Does Environmental Enrichment with Music and Strobe Light Affect Broilers’ Welfare? Analyzing Their On-Farm Reaction
, Douglas D’Alessandro Salgado 2, Marta dos Santos Baracho 1, Nilsa Duarte da Silva Lima 3 and Danilo Florentino Pereira 4,*
Round 1
Reviewer 1 Report
I enclose a file with comments. Please, follow the indications given in the notes.
Comments for author File: 
Comments.pdf
Author Response
On behalf of the authors, I am grateful for the notes made by the reviewer, which contributed to the improvement of the article's writing. I inform you that all the suggested changes were accepted and are highlighted in the article.
Regarding the doubt about when the strobe light was applied in the Light + Music treatment, we confirm that the light was applied after 6 min of music. We seek to clarify this part of the methodology in the text.
Reviewer 2 Report
Materials and Methods section
- Part of the results of this experiment were previously published in an article titled "Effect of Environmental Enrichment on the Body Weight in Broiler Chickens," which appeared in the Brazilian Journal of Poultry Science in 2020. Although it was the same experiment, the materials and methods are not described in the same way. For example, a 2020 article states "In BH1 and BH2 different music styles were played each week to promote motivation for the birds. Every week an amount of four types of sounds were played. The type of sounds were rock, soul, country, jazz, pop, nature, and classical music." However, the proposed manuscript states "Every day, a classical music soundtrack was on for approximately 6 min (ranging from 2-440 Hz and 60-70 dB), played five times a day for six weeks …..” Regarding lighting, the 2020 article states, “The light performed once a day, for five weeks. The duration of the light stimuli was about 6 minutes." However, the present manuscript states "The light was turned on, following the same pattern as the musical stimulus, lasting around 6 min."
- The effect of the sex of the chickens was not considered in the study. Why not, when it is known that sex can significantly affect at least some of the parameters observed in this study (e.g., incidence and severity of pododermatitis)?
- Blinding is an important methodological feature of scientific experiments to minimize bias and maximize the validity of results. Was the person observing/assessing the birds blinded to the treatments? Was intra-observer reliability determined? Although only one person performed all observations, it would have been good to determine interobserver reliability to ensure that the ethogram was well described and valid.
- The description of some procedures is unclear. For example, there is no description of how the authors combined the four indicators of behavior (dust bathing, standing up, preening, stretching) into one indicator - "comforting".
Results and Discussion section
Some results are overgeneralized due to underutilization of statistical tests. For example:
- Lines 186-187: »It can be seen in the graphs of Figure 3 that the birds walked more in the control treatment (Figure 3d), followed by the light treatment.« This is true, but only at the age of 28 days. At 21 days of age, the difference between groups A3 and A4 is not statistically significant, and at 35 days of age, birds walked more in the light treatment (A3) than in the control treatment (A4).
- Lines 187-189: »However, the light stimulus (A3) promoted greater foraging behavior at the age of 21 days (Figure 3e) and reduced the expression of the lying behavior at all ages (Figure 3f).« At 35 days of age, the difference between groups A2 and A3 in laying down behaviour was not statistically significant.
- Lines 194-196: »Comforting behaviors (dust bathing, standing up, preening, and stretching) were observed more frequently in the control treatment (A4) at 21 and 28-day-old broilers. The treatment with light seems to have stimulated the frequency of these behaviors.« The light treatment did not stimulate the comforting behaviors until 35 days of age, and even in this case there was no significant difference between groups A2 (music) and A3 (light).
- Line 202: »The wing flapping reaction decreased with the increase in the age of the chickens.« This statement is not correct. For example, in group A1 at 28 to 35 days of age or in groups A2 and A3 at 28 to 35 days of age, the frequency of wing flapping increased.
- Lines 204-205: »The control results show that the light treatment (A3) had the highest incidence of wings flapping.« It is not clear what is meant by this sentence.
- Lines 205-207: »It was verified that the treatment with light (A3) presented a higher frequency of scratching, stand alert, and attack behaviors for all ages, except for the scratching behavior at 35 days old broilers.« Not even one of the three traits (scratching, stand alert, attack) is more frequent in the A3 group than in the other three groups at all three ages.
Discussion section
The "Discussion" section is poorly written and needs to be thoroughly revised to make sense and flow. Also, similar to the "Results" section, the "Discussion" section often does not present the results concisely enough.
For example:
- Lines 223-225: »The wing flapping decreased as broilers got old, and the frequency of such behavior seen in other ages was nearly the same with music or strobe light stimuli.« The statement in the first part of the sentence is only partially correct.
- Lines 226-227: »The light treatment seemed to have the highest incidence of wings flapping in the control rearing environment.« It is not clear what is meant by the phrase "The light treatment .... in the control rearing environment."
