Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

REVIEW OF animals-4140450

The authors review some of the more important drought-tolerant agricultural crops as potential livestock feeds, examining the major variables that determine crop yield, plant composition, and animal digestibility. Overall, the review is impressively comprehensive, and generally well-written. Some suggestions are provided below, aimed at improving clarity and readability. (Note: Given the length of the manuscript, please highlight all changes in any manuscript revision).

Specific comments:

L27: The term “crucial” is used here and frequently throughout the manuscript, but the reviewer believes that its use is improper. “Crucial” implies a sort of essentiality or necessity, that does not fit most of the cases to which the authors apply it. Perhaps use an alternative adjective such as “important”.

L68-70: Here and throughout the manuscript, he authors use the terms “drought resistant” and “drought resilient” without definition, and they also seem to use the term interchangeably. If the two terms are indeed interchangeable, then the authors should select one term and stick with it. If the terms are not intended to be interchangeable, please provide an explicit definition for each term.

Fig.1: Although it would not change the data, the graphs would be more dramatic if the y-axis was flipped, with 0 at the top, and the bars pointing downward rather than upward.

L147-160: The authors here describe three of the factors of drought resilience, but do not describe the fourth (drought recovery, L141).

L174-176: Isn’t this sentence true for all plants, not just drought-resilient ones?

L237-238: It would be useful here to indicate the range of DMs of the two different groups of plants.

Figure 3: What do the blue irregular blobs at the bottom center of the figure represent?

L261: Do the authors mean here true protein, or crude protein (N x 6.25)?

L322-324: Based on what is known in other BMR forages, it seems like the enhanced digestibility is due not to a higher fiber content per se, but rather to a decreased level of lignin, or decreased lignin-carbohydrate bonding in the BMR varieties.

L337-339: In this latter study in sheep, “negatively impacted” relative to what? Also rice straw, or something else? With regard to rice straw, one factor contributing to its poor digestibility is its very high content of ash, sometimes approaching 20% of DM. Could some of the benefit for millet merely be due to its lower ash content?

L354-359: Are these the proper units (% grams per day)? Do the authors just mean g/d?

L360: Why is a high water content beneficial for a feed? More water equals more effort to haul and store the biomass without improving its nutrient value.

L360: Elevated compared to what?

L366: Do the authors mean replacement of 30% of the maize with an equivalent amount of the false banana? And are these replacements on a DM basis?

L372: Not clear what the authors mean by “in vitro organic DM”? Do the authors mean increased in vitro DM digestibility (or OM digestibility)?

L386: Still, this is less than 1 g per kg.

L397: By “impacted”, do the authors mean “improved”?

L435: What is meant by “ruminating efficiency”. Is it time spent ruminating per day, or what?

L446: Do the authors mean relative to alfalfa (rather than “better than alfalfa”)?

Table 1: This is an impressively comprehensive table, but it is a little hard to read. Suggest pasting the information into a template that separates the information in rows and columns demarcated by solid lines, for easier reading.

L469-473: These two sentences say basically the same thing. Please rewrite as one single sentence.

L481-483: This sentence needs to be rephrased, as the statement is not at all true regarding forage crops generally, though it may be true for drought-tolerant crops.

L489 Performed better in what regard? Yield? Nutrient composition? Digestibility?

L518-522: The authors should explain whether, and why, increased pectin content improves forage quality.

L586-590: These statements imply a tight connection between yield and quality, but isn’t it true that plants harvested at highest yield (greater maturity) tend to have reduced quality due a greater extent of lignification? (The authors allude to this in L604-609 and L648-652).

L729-731: This is an intriguing observation, but a mechanistic explanation is needed. Do different drying techniques perhaps drive off different amounts of volatile materials, thus increasing fiber content? Or do different drying methods cause different extent of chemical reactions among the remaining fiber components, such that they respond differently to subsequent fiber analytical methods?

L773-775: By itself, it’s hard to conclude much from the stated zone of inhibition without considering the assay conditions (e.g. amount of extract used), or how the value compared to a control. Perhaps just state that there was a substantial level of inhibition.

L794-826: This entire section only discusses the beneficial effects of feed grinding on the performance of nonruminant animals. The situation for ruminants is more complex, because the benefits of grinding (increased surface area for ruminal degradation) are counterbalanced by faster rates of passage of the feed before it can be productively fermented to VFA in the rumen. Has grinding of drought-tolerant crops been evaluated in a ruminant context?

L828-834: Ensiling is also of potential importance in regions experiencing rapid weather changes such as episodic severe precipitation events, as these heavy rains can ruin crops set out for conventional drying. Ensiling can be used to rescue such harvests that would otherwise be destroyed.

L922, L931: Aflatoxins do not “grow”. Do the authors mean production rather than “growth”.

L971; This statement seems odd. Aren’t droughts typically associated with low humidity?

L1008: The mycotoxins compromise feed safety, not “feed safety standards”.

L1028-1031: It is true protein, not crude protein, that is crucial for living organisms. CP is merely a means of estimating true protein. So perhaps change “it” (CP) in L1028 to “protein”.

L1119-1120: This is gross energy, not metabolizable energy.

L1127-1130: The authors really need to point out here that these conclusions are based on correlations. There is no evidence that any of the listed species can degrade lignin.

L1138-1148: The authors need to point out here that these pretreatments have numerous disadvantages that have limited their use including 1) cost; 2) logistic and safety issues when working with toxic chemicals; and 3) preventing spoilage of the now-more digestible feedstuffs prior to feeding.

L1193-1252: These two sections emphasize the issues confronting small-scale farmers regarding the application of drought-resilient crops. It seems that some (perhaps most) of these issues would also challenge large-scale farmers as well, particularly in developing countries. This should be noted.

L1268-1283: The researchers here lay a lot of blame on academic institutions, but shouldn’t some of the necessary research be supported by the private sector, particularly those companies that produce seeds and other products for drought-resilient agriculture? Why aren’ t these private companies stepping up to recruit small-scale farmers for on-the-ground research? Successful demonstration projects on the local level would seem an ideal way to get the varieties and technologies in front of the small-scale farming community as quickly as possible.

L1340: The authors conclude their review with the statement, “Bulleted lists look like this:”, but there are no bulleted lists that follow.

