Nitrogen Intake and Its Partition on Urine, Dung and Products of Dairy and Beef Cattle in Chile

Round 1

Reviewer 1 Report

The authors consolidated research data to estimate N partitioning in different Chilean cattle systems. The authors discussion is clear and relevant to current trends in environment and animal science. The article identifies useful differences between pasture and conventional systems. The article provides inadequate statistical evidence, particularly in the data presentation in tables and figures. Calculation of nitrogen partitioning is flawed. Specific recommendations are indicated below.

Lines

94-96: Unclear what the search terms were. Did the keyword search include both and animal purpose and production system or were they searched independently? How many articles/abstracts/theses were screened?

139-142: Equations were used to estimate 86% of the N partitioning data? I'm unsure what the authors intend in this sentence.

141: "... throughout spot of urine and dung..." Unclear

166-167: Was it forward or backwards stepwise selection? Something else?

312-314: These statistics are inadequate. At minimum, P-values and ρ or r² values should be included (depending on if it is correlation or regression). For the multiple effects models, p-values and selection criterion should be added to table 7. 

327-329: ADF is not a measure of lignification alone. The effect of cellulose should also be considered.

339-341: Same comment as lines 312-314. 

381-382: Same comment as lines 139 - 142. How much of the data was reported in studies and how much was estimated?

Figure 1. Please modify this figure to indicate how many studies in each category were screened. How many studies passed selection criteria? Consult the PRISMA Guidelines for suggested formatting (Page et al., 2021 BMJ 372:n71).

Table 1. Check equations for Total N Intake and Milk N. Typically feed uses a N correction factor of 6.25 and milk 6.38. The model for Total N Excretion is missing key factors: N retained for animal requirements (maintenance, growth, reproduction). Milk N should include both nitrogen from milk protein and MUN.

Table 3. Is this a count of articles that reported the variables? Only some of this information is shown in Figure 2. The authors can greatly improve the table by adding summary statistics of the variables used in model selection (e.g., a table that reports means, variation, number of observations, etc.). 

Table 5. Did the different systems, stage of lactation, or season affect milk N? 

Figures 3 and 4. Statistical information must be added to the graphs. Was the intent correlation or regression?

Figure 3a, 3c. Is there any commonality if the outliers?

Author Response

REVIEWER 1
Dear reviewer
First of all, we really appreciate your thorough review in terms of grammar and information, which allowed us to improve the quality of manuscript. We have attended all of your comments, using track changes in Word. An answer for each comment was included, as described below.
Best regards
Ignacio Beltrán
Correspondence author

ANSWERS TO REVIEWER 1
Comments and Suggestions for Authors
The authors consolidated research data to estimate N partitioning in different Chilean cattle systems. The authors discussion is clear and relevant to current trends in environment and animal science. The article identifies useful differences between pasture and conventional systems. The article provides inadequate statistical evidence, particularly in the data presentation in tables and figures. Calculation of nitrogen partitioning is flawed.

Specific recommendations are indicated below.
Lines
94-96: Unclear what the search terms were. Did the keyword search include both and animal purpose and production system or were they searched independently? How many articles/abstracts/theses were screened?
• Answer 1. We used a combination of two keywords: 1) Animal purpose (beef or dairy cattle) plus 2) Production System (grazing, grazing and supplementation and confinement system). We have edited text to clarify the use of keywords.
• Answer 2. We screened 72 studies (56 and 16 for dairy and beef cattle, respectively). However, we did not include all of the them in the data analysis, mainly related to lack of information. We included a sentence in results (Line 109-112).

139-142: Equations were used to estimate 86% of the N partitioning data? I'm unsure what the authors intend in this sentence.
• Answer. We have edited text to clarify the use of equations. Please, check Line 165-169

141: "... throughout spot of urine and dung..." Unclear
• Answer. We have edited the text. Check Line 165-169.

166-167: Was it forward or backwards stepwise selection? Something else?
• Answer. We used forward stepwise selection. Text was edited to clarify statistical method. Line 197.

