performance. Below are the main issues with the diet formulation.

1.    High Level of Wheat in the BSFL Diet. BSF diet was formulated with a high level of wheat instead of corn. Wheat has high levels of NSPs which can pose challenges for broiler chicks in term of digestibility which can results in slower growth rate and lower feed conversion efficiency, the potential impact of NPSs should have been considered during formulation.

2.    Variability in Crude Fat Levels: There seem to be a big variability in crude fat levels between the control and insect meal how do the authors account for this variability in terms of performance….

3.    Small Number of Birds (3/Replicate):What was the main reason for use of a small number of birds (3/replicate) 

No  issues  with quality of English. 

Author Response

Diet formulation concerns.

The author’s goal was to evaluate the potential effects of replacing SBM with BSFL on performance. Below are the main issues with the diet formulation.

1. High Level of Wheat in the BSFL Diet. BSF diet was formulated with a high level of wheat instead of corn. Wheat has high levels of NSPs which can pose challenges for broiler chicks in term of digestibility which can results in slower growth rate and lower feed conversion efficiency, the potential impact of NPSs should have been considered during formulation.

Response VP – Thank you for the question. In text we have stated the fact that insect meal contains antinutritional factors and the diet formulation being different would indeed have differences (around lines 243 – 247). The wheat is therefore one of these components. We have acknowledged that having two different diet formulations may complicate the findings but have tried to limit this impact and to mitigate as best we can with the formulations.

2. Variability in Crude Fat Levels: There seem to be a big variability in crude fat levels between the control and insect meal how do the authors account for this variability in terms of performance…

Response VP - One incongruity common to these studies is that the difficulty of balancing the metabolizable energy level of the diets due to the differences in metabolizable energy content of raw materials. An inevitable solution for this dilemma is supplementation (compensation) with fat/oil, as was the case in this study. Although mathematically a solution seems to have been found, the metabolic implications of this still remain open question.

3. Small Number of Birds (3/Replicate): What was the main reason for use of a small number of birds (3/replicate)

Response VP – There was a limited amount of insect meal so we had limit on number of birds we can involve in experiment.

 Comments on the Quality of English Language - No issues  with quality of English. 

Reviewer 3 Report

Dear Authors,

The production of soybean meal has a substantial impact on the environment and reducing its inclusion in poultry diets by using alternative protein sources, such as insect meal, is an important challenge for nutritionists. The optimum amount of insect meal that can be incorporated in poultry diets to guarantee optimal animal productive performance still needs to be established.

But I have some quastions/suggestions:

·      The title does not reflect the content of the manuscript.

·      Too bad there were not more experimental groups with a different amount of meal from Black Soldier Fly Larvae.

·      How much water did the birds in both groups drink - was this studied?

·      You write about a study of litter quality and there is no data on this in the manuscript.

·      Why was there such a difference in the fat/crude fat content of the feed, and what effect could this have had on production results and meat quality?

Further research into standardising insect rendering and production methods should be prioritised by the industry. Research on the use of feed additives, alongside processing techniques and refining insect meal inclusion levels to reduce the negative impact of chitin and improve/ preserve the nutrient availability of insect meal for poultry is essential through future research.

Comments for author File: Comments.pdf

Author Response

Dear Authors,

The production of soybean meal has a substantial impact on the environment and reducing its inclusion in poultry diets by using alternative protein sources, such as insect meal, is an important challenge for nutritionists. The optimum amount of insect meal that can be incorporated in poultry diets to guarantee optimal animal productive performance still needs to be established.

But I have some quastions/suggestions:

• The title does not reflect the content of the manuscript.

Response VP – Dear Colleague, thank you for the comment. Whilst we appreciate the experimental data in the paper is not very big one, we use this to discuss much wider issues with formulating poultry diets containing insect meal. The title of the paper is designed to articulate these important points and draw attention to them. We believe this manuscript is therefore a valuable addition to the literature in this topic.

• Too bad there were not more experimental groups with a different amount of meal from Black Soldier Fly Larvae.