Minor edits:

L26: Change “to” to “under”.

L47: Delete “parameters”.

L54: Change “inflations” to “inflation”.

L72: Change “feed alternative” to “alternative feed”.

L94: Change “is” to “are”.

L120: Delete “Evidence from”.

L122: Delete “the”.

L189: Delete “strength”.

L225: Combine “oxalo” and “acetic” to one word.

L254: Here and in the other section titles, do not capitalize species names.

L260: Change “its’” to “its” (delete apostrophe).

L260: Change “tolerant strength” to “tolerance”.

L381: Perhaps “motivation” rather than “cause”?

L506-508: Once the genus name has been provided, Opuntia can be abbreviated (O.) in subsequent usage.

L509: Italicize genus and species name (also L534, L540, L660, L720).

L525: Again, the genus name can be abbreviated.

L580: Change “general” to “conventional”.

L633: Change “prickle” to “prickly”.

L929: Change “cause” to “allow”.

L949: Change “fibrous” to “fiber”.

L1015: Change “silage” to “ensiling”.

 

 

 

Comments on the Quality of English Language

The manuscript is generally well-written, but some minor editorial suggestions are listed in the "Minor edits" in the Comments to Authors

Author Response

Reviewer #1:

 

The authors review some of the more important drought-tolerant agricultural crops as potential

livestock feeds, examining the major variables that determine crop yield, plant composition, and

animal digestibility. Overall, the review is impressively comprehensive, and generally well-

written. Some suggestions are provided below, aimed at improving clarity and readability.

Response: We thank the reviewer for their time and constructive comments, which have significantly improved the quality of our manuscript. We are pleased that the reviewer found our work comprehensive and well-written; this feedback has further motivated us to refine the paper. We have thoroughly addressed all suggestions to enhance clarity and readability. We believe the manuscript is now substantially improved and hope the reviewer and editor will find it ready for publication.

 

Comment 1: L27: The term “crucial” is used here and frequently throughout the manuscript, but the reviewer believes that its use is improper. “Crucial” implies a sort of essentiality or necessity, that does not fit most of the cases to which the authors apply it. Perhaps use an alternative adjective such as “important”.

Response: The term 'crucial' has been replaced with more accurate alternatives where its definition did not align with the intended message. Consequently, its frequency has decreased from 14 instances to approximately 6. Changes can be tracked on L45, L235, L241, L721, L839, L1212-1213.

 

Comment 2: L68-70: Here and throughout the manuscript, the authors use the terms “drought resistant” and “drought resilient” without definition, and they also seem to use the term interchangeably. If the two terms are indeed interchangeable, then the authors should select one term and stick with it. If the terms are not intended to be interchangeable, please provide an explicit definition for each term.

Response: We appreciate the insightful comment from the reviewer. "Drought resilience" and "drought resistance" are two distinct terms that are commonly used to describe the behavior of plants that grow in arid and semi-arid regions. By definition, drought resistant refers to the capacity of the plant or crop to withstand and maintain its function during water stress or deficit, while drought resilience, which is a broader term, describes the crop's overall ability to recover from the harsh conditions due to water deficit. So, the two terms, though similar, cannot be used interchangeably. However, the focus of our review is on drought-tolerant crops, as explained in the title, introduction, and section 3.1 of the manuscript. So, the review will focus on drought resilience and drought tolerance because drought-tolerant crops are often considered more aligned with resilience. Drought resistance has been removed, and the remaining terms have been used consistently in their proper context. We have clarified this in Line 83-87.

 

Comment 3: Fig.1: Although it would not change the data, the graphs would be more dramatic if the y-axis was flipped, with 0 at the top, and the bars pointing downward rather than upward.

Response: The suggestion is acknowledged, but the authors have decided to retain the current figure presentation. The axis label 'production decline' clearly communicates the reduction in maize output during El Niño-induced droughts, ensuring the visual representation remains unambiguous and scientifically accurate. The figure can be found in page 4.

 

Comment 4: L147-160: The authors here describe three of the factors of drought resilience, but do not describe the fourth (drought recovery, L141).

Response: Thank you for highlighting this important oversight; information regarding drought recovery has been added in L195-199.

 

Comment 5: L174-176: Isn’t this sentence true for all plants, not just drought-resilient ones?

Response: Thank you for your insightful comment. We have revised the statement to more precisely reflect the unique carbon-fixation capabilities of these drought-tolerant plants in L211-215.

 

Comment 6: L237-238: It would be useful here to indicate the range of DMs of the two different groups of plants.

Response: Thank you for bringing this to our attention. The sentence has been revised in order to bring empirical evidence from studies that confirm how the DM of CAM plant is 6 times greater than that of C₃ and C₄ using transpiration use efficiency as a tool. You can track the changes made from L268 -271.

 

Comment 7: Figure 3: What do the blue irregular blobs at the bottom center of the figure represent?

Response: Thank you for comment. We have addressed the comment by labelling the blue irregular blobs which are vacuoles” (Figure 3).

 

Comment 8: L261: Do the authors mean here true protein, or crude protein (N x 6.25)?

Response: Thank you for the valuable comment; we have addressed the comment by revising the statement to reflect crude protein as intended in L312.

 

Comment 9: L322-324: Based on what is known in other BMR forages, it seems like the enhanced digestibility is due not to a higher fiber content per se, but rather to a decreased level of lignin, or decreased lignin-carbohydrate bonding in the BMR varieties.

Response: While the in vitro NDF digestibility reflects overall microbial degradation of the cell wall, it does not identify which specific fiber components were degraded. Without complementary ADL and ADF analyses to distinguish between reduced lignin content and increased degradation of cellulose or hemicellulose, inferences regarding improved digestibility are limited only to overall fiber breakdown, rather than specific, verified lignin degradation This NDF digestibility of BMR can be traced in L372-376.

 

Comment 10: L337-339: In this latter study in sheep, “negatively impacted” relative to what? Also rice straw, or something else? With regard to rice straw, one factor contributing to its poor digestibility is its very high content of ash, sometimes approaching 20% of DM. Could some of the benefit for millet merely be due to its lower ash content?