312-314: These statistics are inadequate. At minimum, P-values and ρ or r2 values should be included (depending on if it is correlation or regression). For the multiple effects models, p-values and selection criterion should be added to table 7.
• Answer 1. According to reviewer comments, variables influencing NUE were evaluated independently in uni-variables models, which included the fixed effect of each variable and random effect of experiment ID. A sentence was included in statistical analysis (Line 206-209) and marginal R2 of uni variable models were included in the text. Similar procedure was carried out for variables influencing urinary N excretion. Please, check Lines 382-384 and 411-412.
• Answer 2. P-value of models were included in the table 7. Selection criteria was included as footnote in the table.

327-329: ADF is not a measure of lignification alone. The effect of cellulose should also be considered.
• Answer. We have removed the sentence related to lignification and we have focused in the effects of full ADF structure on NUE instead of individual components, as reported in the metanalysis by Phuong et al. (2013). Line 399-401.

339-341: Same comment as lines 312-314.
• Answer. R2 was included for variables as suggested.

381-382: Same comment as lines 139 - 142. How much of the data was reported in studies and how much was estimated?
• Answer. 14% of urinary N excretion data entered in the database was measured in the studies (using spot samples). Therefore, 86% of urinary N excretion data was calculated using equation, which could reduce the accuracy of results. We encourage to re-searcher to include N measurements from full urine collection or spot samples. See Lines 458-463.

Figure 1. Please modify this figure to indicate how many studies in each category were screened. How many studies passed selection criteria? Consult the PRISMA Guidelines for suggested formatting (Page et al., 2021 BMJ 372: n71).
• Answer. We appreciate the referee suggestion to include the number of studies in each category in the figure. However, Figure 1 was included to give a graphical representation of data collation process. We used (as example) the figure reported by Beltran et al. 2021, published in Journal of Environmental Quality (DOI: https://doi.org/10.1002/jeq2.20186). We have maintained the figure 1 as submitted, however, we think reviewer comments is relevant, therefore, we have included a sentence explaining the total data, giving a context on included and excluded data, using the information reported by Page et al. (2021) (Fig.1 in the article). Please, check Line 222-225.

Table 1. Check equations for Total N Intake and Milk N. Typically feed uses a N correction factor of 6.25 and milk 6.38 (QUESTION 1). The model for Total N Excretion is missing key factors: N retained for animal requirements (maintenance, growth, reproduction) (QUESTION 2). Milk N should include both nitrogen from milk protein and MUN (QUESTION)
• Answer 1: It was a typo in the text, because milk N was calculated using a N correction factor of 6.38. N intake was corrected using N factor of 6.25.
• Answer 2. We used nitrogen milk N/N intake * 100 as indicator of nitrogen use efficiency. According to Correa-Luna et al. (2020) (DOI: https://doi.org/10.3390/ani10061036 ), all excess of N intake is excreted to environment with exception of a minor portion that would be retained by cows with positive energy balance. Each kg of BW change was assumed to contain 160 g of CP. Studies included in the database did not report body weight change. Additionally, cows in early and mid-lactation are in negative energy balance, therefore, they should have a low N retention. According to work carried out for a coauthor (Keim et al. 2021; DOI: https://doi.org/10.3168/jds.2021-20215), growth N for dairy cattle ranged 1.3-2.4% of N intake. Due to the lack of information (Change in body weight) and negative energy balance of cows, we assumed that N retention = 0. We have declared this information in the text (Line 169-177).

• Answer 3. Milk N urea is considered in the estimation of milk N, because CP content in milk (reported in studies include in this database) include all N compounds as part of their structure (true protein and non-protein N). We have included a new citation (published this year) to support our equation.

Table 3. Is this a count of articles that reported the variables? Only some of this information is shown in Figure 2. The authors can greatly improve the table by adding summary statistics of the variables used in model selection (e.g., a table that reports means, variation, number of observations, etc.).
• Answer. We agree referee that statistical summary of the variables used in model selection will improve the quality of study. We have included descriptive information in table 3 as suggested.