- Lines 236-239: »We found that the comforting behaviors (dust bathing, standing up, preening, and stretching) were more often in the control treatment at 21 and 28-day-old broilers. These reactions increased at 35 days of age in treatment with light stimulus. These results indicate that broilers felt stressed with the tested stimuli.« In Table 2, the authors of the manuscript divided the behavioral indicators into two parts: 1. indicators of well-being behavior and 2. indicators of stress behavior. According to this division, comforting is an indicator of well-being behavior. How then can the increase in frequency of this behavior indicate stress in broiler chickens?
- Lines 250-251: »Our results indicate that broilers walked more in the control treatment and differed from other outcomes.« Looking at the data from Figure 3(d) at 21 and 35 days of age, this statement is not true because broilers at these ages walked more in group A3 (light) than in group A4 (control).
- Lines 256-258: »Our results also showed that grouping enrichments together does not appear to attract a higher number of broiler chickens.« It is not clear what the phrase "attract a higher number of broiler chickens" refers to. How did the author monitor this parameter in the experiment?
The "Conclusions" section contains some vague statements (Line 297: »it is not yet clear if broilers like music«) and is not consistent with the results. Again, there is a large generalization of the results.
Figures 3 and 4: For certain behavioral indicators/age of broilers, it is not indicated whether the differences between treatments are statistically significant or not.
Author Response
On behalf of the authors, I am grateful for the notes made by the reviewer, which contributed to the improvement of the article's writing. All the suggested changes were analyzed and answered point by point, and changes are highlighted in the article.
Part of the results of this experiment were previously published in an article titled "Effect of Environmental Enrichment on the Body Weight in Broiler Chickens," which appeared in the Brazilian Journal of Poultry Science in 2020. Although it was the same experiment, the materials and methods are not described in the same way. For example, a 2020 article states "In BH1 and BH2 different music styles were played each week to promote motivation for the birds. Every week an amount of four types of sounds were played. The type of sounds were rock, soul, country, jazz, pop, nature, and classical music." However, the proposed manuscript states "Every day, a classical music soundtrack was on for approximately 6 min (ranging from 2-440 Hz and 60-70 dB), played five times a day for six weeks ….." Regarding lighting, the 2020 article states, "The light performed once a day, for five weeks. The duration of the light stimuli was about 6 minutes." However, the present manuscript states "The light was turned on, following the same pattern as the musical stimulus, lasting around 6 min."
Answer: Indeed, this is part of a Ph.D. thesis where the student explored several possibilities of using strobe light and music to be used as a broiler house enrichment. In the present manuscript, only the data with the classical music exposure were tested, different from the experiment in the article cited by the reviewer. We separate the effect since most articles in current literature address the effects of classical music on farm animal behavior.
The effect of the sex of the chickens was not considered in the study. Why not, when it is known that sex can significantly affect at least some of the parameters observed in this study (e.g., incidence and severity of pododermatitis)?
Answer: The flocks were mixed. When observing the behavior in the videos, it was not possible to identify the sex of the birds, and, for this reason, we did not consider the sex of the birds. In the case of pododermatitis, we performed a statistical test for the sexes and found no difference. We added this information in the article, including the p-value found (p = 0.371).
Blinding is an important methodological feature of scientific experiments to minimize bias and maximize the validity of results. Was the person observing/assessing the birds blinded to the treatments? Was intra-observer reliability determined? Although only one person performed all observations, it would have been good to determine interobserver reliability to ensure that the ethogram was well described and valid.
Answer: This manuscript is part of a Ph.D. thesis, and the student did her training with Dr. Butterworth at the University of Bristol, UK, where she spent a semester. As for the blinding, since she was aware of the treatments, this was not possible, as mentioned in a sentence in the M & M section of the manuscript. The present manuscript presents partial cohort study results, where treatments were applied to known groups and evaluated over time. Therefore, the videos were watched by an observer who knew about the treatments.
The description of some procedures is unclear. For example, there is no description of how the authors combined the four indicators of behavior (dust bathing, standing up, preening, stretching) into one indicator - "comforting".
Answer: We evaluated the birds' natural behaviors expressed in the recorded videos. The behaviors that made up the "Comforting" were grouped according to the proposal of other authors, and we added references that made a similar approach to the text.
Results and Discussion section
Some results are overgeneralized due to underutilization of statistical tests. For example:
- Lines 186-187: »It can be seen in the graphs of Figure 3 that the birds walked more in the control treatment (Figure 3d), followed by the light treatment.« This is true, but only at the age of 28 days. At 21 days of age, the difference between groups A3 and A4 is not statistically significant, and at 35 days of age, birds walked more in the light treatment (A3) than in the control treatment (A4).
Answer: We corrected the sentence as suggested.