Response: Thank you for the comment. The revised sentence now reads: However, a similar study found that incremental replacements of corn with finger millet above 50% in sheep diets decreased the digestibility of DM, organic matter (OM), total digestible nutrients and total carbohydrates relative to using finger millet at a concentration below 50% (L390-392).

 

Comment 11: L354-359: Are these the proper units (% grams per day)? Do the authors just mean g/d?

Response: Thank you for raising this issue. We confirm that the units are g/d without % and the revision has been affected (L399).

 

Comment 12: L360: Why is a high water content beneficial for a feed? More water equals more effort to haul and store the biomass without improving its nutrient value.

Response: In this context, high water content is a vital attribute that helps animals maintain hydration when external water sources are scarce. By consuming succulent plants like cacti, animals can access stored internal moisture, which is essential for survival in arid environments. Furthermore, offering these plants on a "fresh matter" basis can enhance overall feed intake and palatability, encouraging animals to consume other necessary nutrients (L413).   

 

Comment 13: L360: Elevated compared to what?

Response: The word elevated has been replaced with “considerable concentrations” in L414 to improve clarity.

 

Comment 14: L366: Do the authors mean replacement of 30% of the maize with an equivalent amount of the false banana? And are these replacements on a DM basis?

Response: Thank you for the insightful comment. The authors indicated that 30% of maize was substituted with 30% of false banana by weight on a dry matter basis. However, we revised the sentence on L420 to improve clarity.

 

Comment 15: L372: Not clear what the authors mean by “in vitro organic DM”? Do the authors mean increased in vitro DM digestibility (or OM digestibility)?

Response: Thank you for the comment. The term has been corrected to in vitro Organic Matter Degradability (IVOMD), as outlined by the cited author in L426-427.

 

Comment 16: L386: Still, this is less than 1 g per kg.

Response: The sentence has been edited to remove the word “significant” without losing the meaning of increased protein content in L441.

 

Comment 17: L397: By “impacted”, do the authors mean “improved”?

Response: The term “impacted” has been replaced with “improved” for clarity in L451.

 

Comment 18: L435: What is meant by “ruminating efficiency”. Is it time spent ruminating per day, or what?

Response: Thank you for the comment. We have added units according to the cited study to improve clarity. In addition, the term “ruminating efficiency” has been revised to “ruminating efficiency rate” and units have been added in L489.

 

Comment 19: L446: Do the authors mean relative to alfalfa (rather than “better than alfalfa”)?

Response: The authors mean better implying a superior performance of cactus compared to alfalfa when measuring methane production in L499-501.

 

Comment 20: Table 1: This is an impressively comprehensive table, but it is a little hard to read. Suggest pasting the information into a template that separates the information in rows and columns demarcated by solid lines, for easier reading.

Response: Comment has been accepted. The authors have added row lines to the table to improve readability. The table now is table 2 as an additional table has been included.  

 

Comment 21: L469-473: These two sentences say basically the same thing. Please rewrite as one single sentence.

Response: Thank you for the comment. As suggested, the sentences from to make one line as written in L504-506.

 

Comment 22: L481-483: This sentence needs to be rephrased, as the statement is not at all true regarding forage crops generally, though it may be true for drought-tolerant crops.

Response: Thank you for the comment. The sentence has readily been written with an emphasis and focus on drought tolerant crops in L634-635.  

 

Comment 23: L489 Performed better in what regard? Yield? Nutrient composition? Digestibility?

Response: Thank you for the comment. We have addressed the comment by adding the reported measured traits to improve the comparison (L652-654).

 

Comment 24: L518-522: The authors should explain whether, and why, increased pectin content improves forage quality.

Response: Thank you for the comment. We have addressed this by describing the benefits of increased pectin for animal nutrition, which clarifies the context of the statement in L684-688.

 

Comment 25: L586-590: These statements imply a tight connection between yield and quality, but isn’t it true that plants harvested at highest yield (greater maturity) tend to have reduced quality due a greater extent of lignification? (The authors allude to this in L604-609 and L648-652).

Response: Thank you for your insightful comment. The observation regarding reduced quality linked to lignification specifically applies to cladodes of Opuntia ficus indica and should not be generalized to all plants. We agree that asserting a universal decline in plant quality with maturity is misleading. Mature cladodes of O. ficus indica do exhibit increased lignification, which affects texture and digestibility, but this trend may not hold across other species or plant parts, these views can be found from L804-811.

 

Comment 26: L729-731: This is an intriguing observation, but a mechanistic explanation is needed. Do different drying techniques perhaps drive off different amounts of volatile materials, thus increasing fiber content? Or do different drying methods cause different extent of chemical reactions among the remaining fiber components, such that they respond differently to subsequent fiber analytical methods?

Response: Interesting comment and a thought-provoking question. The relationship between drying methods, volatiles, and fiber remains unclear, as the presence of volatiles within plant matrices is complex and influenced by factors beyond fiber content alone. This statement has been added in the manuscript to provoke further studies that could elucidate this question, in L884-890.

 

 

Comment 27: L773-775: By itself, it’s hard to conclude much from the stated zone of inhibition without considering the assay conditions (e.g. amount of extract used), or how the value compared to a control. Perhaps just state that there was a substantial level of inhibition.

Response: Thank you for bringing that of our attention. The level of inhibition has been changed to substantial in L935.

 

Comment 28: L794-826: This entire section only discusses the beneficial effects of feed grinding on the performance of nonruminant animals. The situation for ruminants is more complex, because the benefits of grinding (increased surface area for ruminal degradation) are counterbalanced by faster rates of passage of the feed before it can be productively fermented to VFA in the rumen. Has grinding of drought-tolerant crops been evaluated in a ruminant context?

Response: We appreciate your insightful comment. Research in this specific area remains sparse, with a notable lack of literature examining the effects of grinding on drought-tolerant feeds within ruminant biological systems. Consequently, we have emphasized this as a critical research gap in the manuscript (L1003-1005).

 

Comment 29: L828-834: Ensiling is also of potential importance in regions experiencing rapid weather changes such as episodic severe precipitation events, as these heavy rains can ruin crops set out for conventional drying. Ensiling can be used to rescue such harvests that would otherwise be destroyed.

Response: Comment noted. We have revised the statement to add that ensiling is not only important for drought mitigation but also for regions facing erratic weather and heavy, episodic rainfall that can ruin crops intended for conventional drying (L1007-1010).