Table 5. Did the different systems, stage of lactation, or season affect milk N?
• Answer. Effect of system, stage of lactation and season on milk N was included in the table 5 and results/discussion. See Lines 324-332 and 350-358.

Figures 3 and 4. Statistical information must be added to the graphs. Was the intent correlation or regression?
• Answer. Marginal R2 and p values were included in figures 3 and 4.

Figure 3a, 3c. Is there any commonality if the outliers?
• Answer. There was not commonality between variables included in the full models. Multicollinearity was assessed by calculation of variance inflation factors (VIF) with variables having variance inflation factors greater than 5 removed from the models (Craney and Surles, 2002). A sentence was included in the text to clarify (Line 204-206)

 

Reviewer 2 Report

The authors compared nitrogen intake and partitioning for beef cattle and dairy cattle in Chile based on existing equations. Although the data size is not very large, the study is still meaningful for understanding the local livestock production system. Below are the detailed comments.

 

L68: “a small number of”. Same below.

 

L121: “Animal type” sounds like beef or dairy cattle. Maybe “animal characterization” would be better.

 

L122: Please explain “animal category” and “animal subcategory”.

 

Table 1: Eq. 7 should be NUE (%) = (TNI – TNE)/ TNI x 100%

 

L196: An extra parenthesis after “Table 2”.

 

L206: It seems to be a typo “between 27 and 27”.

 

Table 3: As mentioned above, there were 119 observations for dairy cattle and 28 observations for beef cattle. Then why are there 29 observations of total N intake for beef cattle? And why are there only 115 observations of NUE and dung N for dairy cattle?

 

Table 4: Given the unbalanced dataset (119 vs 28), the direct comparison between dairy and beef cattle could be dangerous. Besides, based on the excretion and intake of N for beef cattle, the NUE seems too high. Please double check if the numbers are correct.

 

L268: Seem to be a typo.

 

Table 5 and 6: Please keep consistent of the description of “System” by using the abbreviations you mentioned in the context (GS, GSS, CS).

 

Table 6: Again, the NUE values seem too high based on based on N excretion and intake.

 

Table 7: I am not sure how RMSE and CCC were calculated. Did the authors conduct a cross validation? Or the RMSE and CCC were calculated based on the fitted values? If it is the latter, then the result is a bit misleading, since the random effect of study cannot be used to predict for independent datasets.

 

Author Response

REVIEWER 2
Dear reviewer
We would like to thank for your comments and suggestions, which improved the quality of manuscript. As a result of this process, the original text has undergone modifications. We have attended all your comments, using track changes in Word. An answer for each comment was included, as described below.

Best regards
Ignacio Beltrán
Correspondence author

ANSWER TO REVIEWER 2
Comments and Suggestions for Authors
The authors compared nitrogen intake and partitioning for beef cattle and dairy cattle in Chile based on existing equations. Although the data size is not very large, the study is still meaningful for understanding the local livestock production system. Below are the detailed comments.
L68: “a small number of”. Same below.
• Answer. Text was edited as suggested by reviewer.
L121: “Animal type” sounds like beef or dairy cattle. Maybe “animal characterization” would be better.
• Answer. Text was edited as suggested by reviewer.
L122: Please explain “animal category” and “animal subcategory”.
• Answer. Text was edited as suggested by reviewer. See Line 138-139.
Table 1: Eq. 7 should be NUE (%) = (TNI – TNE)/ TNI x 100%
• Answer. Equation was edited as suggested by reviewer.
L196: An extra parenthesis after “Table 2”.
• Answer. Text was edited as suggested by reviewer.
L206: It seems to be a typo “between 27 and 27”.
• Answer. It was a typo. Text was edited.

