Review Reports - Effect of Dietary Supplementation with Rumen-Protected GABA (γ-Aminobutyric Acid) on Milk Productivity and Blood Profiles of Dairy Cattle Under Heat Stress Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This article presented a set of meaningful data from an animal trial. This reviewer’s suggestions are:

It will be better if the bodyweight and daily feed given are presented.

Lines 4, 14: Change ….”in” heat-stress… to “under” heat-stress…

Lines 89-91: Delete this sentence. It is redundant.

Line 93: The “(TMR, Table 1)” should be “(TMR, Table 2)”.

In Table 2: 27.5% water was added to the diet, how could the moisture be only 11.44%?

Line 128: “jugular vein of tail”? jugular vein is in the neck. If a vein in the tail, it cannot be jugular vein.

Line 133: add “and” before “stored”.

Line 134: add analysis after “cortisol”.

Line 142: Change “recording behavior…” to “which recorded behavior…”.

Line 210: delete “of treatments”

Lines 242, 263: delete “(HS)”. This abbreviation was used nowhere in the article

Line 271: change “evaluate” to “is evaluated”; “which calculated” to “which is calculated”.

Line 272: change “was classified” to “is classified”

Lines 273-274: change ”Generally, in Holstein cow, THI threshold was reported that THI 72 as starting point by decreasing productivity of Holstein cows [13].” to “Generally, THI 72 is set as a threshold since the productivity of Holstein cows starts to decrease [13].

Line 275: delete “Detailly,”

Line 278: change “identifies” to “identified”

Line 279: change “0 week to 6 week” to “week 0 to week 6”

Comments on the Quality of English Language

English Language needs improved.

Author Response

This article presented a set of meaningful data from an animal trial. This reviewer’s suggestions are:

It will be better if the bodyweight and daily feed given are presented.

Answer: Feed residue was not measured during the experimental period. Although we could not evaluate feed intake for each animal due to the absence of individual feeding gates, each treatment group was fed the same amount of feed, and no residue occurred.

Added “each cow was restricted to 21.26 kg DM/day to maintain consistent feed intake across treatments.” In line 93-94

Lines 4, 14: Change ….”in” heat-stress… to “under” heat-stress…

Answer: changed in to under in line 4.

Lines 89-91: Delete this sentence. It is redundant.

Answer: Deleted

Line 93: The “(TMR, Table 1)” should be “(TMR, Table 2)”.

Answer: Changed

In Table 2: 27.5% water was added to the diet, how could the moisture be only 11.44%?

Answer: That's a mistake. Change chemical composition data in Table 2.

Chemical composition¹
	Before	Change
Dry matter (%)	21.26	65.0
Moisture (%)	11.44	35.0
Crude protein (%DM)	3.11	14.6
Crude fiber (%DM)	5.28	24.8
NDF (%DM)	10.58	49.8
ADF (%DM)	6.81	32.0
Ca (%DM)	None	0.9
P (%DM)	None	0.6
TDN¹	14.47	68.1

Line 128: “jugular vein of tail”? jugular vein is in the neck. If a vein in the tail, it cannot be jugular vein.

Answer: Changed tail to neck. We have conducted that a blood sample was collected from the cow’s neck. In line 158

Line 133: add “and” before “stored”.

Answer: added

Line 134: add analysis after “cortisol”.

Answer: added

Line 142: Change “recording behavior…” to “which recorded behavior…”.

Answer: changed.

Line 210: delete “of treatments”

Answer: deleted.

Lines 242, 263: delete “(HS)”. This abbreviation was used nowhere in the article

Answer: deleted.

Line 271: change “evaluate” to “is evaluated”; “which calculated” to “which is calculated”.

Answer: Changed

Line 272: change “was classified” to “is classified”

Answer: Changed

Answer: Changed in line 306 to 309

Line 275: delete “Detailly,”

Answer: Deleted

Line 278: change “identifies” to “identified”

Answer: Changed

Line 279: change “0 week to 6 week” to “week 0 to week 6”

Answer: Changed

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

General Comment: The research in title “: "Effect of dietary supplementation with rumen-protected GABA (γ-aminobutyric acid) on the milk productivity and blood profiles of dairy cattle in heat-stress conditions" addresses a highly relevant and significant issue in dairy science—mitigating heat stress. The use of rumen-protected GABA is a novel approach that merits investigation. However, the protocol's validity and the clarity of its hypotheses and methodological details require substantial strengthening to support its claims convincingly.