 

Comment 30: L922, L931: Aflatoxins do not “grow”. Do the authors mean production rather than “growth”.

Response: The sentence has been revised to include the word “occurrence and occur” in L1107, L1116, L1174 and L1211.

 

Comment 31: L971; This statement seems odd. Aren’t droughts typically associated with low humidity?

Response: Thank you for the comment. The term “humidity” has been removed and only the phrase “high temperature” has been kept to avoid ambiguity in L1156.

 

Comment 32: L1008: The mycotoxins compromise feed safety, not “feed safety standards”.

Response: The term “standards” has been removed and “feed safety” has been kept, as suggested in L1193.

 

Comment 33: L1028-1031: It is true protein, not crude protein, that is crucial for living organisms. CP is merely a means of estimating true protein. So perhaps change “it” (CP) in L1028 to “protein”.

Response: Comment accepted. CP has been changed to protein and emphasis has been put to highlight that “CP” is used as a measure of total protein. Subsequent sentence kept “CP” to explain its importance in feed evaluation as indicated in L1210-1217.

 

Comment 34: L1119-1120: This is gross energy, not metabolizable energy.

Response: Thank you for the comment. The authors did not find the “term” metabolizable energy” within the specified lines, we would appreciate it if the reviewer can be more specific and provide the exact lines where the comment is related to.

 

Comment 35: L1127-1130: The authors really need to point out here that these conclusions are based on correlations. There is no evidence that any of the listed species can degrade lignin.

Response: The authors have pointed out that the listed species are not a direct cause of ADL degradation, it is a possibility based on other studies (L1312-1315).

 

Comment 36: L1138-1148: The authors need to point out here that these pretreatments have numerous disadvantages that have limited their use including 1) cost; 2) logistic and safety issues when working with toxic chemicals; and 3) preventing spoilage of the now-more digestible feedstuffs prior to feeding.

Response: Thank you for the comment. We have highlighted the limitations of all the highlighted treatments based on the literature, which explains their limited use, as highlighted in L1333-1341.

 

Comment 37: L1193-1252: These two sections emphasize the issues confronting small-scale farmers regarding the application of drought-resilient crops. It seems that some (perhaps most) of these issues would also challenge large-scale farmers as well, particularly in developing countries. This should be noted.

Response: Comments and suggestions are accepted and have been incorporated (L1417-1420).

 

Comment 38: L1268-1283: The researchers here lay a lot of blame on academic institutions, but shouldn’t some of the necessary research be supported by the private sector, particularly those companies that produce seeds and other products for drought-resilient agriculture? Why aren’ t these private companies stepping up to recruit small-scale farmers for on-the-ground research? Successful demonstration projects on the local level would seem an ideal way to get the varieties and technologies in front of the small-scale farming community as quickly as possible.

Response: The suggestion has been accepted and included as advised, refer to lines L1494-1501.

 

Comment 39: L1340: The authors conclude their review with the statement, “Bulleted lists look like this:”, but there are no bulleted lists that follow.

Response: The phrase has been removed as it was a typing error.

 

Minor edits:

Comment 40: L26: Change “to” to “under”.

Response: Change has been effected as suggested in L43.

 

Comment 41: L47: Delete “parameters”.

Response: “Parameters” deleted (L64).

 

Comment 42: L54: Change “inflations” to “inflation”.

Response: Change effected-L71.

 

Comment 43: L72: Change “feed alternative” to “alternative feed”.

Response: Change has been effected-L97-98.

 

Comment 44: L94: Change “is” to “are”.

Response: “is” changed to “are” in L120.

 

Comment 45: L120: Delete “Evidence from”.

Response: Phrase removed from L142.

 

Comment 46: L122: Delete “the”.

Response: Article deleted in L149.

 

Comment 47: L189: Delete “strength”.

Response: “Strength” has been removed-L219.

 

Comment 48: L225: Combine “oxalo” and “acetic” to one word.

Response: Combination has been effected. The name has been fixed and transferred into figure 2 labelling.

 

Comment 49: L254: Here and in the other section titles, do not capitalize species names.

Response: The headings have been corrected for 4.1-4.6

 

Comment 50: L260: Change “its’” to “its” (delete apostrophe).

Response: Grammar corrected in L311.

 

Comment 51: L260: Change “tolerant strength” to “tolerance”.

Response: The phrase has been changed as suggested in L311.

 

Comment 52: L381: Perhaps “motivation” rather than “cause”?

Response: “Cause” has been changed to “motivation” in L435.

 

Comment 53: L506-508: Once the genus name has been provided, Opuntia can be abbreviated (O.) in subsequent usage.

Response: Following Opuntia genus name has been changed to O were Opuntia species was written again.

 

Comment 54: L509: Italicize genus and species name (also L534, L540, L660, L720).

Response: Species and genus names have been written in a correct scientific format.

 

Comment 55: L525: Again, the genus name can be abbreviated.

Response: Comment noted and change has been implemented.

 

Comment 56: L580: Change “general” to “conventional”.

Response: Change has been done as requested in L742.

 

Comment 57: L633: Change “prickle” to “prickly”.

Response: Change has been done as requested in L793.

 

Comment 58: L929: Change “cause” to “allow”.

Response: Change has been done as requested in L1065

 

Comment 59: L949: Change “fibrous” to “fiber”.

Response: Change has been done as requested in L1134.

 

Comment 60: L1015: Change “silage” to “ensiling”.

Response: Change has been effected as requested in L1200.

Reviewer 2 Report

Comments and Suggestions for Authors

The topic of this manuscript “Advancements in Sustainable Livestock Feed: Harnessing Drought Tolerant Crops” is among the most important research and application areas in livestock. In light of climate change and increasing water scarcity, the manuscript offers new perspectives on alternative animal feed resources.

I have the following comments to help improve the manuscript:

Overall presentation is acceptable. However, it is recommended to add a subsection titled “other drought tolerant crops” and discuss additional crops that are produced and used in other countries.

It is recommended to present the chemical composition of the feed materials mentioned in the manuscript in a table, expressed as a percentage of DM, and to compare them with the main conventional feed ingredients (corn and soybean meal).