Table 3: As mentioned above, there were 119 observations for dairy cattle and 28 observations for beef cattle. Then why are there 29 observations of total N intake for beef cattle? And why are there only 115 observations of NUE and dung N for dairy cattle?
• Answer 1. We really appreciate your revision. It was a mistake in the number of observations declared for NUE in dairy cattle (117 instead of 115). We used NUE to determine the number of observations in the database ((117 for dairy cattle and 28 for beef cattle = 145
• Answer 2. Then why are there 29 observations of total N intake for beef cattle? This sentence means that we found 29 observations for N intake, however, it was possible to estimate the NUE for 28 observations. A similar explanation for differences between total N intake and NUE for dairy cattle.

Table 4: Given the unbalanced dataset (119 vs 28), the direct comparison between dairy and beef cattle could be dangerous. Besides, based on the excretion and intake of N for beef cattle, the NUE seems too high. Please double check if the numbers are correct.
• Answer. Yes, we agree that dataset for dairy and beef cattle are unbalanced, however, we have declared the number of observations in the text, which should be considered by readers.
• Answer 2. Regarding high NUE for beef cattle, these values agree with information collated from Chilean studies. Additionally, the high NUE for beef cattle agree with the data collated, however, it was mistake in the transcription of N intake from Rstudio to Word, which was edited in Table 6. We appreciate your specific review.

L268: Seem to be a typo.
• Answer. We can´t find the typo suggested by reviewer

Table 5 and 6: Please keep consistent of the description of “System” by using the abbreviations you mentioned in the context (GS, GSS, CS).
• Answer. We have edited the text as suggested.

Table 6: Again, the NUE values seem too high based on based on N excretion and intake.
• Answer. We have edited the information for N intake, which was greater than reported in the table. The high NUE reported in the table is related to information found for Chilean studies.

Table 7: I am not sure how RMSE and CCC were calculated. Did the authors conduct a cross validation? Or the RMSE and CCC were calculated based on the fitted values? If it is the latter, then the result is a bit misleading, since the random effect of study cannot be used to predict for independent datasets.
• Answer. Indeed, CCC and RMSE values were calculated using the values observed in our database versus those predicted by the selected equations. Considering that our database has a small number of observations, it was not possible to perform a cross-validation. Therefore, we decided to remove the RMSE and CCC calculations to avoid confusion for readers.

 

Reviewer 3 Report

Reviewer General Comments

This paper brings together a database of data on nitrogen intake and its partition on urine, dung, and products of dairy and beef cattle in Chile. It is well researched, presented, and discussed. This paper is relevant to farmers, extensionists, and governmental authorities specifically in Chile however, the findings of the research are fully in agreement with previously published international research. I would encourage the author to make clearer what the hypothesis of this research was (what did you expect to observe in the data from Dairy and Beef cattle in Chile that would be different from other systems in temperate climates) and what new novel information this research found.

A more fitting title may be something like the following: ‘Nitrogen intake and its partition on urine, dung, and products of dairy and beef cattle in Chile’

The conclusion of the abstract is very general and states what we already know from the literature -N excretion varied according to the type of animal and production system, being greater for dairy compared to beef cattle. Please report what the key new findings of this research are or what this Chile-specific works add to existing knowledge.

The data is compared to two other data sets however, one is American and one is African. Comparisons for N values should be made with study’s carried out under similar environmental conditions/temperate climates.

All Tables and Figures must be checked for use of abbreviations and ensure footnotes are included to explain their meaning.

 

Reviewer Specific Comments

Line 3: What is meant by ‘on a temperate climate’ ?

A more fitting title may be something like the following: ‘Nitrogen intake and its partition on urine, dung and products of dairy and beef cattle in Chile’

The title could also incorporate the systems comparison – GS, GSS and CS

Line 14-15: throughout? Rephrase. Suggestion: Nitrogen that is excreted throughout the urine and dung of cattle is an important source of nitrous oxide and ammonia emissions.

Line 15: N – not previously abbreviated

Line 15-16: Wording could be improved. Suggestion: ‘ … N intake and their  its partitioning into urine and dung for from beef and dairy cattle, however, there are not no studies collating..’.