Abstract

1- The research title mentions "heat-stress conditions." But abstract did not mention any detail about the temperature and humidity average during the experimental period. Besides, the authors did not clear the Temperature-Humidity Index value. So please state the temperature and humidity average and the specific THI threshold used to define the onset of heat stress.

Introduction

2- The introduction should more clearly delineate the specific physiological consequences of heat stress in dairy cattle such as altered endocrine status, oxidative stress, energy balance and feed intake etc. Please provide a more focused summary.
3- What is the proposed mechanism of action for GABA in ruminants? Since GABA is a neurotransmitter, how does peripheral supplementation purportedly influence metabolism or stress pathways? Is there evidence for GABA receptors in bovine tissues relevant to productivity (e.g., the hypothalamus-pituitary-adrenal axis, pancreas, or mammary gland)?
4- The rationale for using a rumen-protected form is critical. Is there evidence that dietary GABA is extensively degraded by rumen microbiota? Please cite preliminary data or literature supporting the need for rumen protection.
5- Please state the formal research hypotheses (H0 and H1) clearly at the end of the introduction.

Materials and Methods

6- This study comprehensively evaluates the effects of rumen-protected GABA on milk yield under heat stress. Given the well-established correlation between depressed feed intake and reduced milk synthesis in heat-stressed ruminants, did the authors collect and analyze feed intake data? Clarifying whether the observed benefits on milk yield were mediated through the mitigation of the feed intake reduction.

7- Were respiration rate and panting score quantified? These parameters are critical for corroborating rectal temperature data in confirming the physiological state of heat stress.

Discussion

8- GABA supplementation may be acting via a central (neural) effect to reduce stress perception or a peripheral effect on metabolism, authors should discuss this point.

Conclusion

9- Based on the results, what will be the specific, actionable recommendation for the dairy industry? Will it be a firm recommendation or a call for more research in specific areas (e.g., dose-response studies, long-term effects)?

Comments for author File: Comments.pdf

Author Response

We thank the reviewer for their thoughtful comments and suggestions.

Abstract

Answer: added sentence that “The temperature-humidity index (THI) is a numerical value that combines air temperature and relative humidity to assess the level of thermal stress or heat stress experienced by animals or humans. Generally, THI 72 is set as a threshold since the productivity of Holstein cows starts to decrease.” In line 28 to 32.

Introduction

The introduction has been revised overall.

Answer: added sentence that “In response to heat stress, animals activate both physiological and behavioral heat dissipation mechanisms. Dermal arteriole dilation redirects blood flow to the skin surface to promote heat exchange with the environment, while increased sweating and mouth breathing enhance evaporative cooling [3,4]. Concurrently, behavioral adjustments including shade-seeking and reduced activity help minimize metabolic heat generation and support thermoregulation” in line 61 to 65

3- What is the proposed mechanism of action for GABA in ruminants? Since GABA is a neurotransmitter, how does peripheral supplementation purportedly influence metabolism or stress pathways? Is there evidence for GABA receptors in bovine tissues relevant to productivity (e.g., the hypothalamus-pituitary-adrenal axis, pancreas, or mammary gland)?

Answer: added sentence that “Nutritionally, GABA is catabolized by mitochondrial GABA transaminase (GABA-T) to form succinic semialdehyde, which is subsequently oxidized to succinate and incorporated into the tricarboxylic acid (TCA) cycle, thereby contributing to cellular energy production” in line 86-89.

4- The rationale for using a rumen-protected form is critical. Is there evidence that dietary GABA is extensively degraded by rumen microbiota? Please cite preliminary data or literature supporting the need for rumen protection.

Answer: added sentence that “The rumen serves as a fermentation vat where microbial metabolism generates considerable metabolic heat. During heat stress, ruminants reduce feed intake to minimize the thermogenic effect of digestion and lower overall body heat production [8]. This decrease in feed intake is one of the primary factors contributing to the decline in milk production in dairy cows.” In line 71 to 75.