The results of the experiments should be classified by animal type (poultry, cattle, and small ruminants). This classification is necessary both in the text and in the table 1 to improve clarity and comparability.

Table 1 is not well designed and needs further summarization. The content should be organized by poultry, cattle, and small ruminants. The experimental model should be summarized, and abbreviations should be used for parameters measured and key findings to enhance readability.

Section 7 “Key Strategies for Sustainable Innovation” requires further strengthening. For example: compare relevant policies across countries.

Discuss whether governments subsidize producers or consumers to promote the development and adoption of these products.
Address why the use of drought-tolerant crops has not expanded in industrial farms (poultry, dairy).

Explore potential reasons why industrial farm, farmers remain reluctant to adopt these crops. Although they may not openly oppose them, adoption appears limited, and many producers still prefer conventional feed materials such as corn, soybean meal, alfalfa, and forage corn.

Author Response

Reviewer 2

Comment 1: The topic of this manuscript “Advancements in Sustainable Livestock Feed: Harnessing Drought Tolerant Crops” is among the most important research and application areas in livestock. In light of climate change and increasing water scarcity, the manuscript offers new perspectives on alternative animal feed resources.

Response: Thank you for the time and effort you dedicated to reviewing our manuscript; we truly appreciate your valuable feedback. We are also pleased that you recognized our research topic as a critical area in livestock science and noted its contribution of new perspectives on alternative feed resources. We have thoroughly addressed all comments in the revised manuscript and hope these revisions meet your satisfaction.

Comment 2 Overall presentation is acceptable. However, it is recommended to add a subsection titled “other drought tolerant crops” and discuss additional crops that are produced and used in other countries.

Response: Thank you for the feedback. We have added a section on 'Other Drought-Tolerant Crops' that evaluates their potential as animal feed, which we believe significantly strengthens the review, these changes can be found in L531-592.

Comment 3: It is recommended to present the chemical composition of the feed materials mentioned in the manuscript in a table, expressed as a percentage of DM, and to compare them with the main conventional feed ingredients (corn and soybean meal).

Response: Thank you for this insightful comment. We agree that this was an oversight on our part. To address this, we have added a new table (Table 1) presenting the nutritional composition of the selected drought-resilient crops compared to conventional animal feed crops. Additionally, we have included a discussion on the variations in their nutritional profiles and highlighted the significance of using mixed feed formulations to enhance overall nutritional quality. We believe this has strengthened our manuscript and better supports the subsequent recommendations for hybrid feed formulations.

Comment 4: The results of the experiments should be classified by animal type (poultry, cattle, and small ruminants). This classification is necessary both in the text and in the table 1 to improve clarity and comparability.

Response: As suggested, the animal type has been included in the updated table (now Table 2) following the addition of a new table.

Comment 5: Table 1 is not well designed and needs further summarization. The content should be organized by poultry, cattle, and small ruminants. The experimental model should be summarized, and abbreviations should be used for parameters measured and key findings to enhance readability.

Response: Thank you for the valuable comment. While organizing the content by animal type is a valid suggestion, the focus of this review is on drought-resilient crops and their processing innovations, consistent with the scope of our PhD student’s work. Therefore, we have retained the original structure, as it best supports the overall research focus and believe the current structure remains valid and does not compromise understanding of the manuscript by readers. However, to improve clarity, we have added a column to Table 2 that specifies the type of animal, as suggested.

Comment 6: Section 7 “Key Strategies for Sustainable Innovation” requires further strengthening. For example: compare relevant policies across countries.

Response: Thank you. Compelling policy intervention case studies have been added L14324-1440 and L1476 -1479.

Comment 7: Discuss whether governments subsidize producers or consumers to promote the development and adoption of these products.

Response: Thank you. The suggested comment has been addressed in a previous response.

Comment 8: Address why the use of drought-tolerant crops has not expanded in industrial farms (poultry, dairy).

Response: The suggestion has been effected in L1384-1390.

Comment 9: Explore potential reasons why industrial farm, farmers remain reluctant to adopt these crops. Although they may not openly oppose them, adoption appears limited, and many producers still prefer conventional feed materials such as corn, soybean meal, alfalfa, and forage corn.

Response: Thank you for your comment. We have strengthened the discussion section by highlighting why farmers, particularly those in the commercial sector; are often reluctant to adopt drought-tolerant crops." The changes as suggested can also be seen in L1384-1390.

Reviewer 3 Report

Comments and Suggestions for Authors

This review features a significant research topic, rigorous structure, and substantial data support. It holds important reference value for the application of drought-tolerant crops in livestock feed and aligns with the publication orientation of the Animals journal. It is recommended for publication after the authors optimize the depth of content, supplement cutting-edge research directions, and add regional adaptability analysis.

 

1. Optimization of Content Depth and Details

 

• Supplement regional adaptability analysis: Existing research cases cover regions such as Africa, the Americas, and Asia, but fail to clarify the preferred varieties and application differences of drought-tolerant crops across different climate zones (e.g., tropical arid zones vs. temperate arid zones) and farming models (large-scale intensive farming vs. smallholder subsistence farming). It is suggested to add region-specific discussions.
• Refine processing parameters: The manuscript mentions processing methods such as drying, ensiling, and grinding, but lacks integrated quantitative analysis of optimal parameters for key processes (e.g., suitable ensiling duration, optimal drying temperatures for different crops, and standard grinding particle sizes). It is recommended to supplement quantitative analysis of process-effect relationships.
• Strengthen research on synergistic application of multiple crops: Current research focuses primarily on single-crop utilization, with insufficient exploration of nutritional complementarity, palatability changes, and other effects of mixed feeding of multiple drought-tolerant crops (e.g., sorghum combined with cactus). It is suggested to add relevant discussions.

 

2. Expansion of Research Gaps and Cutting-Edge Directions

 

• Supplement prospects of emerging technologies: Existing content focuses on traditional planting and processing technologies, with no coverage of the application prospects of cutting-edge technologies such as gene editing (e.g., developing high-protein drought-tolerant varieties) and microbial fermentation (e.g., compound probiotics to enhance nutrient conversion). It is recommended to add research prospects for these directions.
• Improve environmental and economic assessments: The manuscript lacks systematic analysis of the carbon footprint, water consumption, and cost-effectiveness of drought-tolerant crop cultivation and feed production. It is suggested to supplement life cycle assessment or comparative economic benefit data to strengthen the sustainability argument.
• Expand research on underutilized crops: For less-studied crops such as false banana (Ensete ventricosum), existing data are limited to specific regions (e.g., Ethiopia). It is recommended to supplement data on planting adaptability and feeding effects from more regions to enrich the range of crop options.