- Lines 187-189: »However, the light stimulus (A3) promoted greater foraging behavior at the age of 21 days (Figure 3e) and reduced the expression of the lying behavior at all ages (Figure 3f).« At 35 days of age, the difference between groups A2 and A3 in laying down behaviour was not statistically significant.
Answer: We corrected the sentence as suggested.
- Lines 194-196: »Comforting behaviors (dust bathing, standing up, preening, and stretching) were observed more frequently in the control treatment (A4) at 21 and 28-day-old broilers. The treatment with light seems to have stimulated the frequency of these behaviors.« The light treatment did not stimulate the comforting behaviors until 35 days of age, and even in this case there was no significant difference between groups A2 (music) and A3 (light).
Answer: we corrected the sentence as suggested.
- Line 202: »The wing flapping reaction decreased with the increase in the age of the chickens.« This statement is not correct. For example, in group A1 at 28 to 35 days of age or in groups A2 and A3 at 28 to 35 days of age, the frequency of wing flapping increased.
Answer: We corrected the sentence as suggested.
- Lines 204-205: »The control results show that the light treatment (A3) had the highest incidence of wings flapping.« It is not clear what is meant by this sentence.
Answer: We corrected the sentence as suggested.
- Lines 205-207: »It was verified that the treatment with light (A3) presented a higher frequency of scratching, stand alert, and attack behaviors for all ages, except for the scratching behavior at 35 days old broilers.« Not even one of the three traits (scratching, stand alert, attack) is more frequent in the A3 group than in the other three groups at all three ages.
Answer: We corrected the sentence as suggested.
Discussion section
The "Discussion" section is poorly written and needs to be thoroughly revised to make sense and flow. Also, similar to the "Results" section, the "Discussion" section often does not present the results concisely enough.
For example:
- Lines 223-225: »The wing flapping decreased as broilers got old, and the frequency of such behavior seen in other ages was nearly the same with music or strobe light stimuli.« The statement in the first part of the sentence is only partially correct.
- Lines 226-227: »The light treatment seemed to have the highest incidence of wings flapping in the control rearing environment.« It is not clear what is meant by the phrase "The light treatment .... in the control rearing environment."
Answer: We corrected the sentence as suggested.
- Lines 236-239: »We found that the comforting behaviors (dust bathing, standing up, preening, and stretching) were more often in the control treatment at 21 and 28-day-old broilers. These reactions increased at 35 days of age in treatment with light stimulus. These results indicate that broilers felt stressed with the tested stimuli.« In Table 2, the authors of the manuscript divided the behavioral indicators into two parts: 1. indicators of well-being behavior and 2. indicators of stress behavior. According to this division, comforting is an indicator of well-being behavior. How then can the increase in frequency of this behavior indicate stress in broiler chickens?
Answer: In this case, we compared all treatments with the control. This statement is correct at 21 and 28 days of age, and only at 35 days of age, the strobe light treatment favors these behaviors. We changed the sentence to be more explicit.
- Lines 250-251: »Our results indicate that broilers walked more in the control treatment and differed from other outcomes.« Looking at the data from Figure 3(d) at 21 and 35 days of age, this statement is not true because broilers at these ages walked more in group A3 (light) than in group A4 (control).
Answer: We changed the sentence.
- Lines 256-258: »Our results also showed that grouping enrichments together does not appear to attract a higher number of broiler chickens.« It is not clear what the phrase "attract a higher number of broiler chickens" refers to. How did the author monitor this parameter in the experiment?
Answer: We agreed it was confusing and removed the sentence.
The "Conclusions" section contains some vague statements (Line 297: »it is not yet clear if broilers like music«) and is not consistent with the results. Again, there is a large generalization of the results.
Answer: We rewrite the conclusions
Figures 3 and 4: For certain behavioral indicators/age of broilers, it is not indicated whether the differences between treatments are statistically significant or not.
Answer: we added the p-value in the pertinent parts of the text.
Reviewer 3 Report
Regarding the manuscript entitled'' Does environmental enrichment with music and strobe light affect broilers’ welfare? Analyzing their on-farm reaction''
Abstract
Please add p value in the abstract.
One conclusion sentence should be added at the end of the abstract.
Introduction
L87-88. Please rephrase
Add hypothesis in the last paragraph of introduction.
Materials and Methods
L162. Add ref
Results
Please add subheadings to be easy for the readers to follow the results
L178-181. Please shorten this sentence. Most of the description should be in footnote of the figure.
Figure 3. Please increase the size and quality of the figure to be easy for the readers
P value should be added in the results section
L190-191. Rephrase
L195-196 please write it clear how it stimulated?
L196-197. Should be in another subheading
L202. The increase should support with p value please add
Author Response
On behalf of the authors, I am grateful for the notes made by the reviewer, which contributed to the improvement of the article's writing. I inform you that all the suggested changes were accepted and are highlighted in the article.