And

Added sentence that “Rumen temperature typically exceeds rectal temperature under normal feeding conditions due to heat generated by microbial fermentation [9]. Therefore, feeding nutrients with rumen undegradable characteristics can sustain nutrient intake while minimizing increases in core body temperature.” In line 75 to 78.

5- Please state the formal research hypotheses (H0 and H1) clearly at the end of the introduction.

Answer: added sentence that “Consequently, the provision of ruminally protected GABA may mitigate heat stress-induced decrements in productive performance, despite the paucity of research addressing this hypothesis.” In line 94 to 96.

Materials and Methods

Added “each cow was restricted to 21.26 kg DM/day to maintain consistent feed intake across treatments.” In line 122 to 123

7- Were respiration rate and panting score quantified? These parameters are critical for corroborating rectal temperature data in confirming the physiological state of heat stress.

Answer: Respiratory rate was not measured during the study period. Although rectal temperature was assessed, no significant differences were observed among treatment groups. Given that the thermal conditions in this study were not expected to induce substantial physiological changes sufficient to alter core body temperature, these data are not presented.

Discussion

8- GABA supplementation may be acting via a central (neural) effect to reduce stress perception or a peripheral effect on metabolism, authors should discuss this point.

Answer:

Thank you for their thoughtful comments and suggestions.

This study investigated the nutritional benefits of GABA supplementation for enhancing productivity during heat stress. Although GABA supplementation is recognized to exert multiple effects on the peripheral nervous system, the absence of appropriate biomarkers to assess these mechanisms precluded their evaluation in this study; therefore, these aspects were not included in the discussion.

Conclusion

Answer: added sentence “This study suggests that daily supplementation with 3 g of ruminally protected GABA may attenuate productivity decline in dairy cows during heat stress. Consequently, ruminally protected GABA represents a practical nutritional intervention for minimizing productivity losses in Holstein cows during periods of elevated ambient temperature.” In line 386 to 390.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript evaluates the effect of rumen-protected γ-aminobutyric acid (GABA) on milk production, milk composition, blood metabolites, and behavior in Holstein cows exposed to summer heat stress. The study is relevant, however, several methodological and statistical issues limit the interpretability of the findings, particularly the suitability of the statistical model and the accuracy of the diet composition data.

The overall hypothesis is reasonable, but it is not clearly stated in the Introduction. A more explicit explanation of why the selected GABA doses (3 and 6 g/d) were chosen would strengthen the rationale.

Cow selection criteria are not described. It is unclear whether animals were blocked or randomized within parity, milk yield, or DIM categories, which matters given the small sample size.

The statistical model as described is not appropriate for repeated weekly measurements on the same cows. Cow should be included as a random effect, and week should be modeled as a repeated factor with an appropriate covariance structure. Because of this simplified model, treatment p-values and tendencies may not be reliable, which affects the interpretation of results and should be addressed before drawing firm conclusions.

Simple Summary

The summary reads as a technical abstract. Please simplify the terminology and remove all statistical notation, focusing on the practical implications.

Abstract

The Abstract lacks methodological details. Specific farm coordinates and full date ranges may be unnecessary; this space would be better used to strengthen the description of the design. The statistical analysis (mixed model, repeated measurements) is not mentioned, and behavior and blood outcomes are omitted despite being central to the study.

Line 32: The tendency for milk yield should include the corresponding p-value.

Materials and Methods
Line 79: The criteria for selecting cows (DIM range, parity, baseline production, health status) are not described. Given the small sample size, this information is essential for evaluating the comparability of groups.

Table 2: The chemical composition values appear incorrect: CP, NDF, and ADF are far too low for a dairy TMR and do not reflect commonly observed nutrient ranges. Please verify and correct.

Milk composition
Clarify whether milk samples were composited across AM and PM milkings or analyzed separately and averaged.

Line 128: The phrase “jugular vein of tail” is incorrect. Please specify whether samples were collected from the jugular vein or the coccygeal vein.

Line 148: The current model does not include cow as a random effect or week as a repeated factor. For repeated weekly measurements, this is necessary to avoid pseudoreplication. As written, treatment effects may be underestimated in terms of uncertainty, which affects all primary outcomes. So I stopped my review here until clarification.

Results – Tables
Multiple tables labeled “Table 4”.

Author Response

Cow selection criteria are not described. It is unclear whether animals were blocked or randomized within parity, milk yield, or DIM categories, which matters given the small sample size.