Line 17: Wording could be improved. Suggestion: ‘which would allow to estimate  an estimation of the N excretion and its key variables to be developed’.

Line 19: The aim of this study

Line 25-26: Abbreviations should be defined the first time they appear in each of three sections: the abstract; the main text; the first figure or table.

Line 27-28: The conclusion of the abstract is very general and states what we already know from the literature -N excretion varied according to the type of animal and production system, being greater for dairy compared to beef cattle. Please report what the key new findings of this research are.

Line 39: pasture not pastures

Line 40: CP – not previously abbreviated

Line 43: removed from the rumen

Line 45: exported should be excreted?

Line 46: main way vs the main pathway?

Line 47: Reword: .. ‘however, it is also being quickly volatilized as ammonia’

Line 50: ‘could contributed’

Line 55: ‘…are calculated by multiplying…’

Line 58: ‘…animal species,…’

Line 60-62: The aim of the introduction is to summarise the literature and set the context of your research objective.  Specific reference to the work of the paper should not be mentioned.

Suggested rewording: ‘and expert judgements. Country-specific data for different cattle and animal production systems (grazing or confined) could improve the estimation of total N excretion (urine plus dung) however, there is a paucity of such a database to collect this information’.

Line 67-68: It is well documented internationally that NUE and total N excretion varys between beef and dairy cattle. It would appear that the Chilean studies that have been conducted have reached the same conclusion. Please explain why you would expect Chilean dairy and beef cattle to deviate from this?

Line 72: from the literature

Line 77: or livestock from the developing countries

Line 78: ‘The development of local databases could also allow the identification of potential variables specific to each country..’

Line 83: nitrogen use efficiency (NUE) -  already abbreviated

Line 84: C cattle

Line 85: Please include a hypothesis

Line 114: ‘throughout spot of urine and dung’- spot sampling? Please clarify

Line 147: ‘A similar procedure’

Line 149: NUE in the title must be spelled out and N is not defined as nitrogen in this table - Abbreviations should be defined the first time they appear in each of three sections: the abstract; the main text; the first figure or table. Please check all abbreviations in all Tables.

Line 151: Please be consistent with punctuation - CP: Crude protein, DMI: Dry matter intake; ME: M

Line 154: ‘During this process, a different person that to whom entered the data into the database checked’

Line 157:Rewording: ‘the case of duplication, peer review publications were maintained in the database peer review publication instead of theses or conference papers’.

Line 175: ‘the selection of variables influencing the N’

Line 202: N – should be spelled out. Please check abbreviations throughout the manuscript

Line 206: ranged between 27 and 27 observations – Typo?

Line 208: was entered into the database.

Line 210: Each table should be able to be understood independently of the manuscript. Please include footnotes of the in-table abbreviations and their meanings.

Line 215: Why were values under 20% classes as extremes? The literature has reported lower NUE values as lactation progresses. Values of 18% have been reported for cows in mid-lactation and 11 to 12% for cows in late lactation. Please clarify.

Line 221-223: You compare your database values with two other databases one in the US and the other from Africa. As expected your values reflect the pasture-based systems and therefore deviate from the values in the other two data sets. I would suggest you make reference to how your database values compare to data from pasture bases systems such as those in New Zealand and Ireland which would be a fairer comparison.

Line 225: ‘Although urinary N excretion was greater than previous literature values’ – you are only referencing two other studies where the environmental conditions are not similar to Chile. Please rewrite this section to include more references from a similar temperate grazing climate.

Line 234: In Figure 3 the Y-axis is unlabelled. Please include what the term ‘count’ refers to. 

Line 268: 1 Tables may have a footer. What does this mean? Please see the comments above in relation to the abbreviations in Tables 1-3.

Line 278: ‘reported that the majority of urinary N is excreted as’

Line 301: Reword – ‘In our the current study,’

Line 305: ‘The described above aforementioned ’

Line 309: Please check all abbreviations in all Tables. Abbreviations should be defined the first time they appear in each of three sections: the abstract; the main text; the first figure or table.

