Meta-Analysis of Dietary Supplementation with Seaweed in Dairy Cows: Milk Yield and Composition, Nutrient Digestibility, Rumen Fermentation, and Enteric Methane Emissions
, Alejandro Lara-Bueno 1, Germán David Mendoza-Martínez 2, Luis Alberto Miranda-Romero 1, Gabriela Vázquez Silva 3, María Eugenia de la Torre-Hernández 4, Nallely Sánchez-López 2 and Pedro Abel Hernández-García 5,*
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe study uses a meta-analysis approach to summarise the existing state of knowledge on the use of seaweed as an ati-metanogenic additive in dairy cows. The study was well designed and followed approved standards. Authors need to exercise more retraint and allow the result speak for itself. The narratives are in many intances, contradictory to the result presented. THis and a few other comments are recommended for correction.
Abstract: In Line 24/25, authors reported that seaweed decreased dry matter intake but concluded the abstract in line 34/35 that seaweed reduced methane without affecting dry matter intake. This is inconsistency.
Line 49-50: This statement appear emphatic meanwhile Line 68-72 showed a nuanced perspective of the state of literature on seaweed as a methane mitigating agent. Authors are advised to streamline the introduction section accordingly.
Experimental design: rotative or continuous. Will latin square/ cross over design vs CRD/continuous appear clearer? It will be important to provide clearer description of what the experimental designs are.
Table 2: Label the two P-values differently and define each.
Abbreviations like DMI, MY, etc. can be written in full. It makes it easier for reader without having to navigate the legend.
Line 241-247: These sentences can be fused into the relevant sections narrating Table 2 and 3. Authors will force their reader to go back to Table 2 and 3 separately to appreictae this additional information. Move it around.
L249: covariate of experimental design
L306: Here is another inconsistent statement that contradicts the data. It appears authors are trying to force their data to say what did not manifest.
L307-320: This section ought to provide some insight into the differences in the bioactivity of the red vs brown seaweed and how this may affect their ability to reduce dry matter intake. What are the anti-palatability factors- phluorotannins?
L321-325: it appears that reduced DMI may not be explained by reduced bacteria and rumen fermentation as digestibility of DM, CP, NDF was not affected significantly. Nevertheless, it could be a factor, among others, but authors should be clearer on this.
L378/379: due to the presence of plant secondary metabolites which exerts differential antimicrobial properties. It is safer to simply say seaweed does reduce scc rather the more bogus attempt to suggest it as a strategy to improve udder health and milk quality.
L383: dairy ruminants?. Dairy cows or simply ruminants would be better
L392-394: what is the range of iodine content in milk from the meta-analysis? Provide this specificity to buttress the discussion.
Conclusion: see previous comments.
L467-467: there is no evidence of this in the data.
Comments on the Quality of English Language
The quality of language writing is good. Only few minor corrections are observed.
Author Response
Response to Reviewer #1:
We would like to thank the reviewer for the careful and thorough reading of this manuscript and for the thoughtful comments and constructive suggestions, which help to improve the quality of this manuscript. Our response follows:
Comments and Suggestions for Authors
The study uses a meta-analysis approach to summarise the existing state of knowledge on the use of seaweed as an ati-metanogenic additive in dairy cows. The study was well designed and followed approved standards. Authors need to exercise more retraint and allow the result speak for itself. The narratives are in many intances, contradictory to the result presented. THis and a few other comments are recommended for correction.
Comment 1. Abstract: In Line 24/25, authors reported that seaweed decreased dry matter intake but concluded the abstract in line 34/35 that seaweed reduced methane without affecting dry matter intake. This is inconsistency.
Response: This inconsistency has been corrected on line 35
Comment 2. Line 49-50: This statement appear emphatic meanwhile Line 68-72 showed a nuanced perspective of the state of literature on seaweed as a methane mitigating agent. Authors are advised to streamline the introduction section accordingly.