Answer: Classification information for animals is presented in Table 1.

We designed the experiment to statistically increase the uniformity of the experimental units by setting the average number of days of lactation, milk flow, and parity of animals to be similar.

After verifying the random effects attributable to individual animal variation, no significant block effects were detected; consequently, statistical analysis was conducted using a completely randomized design (CRD).

Answer: After verifying the random effects attributable to individual animal variation, no significant block effects were detected; consequently, statistical analysis was conducted using a completely randomized design (CRD).

And

The sentence that “Statistical significance was compared between control and GABA treatment groups using the PDIFF option” was wrong. It was mistake.

So changed sentence as “Statistical significance was compared between the control and GABA treatment groups using the method of repeated measurement.” In line 174.

The objective of this study was to evaluate the effects of GABA treatment independent of temporal variation. Repeated measures analysis was employed, and results are presented on the independence of time and treatment effects, with no significant interaction detected between treatment and time effects. And, we presented in each table that there was no interaction between treatment group and time.

Simple Summary

The summary reads as a technical abstract. Please simplify the terminology and remove all statistical notation, focusing on the practical implications.

Abstract

Added sentence that “as a completely randomized design. Statistical significance was compared between the control and GABA treatment groups using the method of repeated measurement.” In line 35 to 37.

And added sentence that “). Blood metabolic profiles and cortisol did not differ significantly between the control and GABA supplementation groups. Activities in the GABA supplementation groups were significantly greater than those in the control group (p < 0.05). GABA supplementation groups of Rest and rumination were significantly lower than those in the control group (p <0.05).” in line 41 to 45.

Line 32: The tendency for milk yield should include the corresponding p-value.

Added in line 38.

Materials and Methods
Line 79: The criteria for selecting cows (DIM range, parity, baseline production, health status) are not described. Given the small sample size, this information is essential for evaluating the comparability of groups.

Answer: Classification information for animals is presented in Table 1.

We designed the experiment to statistically increase the uniformity of the experimental units by setting the average number of days of lactation, milk flow, and parity of animals to be similar.

Table 2: The chemical composition values appear incorrect: CP, NDF, and ADF are far too low for a dairy TMR and do not reflect commonly observed nutrient ranges. Please verify and correct.

Answer It is mistake. Corrected in Table 2.

Milk composition
Clarify whether milk samples were composited across AM and PM milkings or analyzed separately and averaged.

Added in Table 4 footnote as “Daily milk yield was calculated as the sum of morning and afternoon milking values.”

Line 128: The phrase “jugular vein of tail” is incorrect. Please specify whether samples were collected from the jugular vein or the coccygeal vein.

Added in line 158.

And

The sentence that “Statistical significance was compared between control and GABA treatment groups using the PDIFF option” was wrong. It was mistake.

So changed sentence as “Statistical significance was compared between the control and GABA treatment groups using the method of repeated measurement.” In line 174.

Results – Tables
Multiple tables labeled “Table 4”.

All labels were corrected.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript examines rumen-protected GABA supplementation on milk yield, milk composition, blood metabolites, and behavioral measures in Holstein cows experiencing summer heat stress. The topic is relevant, but key methodological and reporting gaps still limit confidence in the conclusions, particularly the unclear statistical analysis underlying the reported tables and the need for clearer documentation of diet and intake related procedures.

Abstract

Line 28 to 31: The abstract includes a long definition of the THI in the middle of the materials and methods portion, which interrupts the flow. Consider replacing this with one short sentence stating that cows were exposed to heat stress, then use the saved space to better frame the study question and briefly describe the treatments (including the GABA doses and delivery form). In addition, adding one concise introductory sentence at the beginning of the abstract would help introduce the topic and improve readability.

Line 43 and 44: “GABA supplementation groups of Rest and rumination 43 were significantly lower than those in the control group (p <0.05).” The phrasing is unclear and should be rewritten for clarity and grammar.

Introduction

Line 55: "this duration increased by 19 days to 117 days”. Consider rewriting this for clarity.

Line 60 to 84: This section covers several topics in a single paragraph and the flow is hard to follow. Consider splitting into shorter paragraphs and reducing repetition. For example, heat stress definitions and index thresholds could be consolidated, and the rumen fermentation discussion could be separated from the climate duration context.