Line 309: In Table 6 there is an extra internal line in the table above Summer which is not needed.

Line 337: in Figure 3 ADF should be spelled out and then abbreviated

Line 349: Milk urea Nitrogen (MUN)

Line 364: ‘However, it is evident that there are differences

Line 374: Figure 5a needs to be centered as it appears skewed to the right. The text also appears quite small and difficult to read

Line 380: ‘This is the first study collating data available in the literature on N partitioning of dairy and beef cattle in Chile.’ Please include some content as to why this dataset is important and why the existing data in the literature (which the work of this dataset agrees with) was insufficient. What is the novelty of this data set and manuscript?

Line 384: N use efficiency -NUE – Consistency with abbreviations is important

Line 387: ‘which allowed the identification to identify that N excretion was partially modified by animal category, system type and season of the year’.  This is already well-published in the literature. Why was it important to establish this specifically for Chilean production systems?

Line 389: the number of heads of in beef

Line 390: represents 66.5% of the total of Chilean cattle

Line 397: ‘metabolizable protein instead of CP system allows for a reduction in N intake, without differences on in average LWG

Line 404: working in with beef cattle

Author Response

REVIEWER 3
Dear reviewer
First of all, we really appreciate your thorough review in terms of grammar and information, which allowed to improve the quality of manuscript. We have attended all of your comments, using track changes in Word. An answer for each comment was included, as described below.

Best regards
Ignacio Beltrán
Correspondence author

ANSWERS TO REVIEWER 3
Reviewer General Comments
This paper brings together a database of data on nitrogen intake and its partition on urine, dung, and products of dairy and beef cattle in Chile. It is well researched, presented, and discussed. This paper is relevant to farmers, extensionists, and governmental authorities specifically in Chile however, the findings of the research are fully in agreement with previously published international research.
I would encourage the author to make clearer what the hypothesis of this research was (what did you expect to observe in the data from Dairy and Beef cattle in Chile that would be different from other systems in temperate climates) and what new novel information this research found.
A more fitting title may be something like the following: ‘Nitrogen intake and its partition on urine, dung, and products of dairy and beef cattle in Chile’
The conclusion of the abstract is very general and states what we already know from the literature -N excretion varied according to the type of animal and production system, being greater for dairy compared to beef cattle. Please report what the key new findings of this research are or what this Chile-specific works add to existing knowledge.
The data is compared to two other data sets however, one is American and one is African. Comparisons for N values should be made with study’s carried out under similar environmental conditions/temperate climates.
All Tables and Figures must be checked for use of abbreviations and ensure footnotes are included to explain their meaning.

Reviewer Specific Comments
Line 3: What is meant by ‘on a temperate climate’ ?
A more fitting title may be something like the following: ‘Nitrogen intake and its partition on urine, dung and products of dairy and beef cattle in Chile’
• Answer. We agree referee, therefore, Tittle was edited as suggested.

The title could also incorporate the systems comparison – GS, GSS and CS
• Answer. It is not possible to include systems in the tittle due to the limited number of words allowed. (max: 15 words)
Line 14-15: throughout? Rephrase. Suggestion: Nitrogen that is excreted throughout the urine and dung of cattle is an important source of nitrous oxide and ammonia emissions.
• Answer. It was edited as suggested.

Line 15: N – not previously abbreviated
• Answer. Abbreviation was included.

Line 15-16: Wording could be improved. Suggestion: ‘ … N intake and their its partitioning into urine and dung for from beef and dairy cattle, however, there are not no studies collating..’.
• Answer. Text was edited according to reviewer comments.

Line 17: Wording could be improved. Suggestion: ‘which would allow to estimate an estimation of the N excretion and its key variables to be developed’.
• Answer. Text was edited as suggested.

Line 19: The aim of this study
• Answer. Text was edited as suggested.

Line 25-26: Abbreviations should be defined the first time they appear in each of three sections: the abstract; the main text; the first figure or table.
• Answer. Text was edited as suggested.

