Estimation of Energy Value and Digestibility and Prediction Equations for Sheep Fed with Diets Containing Leymus chinensis Hay
Round 1
Reviewer 1 Report
The work presented in this manuscript is very interesting and relevant as it shows the bromatological composition of sheepgrass of several regions from China and its value as to feed cattle. The work is simple and similar studies have been reported previously in this regard. However, the work is scientifically well. These are my specific comments:
-The English presentation and style of the manuscript should be improved significantly. This is the most important concern I have with this manuscript.
. Line 38. In which area?
-Line 57. …on its nutrition? Perhaps, nutritional value.
-It is hard to understand lines 82-83.
-Line 87. What ripening stage is? Could you provide the physiological indicators of sheepgrass used to determine the harvest date?
-Line 147. I suggest using an impersonal style of writing.
-line 210. It should be Table 4.
-It is hard to understand line 228..
-Figures 3 and 4. The titles of the axis are not visible.
-in my opinion, 5 animals per treatment was insufficient.
-The authors argue that the chemical composition of sheepgrass varied significantly, however, data of Table 3 show the opposite.
-I missed the quantification of other important components in sheepgrass (e.g., carotenoids), which can alter the metabolism of cattle.
My main concern on this manuscript is its English presentation. The style should also improved.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Editor
All opinion was emitted with all respect to the efforts of the authors for the preparation of the experiment and its report
General
The purpose of this study was to estimate the energy value and expected DMI of diets containing 28% of Sheepgrass hay through digestibility coefficients determined in vivo. Even though this reviewer acknowledges the hard work devoted by the authors to the present experience, I also consider that the manuscript, as it is presented, has flaws that limit its consideration for publication in Agriculture Journal. As is presented no novelty is appreciated. Materials and methods need to be improved in it description. Results must be rearranging. Discussion is vague and not focused in the main.
Here the arguments
The main concern is how the Material and Methods are exposed and the manner which data are presented.
1) In this type of experiment, a replacement technique is usually utilized to determine the energy value of feedstuffs. For that, a reference ingredient is needed. The attributes (or requirements) that a reference ingredient must accomplish is that its energy value is well known. For example, to determine energy value of cereals, corn grain is the main reference ingredient, for grasses (hay), could be sudangrass hay, ryegrass hay. The energy value of these ingredients are published in current standards (NASEM, ARC, among others). In this case, the reference ingredient was Millet grass silage. Known the energy value of millet grass silage the energy of tested ingredient can be estimated as follows (assuming that DE value of millet silage is 2.60 Mcal/kg, this as example):
DE of SG, Mcal/kg = [(DE test diet-DE reference diet)/0.285] + 2.60] x 4.184
where DE is expressed in Mcal/kg, 0.285 is participation level of SG that replace millet, 2.60 is the energy value of millet and 4.184 the factor to convert to MJ.
However, authors did not indicate the energy value of the millet grass silage used to determine the energy value of sheepgrass hay (SG).
2) It is recommended that Tables be presented with the average data (of the 10 samples) of the chemical composition of reference forage (millet silage) and forage tested (sheepgrass hay) which is missing (could be Table 1). In the same manner, a Table with intakes, fecal excretion, digestion coefficients and their energetic value (average two experiments). This is valuable for the livestock feed industry (Hint).
Table 2. Influence of sheepgrass hay on characteristics of total tract digestion and its estimated energy value1
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Treatments a |
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Millet silage |
Sheepgrass |
SEM |
P value |
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Intake (g/d) |
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DM |
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OM |
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NDF |
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CP |
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EE |
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Gross energy (Mcal/kg) |
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Fecal excretion (g/d) |
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DM |
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OM |
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NDF |
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CP |
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EE |
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Gross energy (Mcal/kg) |
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Total tract digestion (%) |
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DM |
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OM |
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NDF |
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CP |
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EE |
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Diet DE (Mcal/kg) |
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Diet ME (Mcal/kg) |
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Sheepgrass hay DE (Mcal/kg) |
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XX |
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Sheepgrass hay ME (Mcal/kg) |
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XX |
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1Average of 10 samples (two digestion experiments) from different sites at similar stage of maturity
And then, discussion must be related to the energy value determined
Specific
Title
Due to the nature of the experiment more proper title is: Estimation the energy value and prediction equations through digestibility coefficients in sheep fed with diets containing Leymus chinensis hay
Abstract
Must be improved
L16: please use “feeding value” instead “nutritional value”
L20: Two independent experiment under a completely randomized experimental design were performed in order to evaluate…
What was the average metabolizable energy determined to sheepgrass?
