Nutritive and Fermentative Traits of African Stargrass (Cynodon nlemfuensis Vanderyst) Forage Preserved for Silage and Haylage

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study aimed to evaluate the potential of African star grass preserved as silage or haylage to fill the gaps in forage in Costa Rica. The relatively high yield potential and low cost of establishment of star grass is of significance for the development of animal husbandry in developing countries. Therefore, to some extent, the topic of this manuscript seems to be interesting and meaningful for some places and readers. However, several issues required to be addressed.

 

1. There are many studies on the topic of silage or hay development, so the novelty is unclear.

2.There are many detailed mistakes in the full text, such as improper use of spaces, repeated abbreviations (for example, NIRS), inconsistent writing of P value, etc..

3. For methodology, all nutritive parameters were analyzed using a Foss 2500 near-infrared spectroscopy machine (NIRS) and the NIRS Forage and Feed Testing Consortium equation? These parameters are predictive, which is not suitable for research papers and needs to be measured in other methods. Also, the analyses of buffering capacity and ammonia nitrogen should be described in detailed.

4. For haylage making, ensiling period should not be used in all tables and figures, please modify.

5. For Fig. 3 and 4, 18-week period including 9 weeks, Why temperature data requires two figures? Please explain.

6. Please uniform the unit of preservation period. Weeks or days, choose one.

7. Please explain the intention of using PCA, it seems that there is no meaning from the manuscript. Correlation analysis will be more appropriate.

8.Rather than just describing the results, the discussion section needs to explain the reasons in depth and mine information.

9. Please check and correct the format of references according to the journal's author guidelines.

 

Comments on the Quality of English Language

Moderate editing of English language required.

Author Response

1. There are many studies on the topic of silage or hay development, so the novelty is unclear. We added a justification in the last paragraph of the Introduction (line 73) to clarify the novelty and the relevance of the topic of the article.
2. There are many detailed mistakes in the full text, such as improper use of spaces, repeated abbreviations (for example, NIRS), inconsistent writing of P value, etc. We checked the whole manuscript and edited those according to the suggestion.
3. For methodology, all nutritive parameters were analyzed using a Foss 2500 near-infrared spectroscopy machine (NIRS) and the NIRS Forage and Feed Testing Consortium equation? These parameters are predictive, which is not suitable for research papers and needs to be measured in other methods. Also, the analyses of buffering capacity and ammonia nitrogen should be described in detailed. NIRS is nowadays a widely technique used in research papers. The NIR Forage and Feed Testing Consortium has the most robust equations in the market with samples from different parts of the world and environments. The authors have published papers where those equations were used (https://doi.org/10.1002/agj2.20806, https://doi.org/10.1002/cft2.20084, and https://www.nacaa.com/file.ashx?id=e3a5523e-7520-4cdf-ab97-d901f93d7b53; also attached). Both the Forage Lab at Mississippi State and the Forage Lab at the University of Costa Rica are certified in the National Forage Testing Association (https://www.foragetesting.org/_files/ugd/24f64f_3e42dad1cfd74595979b18d9e3e3ed63.pdf). In line 159 and 160 we referenced the methodology for buffer capacity and ammonia nitrogen analysis.
4. For haylage making, ensiling period should not be used in all tables and figures, please modify. We corrected for haylage the tables and figures, instead of use “ensiling period” we used “Preservation period”.
5. For Fig. 3 and 4, 18-week period including 9 weeks, Why temperature data requires two figures? Please explain. In lines 111–116 we explained the reason to include two figures because we had three 8-channel thermocouples that stored the temperature data that allowed us to make the data more robust along the weeks of preservation.
6. Please uniform the unit of preservation period. Weeks or days, choose one. For temperature we used weeks as it is a continuous data series, whereas days was used as a categorical variable of the treatments.
7. Please explain the intention of using PCA, it seems that there is no meaning from the manuscript. Correlation analysis will be more appropriate. With the PCA we aimed to simplify, visualize, and recognize different patterns in the data, because we had a large data set with many variables per treatments.
8. Rather than just describing the results, the discussion section needs to explain the reasons in depth and mine information. The journal guidelines divide the research articles into different sections. The results describe the outcome of the experiment, and the discussion explains the reasons for the results with the support of other investigations, and so we did in the discussion.
9. Please check and correct the format of references according to the journal's author guidelines. We corrected the format, according to the journal requirements. Also, the journal staff adjusted the document accordingly.