Line 27-28: The conclusion of the abstract is very general and states what we already know from the literature -N excretion varied according to the type of animal and production system, being greater for dairy compared to beef cattle. Please report what the key new findings of this research are.
• Answer. we added the suggestion and changed the conclusion on Lines 29-33.

Line 39: pasture not pastures
• Answer. Text was edited as suggested.

Line 40: CP – not previously abbreviated
• Answer. Text was edited as suggested.

Line 43: removed from the rumen
• Answer. Text was edited as suggested.

Line 45: exported should be excreted?
• Answer. Text was edited as suggested.

Line 46: main way vs the main pathway?
• Answer. We have modified the text to “main pathway”
•

Line 47: Reword: .. ‘however, it is also being quickly volatilized as ammonia’
• Answer. Text was edited as suggested.

Line 50: ‘could contributed’
• Answer. Text was edited as suggested.

Line 55: ‘…are calculated by multiplying…’
• Answer. Text was edited as suggested

Line 58: ‘…animal species,…’
• Answer. Text was edited as suggested

Line 60-62: The aim of the introduction is to summarise the literature and set the context of your research objective. Specific reference to the work of the paper should not be mentioned.
Suggested rewording: ‘and expert judgements. Country-specific data for different cattle and animal production systems (grazing or confined) could improve the estimation of total N excretion (urine plus dung) however, there is a paucity of such a database to collect this information’.
• Answer. We really appreciate your comments and editions. Text was edited as suggested.

Line 67-68: It is well documented internationally that NUE and total N excretion varys between beef and dairy cattle. It would appear that the Chilean studies that have been conducted have reached the same conclusion. Please explain why you would expect Chilean dairy and beef cattle to deviate from this?

• Answer. We have added a short sentence on Line 77-79. Additionally, we have added a full paragraph explaining what we are expecting on N partitioning in dairy and beef cattle by a new database (Line 88-95)

Line 72: from the literature
• Answer. Text was edited as suggested

Line 77: or livestock from the developing countries
• Answer. Text was edited as suggested

Line 78: ‘The development of local databases could also allow the identification of potential variables specific to each country..’
• Answer. Text was edited as suggested

Line 83: nitrogen use efficiency (NUE) - already abbreviated
• Answer. Text was edited as suggested

Line 84: C cattle
• Answer. Text was edited as suggested

Line 85: Please include a hypothesis
• Answer. We have included a hypothesis as suggested. Line 93-98.

Line 114: ‘throughout spot of urine and dung’- spot sampling? Please clarify
• Answer. Interpretation of reviewer is correct. We have edited the text to “spot sampling of urine and dung”. Check Line 165-169.

Line 147: ‘A similar procedure’
• Answer. Text was edited as suggested

Line 149: NUE in the title must be spelled out and N is not defined as nitrogen in this table - Abbreviations should be defined the first time they appear in each of three sections: the abstract; the main text; the first figure or table. Please check all abbreviations in all Tables.
• Answer. We have checked and edited all abbreviations in tables.

Line 151: Please be consistent with punctuation - CP: Crude protein, DMI: Dry matter intake; ME: M
• Answer. Text was edited as suggested

Line 154: ‘During this process, a different person that to whom entered the data into the database checked’
• Answer. Text was edited as suggested

Line 157:Rewording: ‘the case of duplication, peer review publications were maintained in the database peer review publication instead of theses or conference papers’.
• Answer. Text was edited as suggested

Line 175: ‘the selection of variables influencing the N’
• Answer. Text was edited as suggested

Line 202: N – should be spelled out. Please check abbreviations throughout the manuscript
• Answer. It was edited as suggested. Abbreviation of manuscript were checked

Line 206: ranged between 27 and 27 observations – Typo?
• Answer. It was a typo, thank you. Text was edited as suggested.