 

3. Optimization of Expression and Structure

 

• Standardize professional terminology: Some terms have inconsistent expressions or lack annotations for first-time abbreviations (e.g., "CAM" refers to both Crassulacean Acid Metabolism and Dry Matter Yield). It is recommended to unify terminology usage and improve abbreviation annotations.
• Optimize figure and table presentation: Annotations for some figures (e.g., photosynthetic pathway diagrams) are overly brief, and "Key findings" in some tables are verbose. It is suggested to simplify figure annotations, refine core conclusions to improve readability, and add comparative charts of crop nutritional components (e.g., intuitive comparison of CP and lignin content across different crops) to enhance visualization.
• Strengthen the connection between conclusions and recommendations: The conclusion section provides insufficiently specific responses to identified challenges. It is recommended to refine actionable steps for solutions based on previously mentioned issues such as diseases and low protein content (e.g., simple disease prevention methods for smallholder farmers and low-cost protein supplementation schemes).

 

4. Supplement of Citations and Evidence

 

• Add latest research results: Many citations focus on pre-2020 literature. It is recommended to supplement recent studies from 2023 to 2025 (e.g., new findings on mycotoxin resistance in drought-tolerant crops and applications of novel processing technologies) to improve the timeliness of the review.
• Balance regional research citations: Current citations are dominated by studies from Africa and the Americas, with insufficient coverage of research in arid regions of Asia (e.g., northwest China, Central Asia). It is recommended to add research cases from these regions to enhance global applicability.

 

Author Response

Reviewer 3

Comment 1: This review features a significant research topic, rigorous structure, and substantial data support. It holds important reference value for the application of drought-tolerant crops in livestock feed and aligns with the publication orientation of the Animals journal. It is recommended for publication after the authors optimize the depth of content, supplement cutting-edge research directions, and add regional adaptability analysis.

Response: We are grateful to the reviewer for their insightful feedback and comments, which have significantly improved the quality of our manuscript. We are pleased that the reviewer recognized the relevance of our research topic, the rigor of our structure, and the strength of our data, as well as its value for the application of drought-tolerant crops in livestock feed; aligning well with the scope of Animals journal. The recommendation for publication motivated us to further refine the manuscript by addressing the reviewer’s comments. Although some comments were difficult to address due to limited information in literature, we have clearly explained and indicated the areas as future research studies that should be prioritised. We believe the revised manuscript now fully addresses all comments and suggestions and is ready for publication.

 

Comment 2: Optimization of Content Depth and Details

 Supplement regional adaptability analysis: Existing research cases cover regions such as Africa, the Americas, and Asia, but fail to clarify the preferred varieties and application differences of drought-tolerant crops across different climate zones (e.g., tropical arid zones vs. temperate arid zones) and farming models (large-scale intensive farming vs. smallholder subsistence farming). It is suggested to add region-specific discussions.

Response: Thank you for the valuable comment. The methodology applied in this review involved reviewing all studies on drought-tolerant crops regardless of region, and we established that most studies are from Africa, America, and Asia; hence, our review focused on those studies available in literature. So, due to the limited studies found in the highlighted regions, it was difficult to have a comprehensive comparison between the tropical arid and temperate arid zones. However, we appreciate the valuable comment, and thus we have commented on the distribution of studies found in our manuscript and how it is important to have studies from various regions to have comparisons and a broader overview of the application of drought-tolerant plants in animal feed. In addition, we have also commented on how the transition from subsistence farming to large-scale farming can promote these plants, as the current approach dwells more on subsistence. The literature is also silent on the preferred varieties, but based on the studies, the varieties that performed better in the reported studies were highlighted as preferred varieties either for adoption or use in further studies. Additional information (L144-149, L154-158) has been included to address the impact of drought on other regions and plant species. However, it should be noted that documented data regarding drought in these areas is very scarce.

 

Comment 3: Refine processing parameters: The manuscript mentions processing methods such as drying, ensiling, and grinding, but lacks integrated quantitative analysis of optimal parameters for key processes (e.g., suitable ensiling duration, optimal drying temperatures for different crops, and standard grinding particle sizes). It is recommended to supplement quantitative analysis of process-effect relationships.

Response: Thank you for the comment. We have incorporated additional quantitative data to further clarify the results and the relationship between measured parameters. Furthermore, we have expanded on the recommendations and addressed the consistencies and discrepancies identified across the referenced studies. For instance, under Drying, in L860, L861-862, L894-900 and L941 more data has been added to explain beyond just describing but adding meaning measurements and how they related to results. Additional process conditions and units have been added to bring more substance of drying conditions and its effects. Under Grinding and Pulverizing, similar revisions have been, changes can be tracked in L967-972, L974-975, L977-980, L984-987 and L990-993. For Ensiling, the suggested revisions have been made and can be tracked in L1030, L1035-1038, L1041 -1048 and L1065.

Comment 4: Strengthen research on synergistic application of multiple crops: Current research focuses primarily on single-crop utilization, with insufficient exploration of nutritional complementarity, palatability changes, and other effects of mixed feeding of multiple drought-tolerant crops (e.g., sorghum combined with cactus). It is suggested to add relevant discussions.

Response: We have incorporated the suggested changes by expanding our discussion on how hybrid formulations can complement drought-resistant crops to enhance animal feed quality. Furthermore, we highlight the scarcity of existing literature on this topic, underscoring a critical research gap (L511-529).

 

Comment 5: Expansion of Research Gaps and Cutting-Edge Directions:Supplement prospects of emerging technologies: Existing content focuses on traditional planting and processing technologies, with no coverage of the application prospects of cutting-edge technologies such as gene editing (e.g., developing high-protein drought-tolerant varieties) and microbial fermentation (e.g., compound probiotics to enhance nutrient conversion). It is recommended to add research prospects for these directions.