Reviewer 2 Report

Comments and Suggestions for Authors

   The content of major nutrients and their digestive parameters were estimated by NIR technique. However, if the prediction equations used were not developed specifically for the Star grass silage and/or haylage (certified /validated), the predictive data should not be used for scientific research purposes. The authors should obtain nutritive values by standard methods (e.g. AOAC methods) and re-analysis the data.

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

1. The content of major nutrients and their digestive parameters were estimated by NIR technique. However, if the prediction equations used were not developed specifically for the Star grass silage and/or haylage (certified /validated), the predictive data should not be used for scientific research purposes. The authors should obtain nutritive values by standard methods (e.g. AOAC methods) and re-analysis the data. We appreciate your suggestion. NIRS is nowadays a widely technique used in research papers. The NIR Forage and Feed Testing Consortium has the most robust equations in the market with samples from different parts of the world and environments. The authors have published papers where those equations were used (https://doi.org/10.1002/agj2.20806, https://doi.org/10.1002/cft2.20084, and https://www.nacaa.com/file.ashx?id=e3a5523e-7520-4cdf-ab97-d901f93d7b53; also attached). Both the Forage Lab at Mississippi State and the Forage Lab at the University of Costa Rica are certified in the National Forage Testing Association (https://www.foragetesting.org/_files/ugd/24f64f_3e42dad1cfd74595979b18d9e3e3ed63.pdf).

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Haylage is fermented hay that is produced by mowing grasses at the right time. The process of making haylage is a multi-step process, so it is advisable to become thoroughly familiar with the specifics of this production. Knowledge of the individual steps then significantly affects the nutritional quality of the prepared feed.

To make sure your haylage reaches the right values, it's a good idea to gain experience in making normal silage beforehand.

Haylage is a roughage that contains more than 50% dried matter. This is about 20% more than normal silage. The differences between silage and haylage can also be seen on the production level. In the case of haylage, the timing of the grass harvest is extremely important. Mowing at the right time ensures that the raw material achieves excellent quality and is rich in a number of essential nutrients. Early-mowed green fodder is more acidic and has more valuable components than late-mowed, mature grass. However, harvesting too early reduces the energy value and generates a level of acidity that may be reluctantly taken up by game. Excessive drying, on the other hand, hinders compaction and can generate mold. Thick stalks prevent the formation of impermeable bales.

The development of mold and the presence of bacteria on mowed grasses are aspects that unfortunately very often hinder the haylage production process. However, the disadvantages that can be observed with this solution are manageable. To make sure that the haylage does not contain an increased number of harmful microorganisms in the composition, special attention should be paid to temperature and evaporation time. Avoiding the development of mold is an aspect that should be taken care of at the harvest stage - the thicker the stalks, the more likely the permeability of the bales will cause mold processes.

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The article submitted for review meets the requirements of the publisher. The layout of the chapters is correct. The citation of literature and its compilation are not objectionable. The graphic presentation is clear. The discussion is written in a correct manner.

Please make any corrections to the following lines:

line 48-replace the word “silage” with “ensilage”

line 49-is “soluble carbohydrates” should be “water soluble carbohydrates” WSC

line 108-Lactobacillus – can the authors specify the genera of Lactobacillus?

 

 

I believe that after small corrections the work can be published.