Response: These are two different things. In any introduction to a scientific article, it is essential to maintain an orderly sequence, starting with the general and ending with the specific, as shown in the present manuscript. In lines 49-50, it is generally mentioned that seaweeds are a more effective alternative for mitigating methane, but only in a general way. Subsequently, in lines 69-72, a deep (specific) analysis of the effect of seaweeds in mitigating methane is made. The contradictory effects between studies mentioned in lines 69-72 do not diminish the antimethanogenic potential of seaweeds but only show that the effects may vary between studies (which is expected considering the different experimental conditions). Therefore, we disagree that changes are required in the introduction. Furthermore, no specific changes were indicated.
Comment 3. Experimental design: rotative or continuous. Will latin square/ cross over design vs CRD/continuous appear clearer? It will be important to provide clearer description of what the experimental designs are.
Response: Dear reviewer, using continuous and rotating is the clearest and most commonly used way to classify experimental designs of studies. Below, we list some meta-analyses that used this classification:
Orzuna-Orzuna, J. F., Dorantes-Iturbide, G., Lara-Bueno, A., Mendoza-Martínez, G. D., Miranda-Romero, L. A., & Hernández-García, P. A. (2021). Effects of dietary tannins’ supplementation on growth performance, rumen fermentation, and enteric methane emissions in beef cattle: A meta-analysis. Sustainability, 13(13), 7410.
Torres, R. N. S., Ghedini, C. P., Paschoaloto, J. R., da Silva, D. A. V., Coelho, L. M., Junior, G. A., ... & Almeida, M. T. C. (2022). Effects of tannins supplementation to sheep diets on their performance, carcass parameters and meat fatty acid profile: A meta-analysis study. Small Ruminant Research, 206, 106585.
Torres, R. D. N. S., Bertoco, J. P. A., de Arruda, M. C. G., de Melo Coelho, L., Paschoaloto, J. R., de Almeida Júnior, G. A., ... & Almeida, M. T. C. (2021). Meta-analysis to evaluate the effect of including molasses in the diet for dairy cows on performance, milk fat synthesis and milk fatty acid. Livestock Science, 250, 104551.
Also, it is not necessary to specifically describe each experimental design since it is not the objective of the present study. In addition, the reference for each article included in the database was added in Table 1, and each reader can consult them if he/she is curious about other particular details.
Comment 4. Table 2: Label the two P-values differently and define each.
Response: This information has been specified in lines 204 and 223. Also, in Tables 2 and 3 a space was added between columns to clarify what the P value is for the WMD and for the heterogeneity test.
Comment 5. Abbreviations like DMI, MY, etc. can be written in full. It makes it easier for reader without having to navigate the legend.
Response: DMI and MY are abbreviations used worldwide to abbreviate dry matter intake and milk yield, respectively. Therefore, it is not necessary to add the full name.
Comment 6. Line 241-247: These sentences can be fused into the relevant sections narrating Table 2 and 3. Authors will force their reader to go back to Table 2 and 3 separately to appreictae this additional information. Move it around.
Response: This problem has been fixed. We moved the information to lines 200-201 and 216-222. With this change, the result descriptions are now close to each result table, and returning to each table is no longer necessary.
Comment 7. L249: covariate of experimental design
Response: This change has been made on line 257.
Comment 8. L306: Here is another inconsistent statement that contradicts the data. It appears authors are trying to force their data to say what did not manifest.
Response: Dear reviewer, please review carefully. Table 2 shows that DMI had a p-value = 0.113, which clearly shows that seaweeds did not affect DMI. Subgroup analyses were then performed in which some seaweed species did affect DMI, but that description is further clarified in lines 308-309. The meta-analysis should follow a sequence from overall findings to subgroups, and this sequence is shown in the discussion section.
Comment 9. L307-320: This section ought to provide some insight into the differences in the bioactivity of the red vs brown seaweed and how this may affect their ability to reduce dry matter intake. What are the anti-palatability factors- phluorotannins?