Response VP – We did not aim to compare the impact of graded levels of insect meal in replacement of SBM on growth performance variables of broiler chickens. This study aimed to compare the productive performance of broiler chickens fed one of two isonitrogenic and isocaloric diets. The first diet contained SBM as the main protein source, whereas SBM was completely replaced by defatted meal from Black Soldier Fly Larvae in the second diet.

• How much water did the birds in both groups drink - was this studied?

Response VP – We did not measure water intake. However, based on the findings in this study, water intake measurement may be considered in further research.

• You write about a study of litter quality and there is no data on this in the manuscript.

Response VP – We presented information on moisture of fresh excreta, daily voided wet and dry excreta on Table 4. Those are variables that can be used to characterise litter quality.

• Why was there such a difference in the fat/crude fat content of the feed, and what effect could this have had on production results and meat quality?

Response VP – Sometime is difficult to balance the metabolizable energy in diets containing raw materials with different available energy & chemical composition. An inevitable solution for this dilemma is supplementation (compensation) with fat/oil, as was the case in this study. Although mathematically a solution seems to have been found, the metabolic implications of this remain open question.

Further research into standardising insect rendering and production methods should be prioritised by the industry. Research on the use of feed additives, alongside processing techniques and refining insect meal inclusion levels to reduce the negative impact of chitin and improve/ preserve the nutrient availability of insect meal for poultry is essential through future research.

Reviewer 4 Report

This copy is not acceptable as full paper.  

I have noted some of the issues that warrant this paper not to be accepted as full paper.

Title of the study is too broad,  which is in the structure of review. one can suggest to narrow it  to accommodate trial held in the study 

This work should be considered as short communication or short note instead of a paper.

This whole manuscript is too narrow and it never addressed the depth of the title. 

"Unlocking their Full Potential" but the author only focused on growth and digestibility. The digestibility trial can also produce results from the lab, but what we are observing here are the calculated/estimated parameters mentioned. 

The authors collected digestibility data for three days, but 25-28 is four days (25 26 27 and 28).

Are these four days enough to determine the digestibility?.

These are irrelevant when running monogastric trial. The authors can put crude fibre as opposed to these ones.

Author Response

This copy is not acceptable as full paper.  

I have noted some of the issues that warrant this paper not to be accepted as full paper.

Title of the study is too broad,  which is in the structure of review. one can suggest to narrow it  to accommodate trial held in the study 

This work should be considered as short communication or short note instead of a paper.

This whole manuscript is too narrow and it never addressed the depth of the title. 

"Unlocking their Full Potential" but the author only focused on growth and digestibility. The digestibility trial can also produce results from the lab, but what we are observing here are the calculated/estimated parameters mentioned. 

Response VP – Thank you for the comment. Whilst we appreciate the experimental data in the paper is narrow, we use this to discuss much wider issues with formulating poultry diets containing insect meal. The title of the paper is designed to articulate these important points and draw attention to them. We believe this manuscript is therefore a valuable addition to the literature in this topic, as verified by the other reviewers.

The authors collected digestibility data for three days, but 25-28 is four days (25 26 27 and 28).

Are these four days enough to determine the digestibility?

Response VP – This is a standard practise in poultry research when using total collection technique.

These are irrelevant when running monogastric trial. The authors can put crude fibre as opposed to these ones.

Response VP – Thank you for your comment. In this case we are using ADF and ADL to calculate the amount of chitin making these measures completely relevant to this paper. Fibre nutrition in monogastrics is very important and has moved from crude fibre to more detailed descriptions. Depending on context measures of soluble fibres and fractionated non-starch polysaccharides are entirely appropriate in poultry nutrition, particularly in relation to fermentation and prebiotics.

I therefore recommend that this copy be rejected for publication.

The editor can choose other alternatives such considering it as short note or short communication.

Reviewer 5 Report

General comments

The authors analyzed the effects of two diets one with soybean meal and the other defatted meal from Black Soldier Fly Larvae. Ross 308 female broilers were used and from 10 to 28 days a digestibility assay was performed.