It is well known that chemical composition can explain DMI and digestibility. In the case of diets contained up to 28.5% of sheepgrass is accordingly to the other equations development for sheep with other forage hay sources??
Conclusion is very simple, does not say nothing new!! Readers expect something such as: The energy value of sheepgrass correspond to 0.80 of the energy value of millet silage. The main component that affect DMI is XX, but the main component that affect digestibility is xxx. Shepgrass is a good forage source for sheep when it is included up to 28.5% in total mixed diets. Please focus your results and discussion in this conclusions!
Material and Methods
As is described is very confuse. Need to improve
L98: Avoid start the sentence with “In the present study” this is leftover. Basal diets? Accordingly, to Table 2, there is a one “basal diet” which in this case the proper term is “Reference diet” How do you estimated ME from sheepgrass diet (SG)? You need the ME of SG, Please, cite the reference where ME of sheepgrass was obtained.
L100-101: Which were the six treatments?? In line with the objective of the study, there are two diets, a reference diet using Millet grass silage as 'reference ingredient" and a "Test diet" in which Millet grass silage was partially replaced with sheepgrass (test ingredient). Due to the fact that 10 different sheepgrass samples were evaluated, it is understandable that the trial was completed in two consecutive experimental runs (5 reps/sample plus reference diet). In any case, there were 11 treatments (a reference diet plus 10 samples of sheepgrass), but as is described in the manuscript is very easy to confuse the readers. Please rewording in order to be more clear to the readers
Table 1. More useful and necessary, that Table 1 be presented with the average data (of the 10 samples) of the chemical composition of reference forage (millet silage) and forage tested (sheepgrass hay), instead that regions in which samples were obtained.
Table 2. Include chemical composition of diets (as an average from 10 samples of SG).
Statistical analyses
Please specify the follow: All data were analyzed as two independent experiment under a completely randomized experimental design were performed.
Results
Almost all results obtained here regarding correlation, are expected. Please, take in account this when expose the results.
L210: Digestibility and energy value are presented in Table 3?? Correct it.
Discussion
It is necessary that results (energy value, digestibility, and prediction equations) are contrasted and discussed comparing current standards or previous reports. This is not the case. Discussion must be focused and improved in this way
L252: Start the sentence: “As is expected a significant correlation…
Table 3. Chemical composition of reference ingredient is missing. Please include it as is suggested previously. A footnote clarification “origin of corn” are described in Table 1. Why corn?????
Table 8. Be careful! The prediction equation for DMI is not for sheepgrass, it is for a total mixed diet containing 28.5% of sheepgrass. This results must be contrasted with the current standard or with previous equations reported to sheep feeding total mixed rations containing moderate energy.
Too many equations! Please, expose the best equation (maybe two) for each parameter. Several equations are unnecessary to be exposed.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
The study investigated the nutritional value of sheepgrass, including its chemical composition, dry matter intake, nutrient digestibility, and available energy, while establishing the prediction equations of dry matter intake (DMI), neutral detergent fiber digestibility (NDFD), dry matter digestibility (DMD), digestive energy (DE) and metabolic energy (ME). The manuscript falls within the scope of the journal and can be accepted after revision.
(1) The main problem with the experiment is the low number of animals in each treatment. 5 animals in each treatment are low to extract the best-fit equations.
(2) Many grammatical mistakes were observed.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
My main concern with this work was the English/style presentation. The authors have gotten assistance in this regard.
Reviewer 2 Report
I have read the revised manuscript and appreciate the authors' consideration of my previous suggestions. All of my observations have been covered in an acceptable manner, in such a way that I have no further observations.