Line 97: Since the paragraph begins with “Therefore,” it reads as a continuation of the previous paragraph. Consider merging it.

Material and methods

Line 105: The sentence “The information of dairy cows is presented…” is awkward. Please revise for clarity.

Line 114: The manuscript states that each cow was restricted to 21.26 kg DM per day. Please clarify how this restriction was implemented in practice and how compliance was verified (refusals recorded, confirmation that the full allotment and top dressed supplement were consumed). Also, because cows can differ in body weight and intake capacity (even with similar production, lactation stage, and parity), please justify the choice of a single fixed intake for all animals and discuss how this may affect interpretation. If dry matter intake was fixed and equal across treatments, then increased feeding time cannot be interpreted as increased intake. Please revise the interpretation accordingly, or provide actual intake and refusals data showing differences.

Line 126: THI is derived from a weather station dataset. Is this measurement from the same location as the trial? Could you provide any additional information about the station's temperature?

Milk composition: Please clarify whether milk composition was analyzed from separate morning and afternoon samples and then weighted per yield, or whether samples were composited before analysis. The current text states that 50 mL was collected in the morning and afternoon but does not explain how these were handled analytically. Were the 50 ml of milk analysed separately, and then the composition values weighted by each production time amount? Or were samples combined and then analysed as one sample? Clarify so the reader can understand and repeat what you have done. I'm not referring to milk yield, I'm referring to milk composition.

Line 150: “Jugular vein of neck” is redundant. “Jugular vein” is sufficient.

Table 4: There is a row labeled “< 90” under THI classification, which appears inconsistent with the other bins and likely should be “> 90” or otherwise clarified.

Line 166: The text says five activity states include inactivity, but the table later reports high activity, activity, rest, eat, rumination. Please ensure consistent naming for inactivity or rest in table 3, 8 and text references.

Statistical Analysis

The statistical analysis section is not sufficiently detailed to understand how the reported p values were obtained. The model described in Methods includes only a treatment term (Yij = μ + Tj + Eij) and states that no random effect was considered, yet the Results tables report p values for Week and Treatment × Week. Please clarify the exact model used to generate each table, including which fixed effects were included, and provide the corresponding PROC MIXED specification (or equivalent)

Results

Line 208 and 213: The text refers to “rumen temperature,” but Table 5 defines RT as rectal temperature. Please correct terminology consistently across the Results and tables. Also, RT is only defined in the second mention.

Line 222: rumen temperature mentioned again. Please correct it.

Discussion

Line 236: What is “0w, 236 20240717; 8w, 20240911.” representing here?

Table 6: Is Milk urea nitrogen in mg/mL or mg/dL? Please check.

Line 299: The statement that “THI 72 is set as a threshold since the productivity of Holstein cows starts to decrease” should be made more precise. Please complete the sentence, adding whether the decline begins at THI 72, above THI 72, or at or above THI 72…

Line 317: Please fix reference formatting and ensure all cited studies are included in the reference list. For example, “Rhoads et al., 2009” appears in text but is not shown in the reference list portion provided.

Line 328 to 339: The GABA discussion reads as a compilation of statements rather than a connected narrative. Please reorganize to present a linear argument, for example: proposed mechanism, what your data show, then how your results align or conflict with prior work. Also, caution should be taken when discussing rumen temperature since you did not measure it. You measure rectal temperature.

Line 346: The discussion states that rumen protected GABA prevents decreases in milk protein, but in this study the 6 g treatment tended to have lower milk protein than the other groups. Please address this.

Comments on the Quality of English Language

Overall, the English is understandable and the manuscript is readable. That said, several sentences require refinement for grammar, clarity, and scientific phrasing. I recommend a careful language edit throughout.

Author Response

Answer: Thank you for kind review.

Answer: Deleted line 28-30. And added “Animals were exposed to heat stress conditions (THI ≥ 72) during the experimental period.” In line 30-31

And added sentence as “The basal diet was fed as a total mixed ration (TMR), and GABA was top-dressed onto the TMR.” In line 31-32.

Answer: change to “Rest and rumination times in the GABA supplementation group were significantly lower than those in the control group (p < 0.05).” in line 44-45.

Introduction

Line 55: "this duration increased by 19 days to 117 days”. Consider rewriting this for clarity.