Response: Dear reviewer, please review carefully. Adding information on the bioactivity of red and brown seaweeds was exactly what we showed in this section (lines 310-321). Specifically, bioactivity in the rumen microbiota is mentioned, which could be related to digestibility and passage time of feed in the rumen. These effects are particularly important because they relate directly to changes in DMI in ruminants.
Comment 10. L321-325: it appears that reduced DMI may not be explained by reduced bacteria and rumen fermentation as digestibility of DM, CP, NDF was not affected significantly. Nevertheless, it could be a factor, among others, but authors should be clearer on this.
Response: Thanks for the suggestion. We have removed the word "directly", and now the sentence only mentions that it "could" be related.
Comment 11. L378/379: due to the presence of plant secondary metabolites which exerts differential antimicrobial properties. It is safer to simply say seaweed does reduce scc rather the more bogus attempt to suggest it as a strategy to improve udder health and milk quality.
Response: Thanks for the suggestion, this change has been fixed on line 387.
Comment 12. L383: dairy ruminants?. Dairy cows or simply ruminants would be better
Response: This change has been made, line 391.
Comment 13. L392-394: what is the range of iodine content in milk from the meta-analysis? Provide this specificity to buttress the discussion.
Response: Thanks for the suggestion. The range of iodine content in milk has been added in line 401.
Comment 14. Conclusion: see previous comments.
L467-467: there is no evidence of this in the data.
Response: The results obtained fully support the entire conclusions section, and you can verify this by carefully reviewing all the Tables and Figures again. Therefore, the reviewer is wrong to mention that there is no evidence.
Comment 15. Comments on the Quality of English Language
The quality of language writing is good. Only few minor corrections are observed.
Response: Thank you!
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsBasically, I do not agree that agriculture, including livestock production, is currently held responsible for GHGs emissions (all GHGs and not just CH4). It would have been worthwhile to devote some word to the exact numbers regarding the total GHGs emissions of the world, of which, according to some literature, agriculture accounts for 18-20%, within which livestock production accounts for 7-8%.
The main comments are focusing on the amount and dosage of supplementing seaweed. Refinement of the conclusions is recommended.
I don't know what would be the right expression but using the words "current/recent study" (L 399; L 422; L 433) can be deceptive, referred to the methodology.
Further comments are included in the attached document.
Comments for author File: Comments.pdf
Author Response
Response to Reviewer #2:
We would like to thank the reviewer for the careful and thorough reading of this manuscript and for the thoughtful comments and constructive suggestions, which help to improve the quality of this manuscript. Our response follows:
Comments and Suggestions for Authors
Basically, I do not agree that agriculture, including livestock production, is currently held responsible for GHGs emissions (all GHGs and not just CH4). It would have been worthwhile to devote some word to the exact numbers regarding the total GHGs emissions of the world, of which, according to some literature, agriculture accounts for 18-20%, within which livestock production accounts for 7-8%.
Response: Dear reviewer, the introduction of this manuscript specifies that the GHG figures are for the whole world but only for dairy farms. This information was justified from the first version of our manuscript on lines 43.44, with the following sentence:
“Bačėninaitė et al. [3] indicate that CH4 emitted by dairy cows contributes approximately 35–55% of total greenhouse gas (GHG) emissions from dairy farms worldwide”
The total world GHG emissions amounts were not aggregated as they may confuse the reader. Furthermore, this is justified because our study only assessed emissions in dairy cows, and adding information on emissions from other agricultural sectors can be confusing.
Bačėninaitė, D.; Džermeikaitė, K.; Antanaitis, R. Global warming and dairy cattle: How to control and reduce methane emission. Animals 2022, 12, 2687. https://doi.org/10.3390/ani12192687
Comment 1. The main comments are focusing on the amount and dosage of supplementing seaweed. Refinement of the conclusions is recommended.
Response: Thank you for your comment. We reviewed the amount and dosage of seaweed supplementation again but found no errors. We also reviewed the conclusions again but found no errors, as they are supported by the results obtained.