The experimental design was adequate with 2 treatments, and 12 repetitions of 3 female broilers. In the actual version, the results are clearly presented, and the discussion is relevant and complete.

The tables are clear, non-repetitive, and concise.

In general, the manuscript is well written and understandable to a specialist readership; the organization and structure of the article are good and in accordance with the journal instructions for authors. The subject is adequate for the journal's scope.

I recommend the acceptance of the paper after Minor revision, considering these comments.

General comments – check all text and change the scientific names of insects in text and references to italic.

Specific comments are described below.

Title – In my opinion, this title does not describe the study. When I read it, I expected some studies using different insect sources and the composition of them.

 Abstract

The purpose of the study is clearly defined.

Extra information about methodology and results will improve the abstract. For example, consider inserting a female broiler (Ross 308) in the animal description, the age of the animals, variables analyzed, and statistical tests.

The conclusion is not clear. It is a discussion.

Key words – adequate. 

Introduction

A huge first paragraph. There are a lot of subjects together: poultry meat production, soybeans, and insects.

There is no clear hypothesis. Please insert it before the objective.

Methodology

Line 76 – TiO2 chemical formula, subscribe 2.

Table 1 – I suggested using lysine and Methionine in digestible values.

Line 105 Correct the term – vitelline diverticulum – we do not use eponymous anymore to describe structures.

Line 106 – by pen or by cage?

Results – consider them complete in all titles tables:

Table 3: … in female broilers (10–28 d)

Table 4: … at study end point (... day)

Discussion

Lines 228-242- What was the n6:n3 relation estimated for diets in the experiment? Compare these comments.

 Line 238: However, it should be noted that in these five studies, dietary SBM was not completely substituted with BSFL, which is different from the present study.

Consider writing in a different way. The Diet with BSFL was formulated with different amounts of corn, wheat, amino acids, and BSFL in order to meet the SBM nutrients.

 References 71 to 74 are completely unnecessary.

Conclusion – only the first 3 lines are conclusions. Move sentences to the discussion. Answer the hypothesis in the conclusion.

Author Response

General comments

The authors analyzed the effects of two diets one with soybean meal and the other defatted meal from Black Soldier Fly Larvae. Ross 308 female broilers were used and from 10 to 28 days a digestibility assay was performed.

The experimental design was adequate with 2 treatments, and 12 repetitions of 3 female broilers. In the actual version, the results are clearly presented, and the discussion is relevant and complete.

The tables are clear, non-repetitive, and concise.

In general, the manuscript is well written and understandable to a specialist readership; the organization and structure of the article are good and in accordance with the journal instructions for authors. The subject is adequate for the journal's scope.

I recommend the acceptance of the paper after Minor revision, considering these comments.

General comments – check all text and change the scientific names of insects in text and references to italic.

Response VP – Now completed in text.

Specific comments are described below.

Title – In my opinion, this title does not describe the study. When I read it, I expected some studies using different insect sources and the composition of them.

Response VP – Whilst we appreciate the experimental data in the paper is not very big, we use this to discuss much wider issues with formulating poultry diets containing insect meal. The title of the paper is designed to articulate these important points and draw attention to them. We believe this manuscript is therefore a valuable addition to the literature in this topic.

Abstract

The purpose of the study is clearly defined.

Extra information about methodology and results will improve the abstract. For example, consider inserting a female broiler (Ross 308) in the animal description, the age of the animals, variables analyzed, and statistical tests.

The conclusion is not clear. It is a discussion.

Response VP – We have limited number of words to use so that’s why we cannot present all technical information.

Key words – adequate. 

Introduction

A huge first paragraph. There are a lot of subjects together: poultry meat production, soybeans, and insects.

There is no clear hypothesis. Please insert it before the objective.

Response VP – Hypothesis added in text.

Methodology

Line 76 – TiO2 chemical formula, subscribe 2.

Response VP – Done.

Table 1 – I suggested using lysine and Methionine in digestible values.

Response VP – Done.

Line 105 Correct the term – vitelline diverticulum – we do not use eponymous anymore to describe structures.

Response VP – Done.

Line 106 – by pen or by cage?

