Different Diets Based on Yellow Mealworm (Tenebrio molitor)—Part A: Facing the Decrease in Omega−3 Fatty Acids in Fillets of Rainbow Trout (Oncorhynchus mykiss)
, Daniel Rico 1, Dmitri Fabrikov 2, Fernando G. Barroso 2, Alba Galafat 2, Francisco Javier Alarcón 2, Amalia E. Morales 3, M. Carmen Hidalgo 3, Helena M. Lourenço 4,5, María-Fernanda Pessoa 6 and Cristina Tomás-Almenar 7,*
Round 1
Reviewer 1 Report
Dear authors,
while feeding insect meals to fishes is a (potentially) new sustainable way to replace fishmeal or soybean meal (or other less sustainable protein sources), I am generally missing aspects about the sustainability.
In total, you are providing interesting data which is of interest for the sector. However, the manuscript lacks significant focus, at least in the introduction and especially in the results/discussion section.
As the current state is, I am sorry to let you know, that I would not accept the mansucript in its current state.
Many suggestions for improvement are noted in the commented version of the PDF. Additionally, you should consider to split the manuscript in two papers since it is a ton of data you generated. It is understandable, that ou want to show all the data but the reader will be overwhelmed. Furthermore, you are discussing many things (some of them in very little detail and others in way too much detail or too lengthy) but I am seriously missing discussions about sutainability (although sustainability is not your main focus but rather performance, biology, FA utilization etc., it is used in the introduction as the "main red line" and should be kept as "red line" throughout the paper). Why should I feed valuable algal omega-3 oils to raibow trout instead consuming it myself? Same with the IM. Under current EU legislation, it is only allowed to feed feed-grade material to insects. However, while IM is currently kind of hyped, the way it is produced now cannot be more sustainable than feeding the insect feed directly to other livestock (pigs, chicken). Splitting the manuscript in two, would give sufficient space to elaborate more into that direction.
The other option would be to focus on relevant data and shorten the whole manuscript considerably in order not to overload it.
Please be not offended by the comments in the mansucript, they are meant helping you to improve the manuscript, although they might sound very critical sometimes!
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Reviewer 2 Report
The present MS deals with an intersting topic related to the necessity to improve the FA quality of aquafeeds including insect meal.
Generally the MS is clear and well written. The only aspect that i do no like is to have results and discussion together, but may be this was requested by this journal.
Before its publications some revisions are requested.
Introduction
L 54 Please consider a hnumber of papers that tested conpletely FM free diets in trout, seabream and other species. This aspect should be included to link the vegetable ingredients to the new and sustainable ones.
L82-83 there are new recent studies that should be considered by the authors for the enrichment procedure , as an example state:
Black Soldier Fly (Hermetia illucens) reared on roasted coffee by-product and Schizochytrium sp. as a sustainable terrestrial ingredient for aquafeeds production
Zarantoniello et al. ,
l 88 a reference is necessary, and the following review is a recent overview about the use of laboratory methods imporrtant for studying IM diets in fish
Application of laboratory methods for understanding fish responses to black soldier fly (Hermetia illucens) based diets
Zarantoniello, M., et al ,Author Response
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Reviewer 3 Report
Overall comments
The omega-3 level in T and dT diets were different. Therefore, it is questionable whether the increase in muscle omega-3 level was attributed to high fish oil level or reduced insect fat in dT diet. The result of this study would be more valuable if the T diet contained similar fish oil level to dT diet.
There are numbers of published articles about fish meal replacement with TM and defatted insect meal in diets for rainbow trout. Authors better use findings of those articles to discuss the result of this study. The information is also important to justify the objectives of the study.
Please check all the abbreviations. Several terms are abbreviated repeatedly (ex: EPA, DHA). The abbreviation style is also confusing. The second diet is represented by one letter (“T”). It is better to change T to TM50 and dT to dTM.
Abstract
The abstract does not give a comprehensive idea regarding the experiment conducted.
Treatment groups of the experiment are not described well, and it is very confusing to understand the main objective of the experiment undertaken.
Line 30: What is the experimental algal oil used in the current study?