Author Response

1. We appreciate the input given by Reviewer 3. Because of the difference between the content of DM of haylage compared to silage in tropical conditions, is very difficult to reach a silage with 30% DM specially with tropical grasses as African Star grass. 50% DM in haylage we can have with other grasses as Transvala (Digitaria decumbens) that the morphology is suitable to drier quickly.
2. Line 48-replace the word “silage” with “ensilage”. We replaced the word “silage” with “ensilage” in line 48
3. Line 49-is “soluble carbohydrates” should be “water soluble carbohydrates”. We replaced soluble carbohydrates” with “water soluble carbohydrates” WSC in line 49.
4. Line 108-Lactobacillus – can the authors specify the genera of Lactobacillus? The analysis we made for the Lactobacillus didn´t identify the species but accounted for the total concentration of bacteria belonging to the Lactobacillus We have changed it to “Lactobacillus spp”.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors This manuscript, which I have reviewed before, evaluates the potential of African star grass preserved as silage or haylage to fill the gaps in forage in Costa Rica. Generally, for some comments, the authors have done a good job of revising their manuscript according to the reviews. I have a couple of points to raise that should be addressed. In particular, the authors should discuss some of the limitations of their study. This is not a fatal criticism, as scientific works commonly have limitations and shortcomings. However I feel that these are not suitably discussed in the revised manuscript. Please address the following points: 1. Comment 3 regarding NIRS analysis: The authors should acknowledge and discuss in their manuscript that the outcome of NIRS is predictive, not real. The usage of this technique in other published studies does not change this fact, and since it is a limitation of the current work, it should be mentioned and discussed in the manuscript so that readers are aware of this potential limitation. I am not asking that the authors re-analyze their data, but simply that they mention and discuss this point. 2. Comment 4 regarding the usage of "ensiling period": In the captions of Figure 2 and 4, "ensiling period" is still used, please check it throughout the manuscript. 3. Comment 5 regarding the data of temperature, why the temperature was not recorded for silage and haylage treatments at other two periods (45 and 90 d). 4. Comment 6 regarding the uniformity of the preservation period unit: For temperature, even if you use days, it's still a continuous data series. 5. Comment 8 regarding the improvement of the Discussion section: There was no change in the discussion. Please improve it. 5. Comment 9 regarding the format of the Reference section: The format of references is still incorrect according to the journal's author guidelines.

The author should pay enough attention to the review comments, rather than perfunctory. Comments on the Quality of English Language

Extensive editing of English language required.

Author Response

1. We acknowledge that NIR is a predictive technique, however, we used validated equations in this study to run the samples collected. We added the following paragraph in lines 153-157: “NIR is widely used for routine forage analysis in commercial laboratories [26],[27], allowing to predict the nutrient composition of forages based on a regression against a reference method from established data from wet chemistry samples. The data in this study have been validated, and regression and validation confidence intervals were used to ensure the predictability of the samples with low bias and standard error of prediction.” to clarify usage, importance, and predictive nature of the NIRS.
2. Usage of “ensiling period”: in line 222 and 270 we changed the word ensiling for preserving, and we checked throughout the manuscript, instead of ensiling we used preserving.
3. Data of temperature: we added in lines 114-119 the following paragraph: “Temperature was measured using thermocouples programmed for 30-minute intervals, with which we could collect 2880 and 5760 data points per sensor, in all bags at 60 and 120 d (24 bags), respectively. From all the 60 and 120 d bags, we had roughly 34560 and 69120 data points, respectively, during the preserving period. By having this robust database, we had a better perspective of the other two treatments (45 and 90 d).” to explain why the temperature was not recorded to all the periods but we had enough data points to draw a good picture of the temperature during the experiment.
4. Uniformity of preservation period unit: we added in lines 168-170 the following paragraph: “Temperature was measured as a continuous variable over time, while the preservation periods were treated as categorical variables using specific time intervals (45, 60, 90, and 120 d).” We appreciate this comment, and we understand why the use of two different units (days and weeks) in the manuscript might be confusing. We hope that along with the explanation given in lines 114-119 and this last paragraph (lines 168-170), we have given enough details of the different use of units for the nutritional and fermentative variables (categorical treatments) versus the temperature (continuous data).
5. Improvement of the discussion section. We have worked on the discussion section and improved it with more discussion and relevant references (highlighted in the document)
6. The format of reference section: We understand that there might have been changes in the reference section. However, we have been using the last version provided by the journal for the two revisions. Our understanding is that the journal makes a final formatting check before publishing.

Author Response File: Author Response.pdf