Response: Thank you for the insightful comment. We have added revised our discussion by adding the suggested emerging technologies as future directions. The revisions can be tracked in L1521-1525 and L1566-1568.

 

Comment 6: Improve environmental and economic assessments: The manuscript lacks systematic analysis of the carbon footprint, water consumption, and cost-effectiveness of drought-tolerant crop cultivation and feed production. It is suggested to supplement life cycle assessment or comparative economic benefit data to strengthen the sustainability argument.

Response: Thank you for your valuable feedback. To address this, we have included a table comparing economic and sustainability metrics such as carbon footprint, water use efficiency, yield, input costs, and economic returns. This data highlights the advantages of drought-tolerant crops to encourage their adoption and production. (Table 3, page 26).

 

Comment 7: Expand research on underutilized crops: For less-studied crops such as false banana (Ensete ventricosum), existing data are limited to specific regions (e.g., Ethiopia). It is recommended to supplement data on planting adaptability and feeding effects from more regions to enrich the range of crop options.

Response: According to the literature, there is little to no available data that further expands the use of underutilized crops such as false banana besides the provided information by the review.

 

Comment 8: Optimization of Expression and Structure: Standardize professional terminology: Some terms have inconsistent expressions or lack annotations for first-time abbreviations (e.g., "CAM" refers to both Crassulacean Acid Metabolism and Dry Matter Yield). It is recommended to unify terminology usage and improve abbreviation annotations.

Response: Abbreviations have been re-checked and updated throughout the manuscript.

 

Comment 9: Optimize figure and table presentation: Annotations for some figures (e.g., photosynthetic pathway diagrams) are overly brief, and "Key findings" in some tables are verbose. It is suggested to simplify figure annotations, refine core conclusions to improve readability, and add comparative charts of crop nutritional components (e.g., intuitive comparison of CP and lignin content across different crops) to enhance visualization.

Response: The photosynthetic pathway has been explained to the best detail possible in Figure 2 (page 7) and Figure 3 (page 8). The CP content has been expressed under low protein section (section 6.2), and an additional table (Table 5) has been supplemented to highlight some plants known to contain low CP, also the discussion covers the comparison of CP content between drought tolerant crops and other conventional crops in text. These discussions and a table can be found from L1212- 1269.

The lignin is a material well known to be high mostly in drought tolerant crops, hence the discussion of lignin indigestibility was added. Please refer to L1271- 1341.

 

Comment 10: Strengthen the connection between conclusions and recommendations: The conclusion section provides insufficiently specific responses to identified challenges. It is recommended to refine actionable steps for solutions based on previously mentioned issues such as diseases and low protein content (e.g., simple disease prevention methods for smallholder farmers and low-cost protein supplementation schemes).

Response: Comment accepted. The conclusion has been revised to bridge the gap between findings and actionable recommendations, providing clear and focused insights tailored for policymakers (L1521-1525, L1557-1561, L1566-1568).

 

Comment 11: Supplement of Citations and Evidence: Add latest research results: Many citations focus on pre-2020 literature. It is recommended to supplement recent studies from 2023 to 2025 (e.g., new findings on mycotoxin resistance in drought-tolerant crops and applications of novel processing technologies) to improve the timeliness of the review.

Response: The authors compiled the most recent studies available from the literature for this review; however, obtaining truly up-to-date data later than 2023 was difficult due to the limited extent of research on this research area.

 

Comment 12: Balance regional research citations: Current citations are dominated by studies from Africa and the Americas, with insufficient coverage of research in arid regions of Asia (e.g., northwest China, Central Asia). It is recommended to add research cases from these regions to enhance global applicability.

Response: Additional empirical studies covering drought impacts in Southeast Asia; specifically, Vietnam, Thailand, and the Philippines have been incorporated (see lines L144-149 and L154–158)

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have substantially improved their manuscript, and have addressed almost all of the reviewer’s concerns. Only a few issues remain.

Specific comments:

Fig.3: In the left-hand (“deacidification”) panel, the malic enzyme reaction converts malic acid to pyruvate, but the release of CO2 is not indicated, despite the importance of the CO2 budget in the overall pathways.

L287-288: The Latin binomials for these newly added plants should be provided.

L520: 2.0 CFU, or 2.0 log CFU?

L538: 2% on what basis? Certainly not on a DM basis. Do the authors mean 2% L. plantarum, i.e., 2 mL of an L. plantarum culture per 100 g of silage. If so, what is the concentration or density of the L. plantarum in the culture? Perhaps it would be better to express the inoculum as a log CFU per g of silage.

Fig. 8: Change “Conifery” to “Coniferyl”.

L1309: What is “226”?

Minor edits:

L292: Add “or maintain” after “enhance”.

L309: Change “nutritional” to “nutrient”.

L427: Change “tolerant” to “tolerance”.

L519: Change “cotton seed” to “cottonseed”.

L641-642: Change “horticulture” to “agronomy”.

L856: Change “animal” to either “animals” or “sheep”.

L966: Change “Pigs” to “pigs” (Also L1223).

L976: Change “higher to that of” to “to a greater extent than did”.

L1000: Insert “effect of” ahead of “particle size”.

L1335: Change “less” to “lower”.

Comments on the Quality of English Language

The manuscript is generally well-written, but some minor editorial suggestions are listed in the "Minor edits" in the Comments to Authors

Author Response

Reviewer 1

Specific comments:

Comment 1: Fig.3: In the left-hand (“deacidification”) panel, the malic enzyme reaction converts malic acid to pyruvate, but the release of CO2 is not indicated, despite the importance of the CO2 budget in the overall pathways.

Response: Figure 3 has been improved according to the suggested review comment. The release of CO2 to join Calvin cycle and used for the production of sugar molecules has been included.

Comment 2: L287-288: The Latin binomials for these newly added plants should be provided.

Response: The latin binomials have been included for other drought tolerant crops in L542-543.

Comment 3: L520: 2.0 CFU, or 2.0 log CFU?

Response. Thank you for highlighting, the 2.0 CFU has been fixed to 2.0 log CFU at L530.

Comment 4: L538: 2% on what basis? Certainly not on a DM basis. Do the authors mean 2% L. plantarum, i.e., 2 mL of an L. plantarum culture per 100 g of silage. If so, what is the concentration or density of the L. plantarum in the culture? Perhaps it would be better to express the inoculum as a log CFU per g of silage.

