Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The work presents information that may be of practical significance for cat food formulation. The background, methods and results are clearly presented and appropriately contextualized. The inclusion of the analytical chemistry data is much appreciated and essential.  My primary concern is the absence of data for the one concentration of olive extract tested previously with no adverse effect (1,000ppm), reference 10. Additionally, it is unclear how the doses tested relate to those found to have any type of functional physiological effect. This is critical information for the reader to assess the significance of the study. Further, the data provided, as ppm, and solely as intake ratio with no information on amount consumed makes it impossible for the reader to even attempt to extrapolate from data in other animals where, for instance, doses of 25 mg/kg of hydroxytyrosol in an olive extract have been reported to have anti-inflammatory effects in mice (e.g., see doi: 10.3390/nu17020223 and references contained therein). 

Minor edits: 

• Section 2.3 Intake Ration (IR) should be Intake Ratio
• Please indicate number of males/females
• If possible to identify oleocanthal and related compounds that would assist the reader in understanding how to compare this material with other sources - this is among the key anti-inflammatory compounds in olive oil and extracts and also is likely to have unpleasant sensory attributes (see e.g., https://pmc.ncbi.nlm.nih.gov/articles/PMC4139846/ for review and references therein and https://pmc.ncbi.nlm.nih.gov/articles/PMC4357805/ on sensory properties). It would be helpful to note whether the concentrations used elicited throat irritation. The mode of administration would likely minimize direct exposure to the oral cavity and throat but the palatant may mask that and it would be helpful to know. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper examines Feline Responses to Increasing Inclusion of Natural Olive Extract in Liquid or Dry Palatant Formulations Applied to Kibble Diets, and the study has implications for the effects of adding OE to cat food on the The study has some value for adding OE to cat food for palatability. However, the article has the following comments for the authors to make recommendations:

1. In the Abstract, Line 21-23, the IR of OE was not significantly different from that of the control group, but in Figure 3, the IR of the 200 ppm group was significantly higher than that of the control group, and the difference here should not be ignored.
2. Line 49-50, “In addition to catnip, anecdotal reports suggest that cats readily consume olives which may be offered in small amounts as treats in homes or veterinary clinics.” Is there a reference here to support this, please add it.
3. Please add the extraction process and purity of OE in the Materials and Methods section.
4. Please add the composition and nutritional level of the test cat food.
5. The number of cats in this trial was 20, but it was not clearly stated whether the 20 cats were randomly assigned to different groups or whether there were 20 cats in each group, so please provide a clearer description of the number of test animals.
6. The authors are requested to provide additional information on the health status of the cats and the environmental conditions, such as temperature, humidity, caged or free-ranging, and the size of the housing area, which is essential for animal welfare.
7. This experiment was conducted on animals for only 2 days. According to the principle of palatability test design, the test period should be a multiple of 2, but the shortest time of 2 days was used in this experimental design, and we are skeptical about the reliability of the results of this short experimental design. If possible, it is recommended to extend the test period.
8. OE is added to cat food in two forms: liquid and solid, and the amount of OE added to cat food in these two forms is different, so the authors are requested to explain the basis for the different amounts of OE added.
9. It is recommended that information on the daily intake of cats be provided.
10. Comparisons between different OE-added groups and the Control group were made in the article, and the comparisons between different OE-added groups and between liquid and solid forms of OE-addition are also of great significance for the application of OE in cat food, so it is suggested that the authors conduct additional analysis.
11. Fecal quality, nutrient digestion and metabolism, and the presence or absence of other nutritional functions of OE during the period of OE addition may be of even greater value for the use of OE as an additive in cat diets, and the authors are invited to make additional considerations.

Comments on the Quality of English Language

The author is advised to check the grammar of the manuscript and revise it.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

A very well written up study, thank you - some comments and questioning of possible 'over interpretation' at this stage: - see detailed annotations in the attached file.

 Methods could be made a little clearer as to test protocol and possibly aims/objectives - was there a time limit or did cats consume whole diet? etc..  Results and discussion useful together - but needs to expand or be more critical at times. - the interpretation that the first choice and first approach differ so consistently between the days hints towards something else than 'sidedness' as you said you alternated sides - please explore more (could have been tested for?)-- Also could assess if OE first approached then how many times was it also first choice?

  In particular would like to see if there is a difference in IR between day one and two in a similar manner??    in which case the study does not show a clear acceptability of the OE - as the averages are misleading and on day 3 it may be even worse, if you had done 3 days - which would normally be standard procedure -however as cats got multiple (much more than 3 days of the diet) the change between day's 1 and 2 on all treatments needs to be explored more...

Can be more critical in final discussion and conclusion stating that this is a promising pilot study and long term acceptance and health effects need to be researched further. or provide evidence for this if it exists already? 

Editorial/scientific style

Some improvement on figures is possible - clarification -only one title (Figure X..) would be below not above... but maybe style of this journal...  in my mind giving the p-value when  not sig. is not necessary and stating ns every time also - if you indicate significance already; 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The reviewer thanks the authors for considering all comments and the revised manuscript addresses all concerns thoroughly and appropriately.

A minor correction, on line 269 there is an erroneous 'was' inserted or left over.

Author Response

This version was corrected to address a typographical error noted by Review 1. 

Reviewer 2 Report

Comments and Suggestions for Authors

The authors provide clear answers to the questions posed. The experimental methods are clearly stated and the results are reasonable. The limitations of the article and future research interests are also clearly stated. The content of this study has practical applications for the use of olive extract in cat diets.

Comments on the Quality of English Language

The language of the manuscript allows for a clearer description.

Author Response

This version was corrected to address a typographical error noted by Review 1. 

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for your amendments which I think make this overall a much stronger paper and point towards the need for further research.

Author Response

This version was corrected to address a typographical error noted by Review 1.