Line 33-34: The logic about the omega-3 sparing effect is questionable, because the diets contained different omega-3 levels.
Introduction
The introduction section does not give an overview on the yellow mealworm, or the additive (algal oil?) nor the specific importance. There are many published articles related to defatted insect meal and yellow mealworm in diet for rainbow trout. Please mention them briefly and compare them before your objectives.
The specific reasons to select the algal oil source is not explained well (algae species, fatty acid composition)
Even though, authors claim that algal oil is rich in omega 3 fatty acids, there is no scientific evidence presented to confirm their claims.
Authors should explain more on the benefits of using defatted insect meal (IM) over full fat IM.
Line 69: FA → fatty acid
Materials and method
The method of algal oil extraction is not described.
Line 101-108: No need to abbreviate IM, EPA, DHA again in Material and method section. Because these are already mentioned in the introduction.
Line 104-106: Remove manufacturer’s details of TM meal to increase the readability. Because it is already mentioned in the description of Table 2 a.
Line 107: Does EO mean algal oil or omega-3 enriched oil? We suggest authors to present fatty acid level of algal oil.
Line 135: Is there any special reason to use female fish?
Line 142-143: Why were the fish fed only once a day (9am)? For optimal growth, it would be appropriate to feed the fish at least twice a day. It's likely that a significant amount of feed was lost.
Line 155-159: This is not clear. How many fish were used for sensorial analysis, enzyme determination and histomorphology analysis? Which samples/organs were used for enzyme determination and histomorphology analysis?
Line 165: When fillets are frozen, they lose texture and elasticity due to tissue breakdown. Why did you use freeze fillets for your analysis? Please provide references to the corresponding analytical methods.
Results and discussion
The effects and the suitability of the algal oil as a feed additive in the diets of rainbow trout is poorly described and discussed.
Why is the content of ∑Omega-3 (n-3) higher in the defatted insect meal group than in the full-fat insect meal group? Supplement the analysis of fatty acids composition of fish meal LT94, T. molitor and defatted T. molitor.
Supplement the discussion of 3.2.2. fillet perceived quality. Not convincing.
Line 285-290: There are number of studies conducted on the fish meal replacement with IM in rainbow trout diet. Authors should follow their findings to construct a logical explanation in this part.
Line 317-320: Does that mean that rainbow trout use insect fats instead of omega-3?
Line 323-325: It is not about the content of fat, usually specific fatty acids that are higher in diets accumulate in liver and muscles reflecting the dietary composition. For example, in your diet formulation, the pattern of fatty acids composition in diet approximately reflecting fatty acid composition in fillet.
Line 355-362: Fillet fatty acid levels are still representing the diet fatty acid composition.
Line 377-392: Authors need to provide possible explanations for changes of muscle color?
Line 422-433: There is a lack of discussion that the addition of yellow mealworm reduced antioxidant activity. Please explain additionally.
Line 430-433: As you claim, the MDA accumulation and decreased GPx activity seen in this study may not have caused a problem over the 89-day experimental period. However, this decrement in antioxidant capacity may lead to a decrease in resistance to stress and infectious diseases in the long term, and thus this finding requires your further consideration.
Conclusions
I think that just the reduction of insect fat and increase of fish oil was the reason for increase in omega-3 level in fillet of fish fed dT diet. According to another parameters, there are no considerable advantages of the dT diet compared to T.
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Round 2
Reviewer 1 Report
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Comments for author File: Comments.pdf
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Reviewer 2 Report
Thank you very much for revising your MS in a correct way
Author Response
Due to the fact that Reviewer 2 did not add any more recommendations or corrections for this new round of revisions, all we can do is to greatly appreciate their contributions.
Reviewer 3 Report
Authors have improved manuscript with reviewers’ comments.
Line 107-108: It is better to abbreviate EO here except line 129 in Materials and Method.
Line 174-180: The information in the brackets is disturbing for the readability. Therefore, it is better to mention that information incorporates with sentence without using brackets.
Line 498-501: Please provide some references for sustainable healthy limit?
I suggest authors to mention about Schizochytrium sp oil in conclusion.
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