Response VP – By pen.

Results – consider them complete in all titles tables:

Table 3: … in female broilers (10–28 d)

Table 4: … at study end point (... day)

Response VP – Done.

Discussion

Lines 228-242- What was the n6:n3 relation estimated for diets in the experiment? Compare these comments.

Response VP – Now some changes were made (line 241).

Line 238: However, it should be noted that in these five studies, dietary SBM was not completely substituted with BSFL, which is different from the present study.

Consider writing in a different way. The Diet with BSFL was formulated with different amounts of corn, wheat, amino acids, and BSFL in order to meet the SBM nutrients.

Response VP – Now changed in text.

References 71 to 74 are completely unnecessary.

Response VP – We found them useful to describe/ explain better the experimental results.

Conclusion – only the first 3 lines are conclusions. Move sentences to the discussion. Answer the hypothesis in the conclusion.

Response VP – Now some changes were made.

Reviewer 6 Report

At the outset, I would like to thank you for the opportunity to participate in the review of the manuscript concerning the understanding of nutritional value of insect products in-tended for animal feed is key to unlocking their full potential.

The introduction to the article is clearly written, introduces the topic well, the selection of literature is appropriate.

The purpose and scope of the article have been correctly defined. The methodology is clearly written and makes it possible to repeat the experiments. The results and discussion are well presented.

The study examined the impact of replacing 16% of Soybean Meal (SBM) in broiler chicken diets with Black Soldier Fly Larvae (BSFL) meal. This substitution affected energy and nutrient digestibility, influencing broiler growth due to BSFL's chitin content and potential inaccuracies in digestibility assumptions. Notably, BSFL introduction reduced excreta moisture, suggesting improved litter quality. While complete SBM replacement posed challenges, partial substitution with BSFL could be more viable. However, careful consideration of factors like insect processing, additives, mineral balance, and Amino Acid supplementation is crucial. The study highlights the need for refining insect production methods and industry standards. This aligns with the pursuit of sustainable animal nutrition and emphasizes the importance of optimizing insect-based feed practices for enhanced livestock systems and feed sustainability.

I consider the entire manuscript interesting and worthy of attention. The manuscript was pleasant to read.

Overall, nice work. Congratulations.

Author Response

Comments and Suggestions for Authors

At the outset, I would like to thank you for the opportunity to participate in the review of the manuscript concerning the understanding of nutritional value of insect products in-tended for animal feed is key to unlocking their full potential.

The introduction to the article is clearly written, introduces the topic well, the selection of literature is appropriate.

The purpose and scope of the article have been correctly defined. The methodology is clearly written and makes it possible to repeat the experiments. The results and discussion are well presented.

The study examined the impact of replacing 16% of Soybean Meal (SBM) in broiler chicken diets with Black Soldier Fly Larvae (BSFL) meal. This substitution affected energy and nutrient digestibility, influencing broiler growth due to BSFL's chitin content and potential inaccuracies in digestibility assumptions. Notably, BSFL introduction reduced excreta moisture, suggesting improved litter quality. While complete SBM replacement posed challenges, partial substitution with BSFL could be more viable. However, careful consideration of factors like insect processing, additives, mineral balance, and Amino Acid supplementation is crucial. The study highlights the need for refining insect production methods and industry standards. This aligns with the pursuit of sustainable animal nutrition and emphasizes the importance of optimizing insect-based feed practices for enhanced livestock systems and feed sustainability.

I consider the entire manuscript interesting and worthy of attention. The manuscript was pleasant to read.

Overall, nice work. Congratulations.

Response VP – Thank you for the positive review.

Round 2

Reviewer 4 Report

I would like to alert you that i rejected the same manuscript previously based on the shortage of tables to strengthen then whole manuscript and title.

Author Response

Thank you for the comment. Now we have changed the title of the paper and optimised the literature used to support our manuscript. The tables with results from the animal study provide information on 18 variables including bird growth performance, energy, nutrient metabolism and litter quality. Thus, we believe this manuscript brings valuable information to the knowledge in this topic, as agreed by the other reviewers.