Answer: Change to “whereas they increased to 117 days in the recent period (1988-2017), representing a 19-day extension in exposure to high summer temperatures.” In line 56-57.

Answer: The paragraph structure was changed to combine the heat stress paragraph and the THI paragraph in livestock, and separate the paragraph on rumen heat in line 62 to 92.

Line 97: Since the paragraph begins with “Therefore,” it reads as a continuation of the previous paragraph. Consider merging it.

Answer: merged in line 91-93

Material and methods

Line 105: The sentence “The information of dairy cows is presented…” is awkward. Please revise for clarity.

Answer: Change to “Dairy cow characteristics are presented in Table 1 by experimental treatment.” In line 100.

Answer: added sentence “Each animal was housed in an individual pen for feeding, and residuals were not observed during experimental periods.” In line 111-112.

Also, because cows can differ in body weight and intake capacity (even with similar production, lactation stage, and parity), please justify the choice of a single fixed intake for all animals and discuss how this may affect interpretation. If dry matter intake was fixed and equal across treatments, then increased feeding time cannot be interpreted as increased intake. Please revise the interpretation accordingly, or provide actual intake and refusals data showing differences.

Answer: added sentence ”However, the restricted feeding protocol in this study prevented assessment of GABA's effect on voluntary feed intake, which increased in previous studies.” In line 367-368.

Line 126: THI is derived from a weather station dataset. Is this measurement from the same location as the trial? Could you provide any additional information about the station's temperature?

Answer: Changed to “THI was calculated from temperature and humidity data recorded hourly using an automatic thermo-hygrometer (MHT-381SD, Lutron Electronics Inc., Coopersburg, PA, USA) during the experimental periods.” In line 124 to 126.

Answer: added “Milk components were analyzed from combined samples of morning and afternoon milk.” In line 140-141.

Line 150: “Jugular vein of neck” is redundant. “Jugular vein” is sufficient.

Answer: corrected.

Table 4: There is a row labeled “< 90” under THI classification, which appears inconsistent with the other bins and likely should be “> 90” or otherwise clarified.

Answer: changed "<72" to "under 72" and changed to "<90" to "over 90" in Table 4.

Answer: corrected "inactivity" to "rest" in line 165.

Statistical Analysis

Changed to “Data were analyzed using a MIXED procedure of the SAS 9.4 software (SAS Inst. Inc., Cary, NC, USA) [21] as a completely randomized design. The model was

Yijk = μ + Gi + Wj + GWk + Eikj,

where μ is the average value, Gi is GABA supplementation effect, Wj is time effect, GWk is interaction between GABA and time effect, and Eij is the error value. The fixed effect was GABA, and random effect was not considered. The interaction between GABA supplementation and sampling time was assessed to isolate GABA-specific ef-fects. Statistical significance was compared between the control and GABA treatment groups using the method of repeated measurement [16]. Least square means between treatments were assessed using a pairwise comparison method. Statistical difference and tendency were accepted at a p value less than 0.05 and 0.05<p≤0.10, respectively. All means are presented as least square means.” In Statistical analysis section.

Results

Answer: Corrected “rumen temperature” to “rectal temperature”

Line 222: rumen temperature mentioned again. Please correct it.

Answer: Corrected “rumen temperature” to “rectal temperature”

Discussion

Line 236: What is “0w, 236 20240717; 8w, 20240911.” representing here?

Answer: deleted. It means Experiment start and end date. This information was already presented in the main text and was therefore deleted as redundant.

Table 6: Is Milk urea nitrogen in mg/mL or mg/dL? Please check.

Answer: Corrected to mg/dL.

Answer: corrected as “Generally, a THI threshold of 72 is used, as Holstein cow productivity begins to decline at or above this value.” In line 296-297.

Answer: Added references.

Answer: Discussion section added in line 326 to 340.

Line 346: The discussion states that rumen protected GABA prevents decreases in milk protein, but in this study the 6 g treatment tended to have lower milk protein than the other groups. Please address this.

Answer: added sentence “The other side, a previous study reported a quadratic response to GABA supplementation levels, with milk protein increases being greater at lower doses [22]. These results suggest that milk protein response to GABA is not dose-dependent beyond certain levels.” In line 353-354.

Author Response File: Author Response.docx