Response: Thank you for the comment. We agree with the reviewer that specifying the concentration of L. plantarum is vital for interpreting the study's results. While the authors noted using 2% of the total silage (50 kg), the lack of culture concentration details makes it impossible to calculate the final density or concentration in the methodology.  The sentence is now in L549.

Comment 6: Fig. 8: Change “Conifery” to “Coniferyl”.

Response: “Conifery” has been fixed to “Coniferyl” in Figure 8.

Comment 7: L1309: What is “226”?

Response: The number has been removed in L1346, it was an error.

Minor edits:

Comment 8: L292: Add “or maintain” after “enhance”.

Response: The phrase has been added as suggested in L296-297.

Comment 9: L309: Change “nutritional” to “nutrient”.

Response: “Nutrional” has been changed to “nutrient” as suggested in L316.

Comment 10: L427: Change “tolerant” to “tolerance”.

Response: “Tolerant” has been changed to “Tolerance” as suggested in L437.

Comment 11: L519: Change “cotton seed” to “cottonseed”.

Response: “Cotton seed” has been changed to “cottonseed” as suggested in L529 and L531.

Comment 12: L641-642: Change “horticulture” to “agronomy”.

Response: The word “horticulture” has been changed to “agronomy” as suggested in L675-676

Comment 13: L856: Change “animal” to either “animals” or “sheep”.

Response: The word “animal” has been changed to sheep in L890.

Comment 14: L966: Change “Pigs” to “pigs” (Also L1223).

Response: “Pigs” has been changed to “pigs” in L998 and L1259.

Comment 15: L976: Change “higher to that of” to “to a greater extent than did”.

Response: The phrase has been added as suggested in L1011.

Comment 16: L1000: Insert “effect of” ahead of “particle size”.

Response: The phrase has been added as suggested in L1035

Comment 17: L13: Change “less” to “lower”.

Response: The word “less” has been changed to “lower” as suggested in L1372.

Reviewer 2 Report

Comments and Suggestions for Authors

Abbreviations and full words should be used consistently. Check the main text, tables, and figures.

Table 1: what does "carbohydrates" refer to?

Table 1: what do you mean by "soybean" :  soybean meal or whole soybean?

Table 1: Include metabolizable energy.

Summarize Table 2 and remove unnecessary information.

In Table 2, what is the difference between "chickens" and "chicks"? Clarify this distinction in the table footnote.

Explanations for abbreviations, output variables, and intensity should be provided in the table footnote.

The use of abbreviations is recommended for Table 4.

Line 617: How does the use of AI and machine learning help? The current sentence is too general. Report findings from prior studies on AI and machine learning: What results have been reported, and what have previous studies focused on?

Line 1516: The sentence regarding the use of AI is vague and ambiguous. Provide a clearer and more detailed explanation.

I did not find a convincing answer to the following question: "Discuss whether governments subsidize producers or consumers to promote the development and adoption of these products". This is an important issue and should be addressed carefully and explicitly.

For comment 9 (from the previous review), the response is not convincing.

Which term will you use consistently throughout the manuscript: "maize" or "corn"?

Author Response

Review 2

Comment 1: Table 1: what does "carbohydrates" refer to?

Response: Thank you for the comment. The word “carbohydrates” has been revised to “carbohydrate” in Table 1.

Comment 2: Table 1: what do you mean by "soybean" :  soybean meal or whole soybean?

Response: Thank you for your comment. The proximate components listed in the table refer specifically to soybean meal. We have updated the table terminology to ensure better clarity Table 1).

Comment 3: Table 1: Include metabolizable energy.

Response: Metabolizable energy included as recommended in table alongside supporting references.

Comment 4: Summarize Table 2 and remove unnecessary information.

Response: Unnecessary information has been removed and summarized, as well as the addition of abbreviations in the footnote, as highlighted red in the table and footnote.

Comment 5: In Table 2, what is the difference between "chickens" and "chicks"? Clarify this distinction in the table footnote.

Response: The authors have revised the table and chose to remain with “chickens” for consistency. The studies cited started the experiments with chicks but reported the results on grown chickens during production phases.

Comment 6: Explanations for abbreviations, output variables, and intensity should be provided in the table footnote.

Response: The footnote in Table 2 has been revised to the greatest extent of detail possible. Additional abbreviations have been included and grouping of output variable according to animal performance indices have been included. Additional sentence explaining intensities of the tested animal feed diets has been provided. Additional indices have been referred to in the table as they cannot all be explained in the footnote due to length.

Comment 7: The use of abbreviations is recommended for Table 4.

Response: Abbreviation has been added in Table 4 and expanded in the footnote.

Comment 8: Line 617: How does the use of AI and machine learning help? The current sentence is too general. Report findings from prior studies on AI and machine learning: What results have been reported, and what have previous studies focused on?

Response: Recent studies incorporating remote sensing, RGB imagery, and machine learning/AI have been added, alongside a new review on AI-driven assessment of crop performance under drought conditions. Furthermore, the advantages of using machine learning to generate reliable data on drought tolerance, yield, biomass, and growth for alternative feed crops was highlighted. This approach provides crucial evidence of resilience to stakeholders, thereby promoting the adoption of these crops. The changes can be tracked in L633-653.

Comment 9: Line 1516: The sentence regarding the use of AI is vague and ambiguous. Provide a clearer and more detailed explanation.

Response: The sentence regarding the use of AI has been revised with clearer practical approaches of using machine learning to predict precise nutritional profiles of feed rations and their consequent results in animal systems. The changes can be tracked in L1578-1583.

Comment 10: I did not find a convincing answer to the following question: "Discuss whether governments subsidize producers or consumers to promote the development and adoption of these products". This is an important issue and should be addressed carefully and explicitly.

For comment 9 (from the previous review), the response is not convincing.

Response: In response to the reviewer’s comment, we have expanded the discussion on the roles of government and non-governmental institutions at both national and international levels in supporting the adoption and production of drought-tolerant crops, with examples from different countries across the world. These updates are reflected in L1476–1489 and L1501–1517.

Comment 11: Which term will you use consistently throughout the manuscript: "maize" or "corn"?

Response: The authors have resorted in using maize for consistency.