Comment 2. I don't know what would be the right expression but using the words "current/recent study" (L 399; L 422; L 433) can be deceptive, referred to the methodology.
Response: We have reviewed lines 399, 422, and 433 again and have found no errors. In lines 399 and 422, the phrase "In the current study" is used because it starts a paragraph by briefly stating the present study's findings. This type of phrase is widely used in scientific articles to indicate that the information mentioned refers to the findings obtained in the manuscript and not in other studies. Therefore, we confirm that the phrases are correct and not misleading.
On the other hand, in line 433, the phrase "A recent study" is used, and after the phrase, the citation of the scientific article to which it refers is added. This phrase is also widely used to cite the findings of other authors. Therefore, we disagree that this phrase is misleading because a scientific reference duly supports it.
Comment 3. Further comments are included in the attached document.
Below are the comments added to the attached document and their responses.
Comment 4. L139-The year of the publication is not mentioned in Table 1. It is recommended to add.
Response: The full reference, including the year, was added in Table 1. Unfortunately, the Dairy Journal format dictates that the reference year must be replaced by a continuous reference number, which prevents the year from being visible in Table 1. Furthermore, this information is not relevant to the analysis and results; it is only used to sort the database in the Microsoft Excel sheet.
Comment 5. L186- Have the following factors that may affect the results been taken into account?
- Number of animals in different trials (effect on statistical differences);
- Number of lactations;
- Effect of genotype (e.g. Holstein Freisian vs. Sahiwal);
- etc.
Response: The factors mentioned by the reviewer were not included in the present meta-analysis as some previous studies (Sofyan et al., 2022; Lean et al., 2021) indicate that they are not relevant to the effects of seaweed on ruminants. Also, other factors, such as lactation number, were not reported in a sufficient number of articles, which prevented them from being included in the meta-regression.
Lean, I. J., Golder, H. M., Grant, T. M., & Moate, P. J. (2021). A meta-analysis of effects of dietary seaweed on beef and dairy cattle performance and methane yield. PLoS One, 16(7), e0249053.
Sofyan, A., Irawan, A., Herdian, H., Harahap, M. A., Sakti, A. A., Suryani, A. E., ... & Jayanegara, A. (2022). Effects of various macroalgae species on methane production, rumen fermentation, and ruminant production: a meta-analysis from in vitro and in vivo experiments. Animal Feed Science and Technology, 294, 115503.
Comment 6. L263-Table 5.
Response: This change has been made.
Comment 7. -308-That's why the correct dosage is very important, both in micro- and macroalgae supplementation. A larger than recommended dose may also cause decreased DMI, fat content and MY.
Response: This comment is correct, we fully agree. It is very important to properly define the dosages when using macroalgae and microalgae.
See the comment at section "Conclusions".
Response: Dear reviewer, Due to the wide variety of seaweed species, it would be too risky to recommend a generalized dose of seaweed. Therefore, we consider that more studies on the different seaweed species are required to establish recommendations on the best dose for each one.
Comment 8. L326- Italic
Response: This change has been made, please see line 334.
Comment 9. L463- It can be hazardous to draw general conclusions from a comparison of studies in which climatic conditions, housing systems, level of feeding, breeds, level of production and many other factors differ.
Nevertheless, the chosen methodology is the best way to eliminate the differences.
How could you resolve this kind of contradiction?
Response: As you mentioned, meta-analytical statistical procedures are the best option to resolve this type of variation in experimental conditions between studies. Therefore, the conclusions of the present study are valid since they are based on results obtained with meta-analytical statistical procedures.
Comment 10. L474- What is the recommended dose or percentage of seaweed supplementation in dairy cows' diet? An average value (e.g. based on liveweight) would be a very informative for the farmers.
Response: Dear reviewer, Due to the wide variety of seaweed species, it would be too risky to recommend a generalized dose of seaweed. Therefore, we consider that more studies on the different seaweed species are required to establish recommendations on the best dose for each one.
Author Response File: Author Response.pdf