Line 208: was entered into the database.
• Answer. Text was edited as suggested

Line 210: Each table should be able to be understood independently of the manuscript. Please include footnotes of the in-table abbreviations and their meanings.
• Answer. Tables were edited as suggested.

Line 215: Why were values under 20% classes as extremes? The literature has reported lower NUE values as lactation progresses. Values of 18% have been reported for cows in mid-lactation and 11 to 12% for cows in late lactation. Please clarify.
• Answer. We agree reviewer that literature report NUE values under 20%. However, our sentence is related to the range of data according to confidence interval (95%), which suggests that values under 20% were considered as extreme for the current database.

Line 221-223: You compare your database values with two other databases one in the US and the other from Africa. As expected, your values reflect the pasture-based systems and therefore deviate from the values in the other two data sets. I would suggest you make reference to how your database values compare to data from pasture bases systems such as those in New Zealand and Ireland which would be a fairer comparison.
• Answer. We have included results from studies and database carried out in New Zealand. See Lines 271-280 and 325-332.

Line 225: ‘Although urinary N excretion was greater than previous literature values’ – you are only referencing two other studies where the environmental conditions are not similar to Chile. Please rewrite this section to include more references from a similar temperate grazing climate.
• Answer. We found a New Zealand database for dairy cattle (pasture-based systems), which was included in discussion section as suggested. Line 324-332.

Line 234: In Figure 3 the Y-axis is unlabelled. Please include what the term ‘count’ refers to.
• Answer. It was included a sentence “Count = Number of observations “. Check Line 290.

Line 268: 1 Tables may have a footer. What does this mean? Please see the comments above in relation to the abbreviations in Tables 1-3.
• Answer. We forgot to remove the text from original template of journal. Text was removed.

Line 278: ‘reported that the majority of urinary N is excreted as’
• Answer. Text was edited as suggested

Line 301: Reword – ‘In our the current study,’
• Answer. Text was edited as suggested

Line 305: ‘The described above aforementioned ’
• Answer. Text was edited as suggested

Line 309: Please check all abbreviations in all Tables. Abbreviations should be defined the first time they appear in each of three sections: the abstract; the main text; the first figure or table.
• Answer. Tables were edited as suggested.

Line 309: In Table 6 there is an extra internal line in the table above Summer which is not needed.
• Answer. Table was edited as suggested

Line 337: in Figure 3 ADF should be spelled out and then abbreviated
• Answer. Figure was edited as suggested

Line 349: Milk urea Nitrogen (MUN)
• Answer. Text was edited as suggested

Line 364: ‘However, it is evident that there are differences
• Answer. Text was edited as suggested

Line 374: Figure 5a needs to be centered as it appears skewed to the right. The text also appears quite small and difficult to read
• Answer. Figure was modified as suggested.

Line 380: ‘This is the first study collating data available in the literature on N partitioning of dairy and beef cattle in Chile.’ Please include some content as to why this dataset is important and why the existing data in the literature (which the work of this dataset agrees with) was insufficient. What is the novelty of this data set and manuscript?
• Answer. We have added a sentence in the text as suggested. Line 458-463.

Line 384: N use efficiency -NUE – Consistency with abbreviations is important
• Answer. Text was edited as suggested

Line 387: ‘which allowed the identification to identify that N excretion was partially modified by animal category, system type and season of the year’. This is already well-published in the literature. Why was it important to establish this specifically for Chilean production systems?
• Answer. The information reported in this study can contribute to a more accurate estimation of the national GHG Inventory. We have included a sentence in the text. Please, check Line 466-469.

Line 389: the number of heads of in beef
• Answer. Text was edited as suggested

Line 390: represents 66.5% of the total of Chilean cattle
• Answer. Text was edited as suggested

Line 397: ‘metabolizable protein instead of CP system allows for a reduction in N intake, without differences on in average LWG
• Answer. Text was edited as suggested

Line 404: working in with beef cattle
• Answer. Text was edited as suggested

Round 2

Reviewer 1 Report

The authors have addressed the major concerns with scientific soundness in the revised manuscript.