The Effects of Space Allowance and Toy Provision on the Growth, Spatiotemporal Distribution of Behavior, and Pen Cleanliness of Finishing Pigs

Round 1

Reviewer 1 Report

The submitted manuscript aims to investigate the effect of space and toy availability on finishing pigs. Different outcome variables were investigated, such as average daily gain, lying proportions, excreting proportions and scoring for cleanliness. Generally the paper is very well written, but the statistical methodology considered is not clearly presented in the Methods and Results sections.

Introduction

Lines 73 to 77: In this last paragraph it is presented the aim of the study, that corresponds to the title of the manuscript. However, both do not contemplate growth, evaluated in this study with daily weight gain. The average daily weight gain is one of the outcome variables analysed, is discussed in the Discussion section, and the Conclusion section starts with a sentence including the average daily weight gain. I suggest the inclusion of growth in both the Title and the aim of the study.

Material and Methods

Data analysis

Lines168 to 169: The authors state that “Behavioral indicators were analysed in pigs, while other indicators were analysed in pens.”. I think the behavioral indicators correspond to lying and excreting behaviour of pigs, but as I understand the observation was in pigs, however, the outcome variables analysed were the proportion of pigs with this behaviour in each pen (sections 2.3.2 and 2.3.3), and not the presence/absence of each behaviour in each pig. The sentence must be clarified.

Lines 170 to 174: It is referred that both One-way ANOVA and Two-way ANOVA were performed. The  “3  ×  2  two-factor  experimental  design  (three  levels  of  stocking  density  ×  with/without toys)” seems to call to a Two-way ANOVA. However only “two replicates per treatment” were considered, that is, for each combination of level of stocking density and presence/absence of toys only two pens were observed. If, there was only one pen, I would consider a two-way ANOVA without replication assuming that no interaction is present. In this study, there are two replicates, but it seems to be too small to evaluate the interaction effect in a Two-way ANOVA. The authors refer also the use of One-way ANOVA, but the explanation of how it was performed it is not clear. It is not understandable the meaning of “this test always maintained one of the factors fixed”. The authors did not mention also if the necessary conditions to perform an Analysis of Variance were verified, or if post-hoc analysis was performed. In short, the authors should present in more detail the statistical methods used to analyse the effect of levels of stoking density and the presence/absence of toys in the different outcomes considered.

Results

Throughout the text and tables the presentation of the significant results and P-values is confusing. There seem to be too much P-values. After revising the Methods section the Results section should be revised accordingly.

Table 2: Apart from not being clear what ANOVA model was considered, the reference to “Interaction effects” is confusing since only “Main-effects” are considered. The units used to measure average daily gain should be presented.

Lines 192 to 193: The authors state “The lying behavior of pigs was mainly concentrated in the two periods of 0:00–6:00 and 20:00–23:59 at night,” however this lying behavior correspond to just one period: 20:00 in the evening to 6:00 in the morning. The sentence should be corrected.

Lines 222 to 223: Please check whether instead of “higher” it should be “lower”.

Line 240: Please check whether instead of “higher” it should be “lower”.

The Abstract, the Discussion and Conclusion sections should be should be reviewed after the revision of the Methods and Results sections.

 

Author Response

Dear editor/ reviewer

We would like to thank you for your efforts in reviewing our manuscript titled " Effects of Space Allowance and Toy Provision on the Growth, Spatiotemporal Distribution of Behavior and Pen Cleanliness of Finishing Pigs", and providing many helpful comments and suggestions, which will all prove invaluable in the revision and improvement of our paper, as well as in guiding our research in the future. Here are the details.

Introduction

Lines 73 to 77: We've added growth in both the Title and the aim of the study.

Material and Methods

Data analysis

Lines168 to 169 and lines 170 to 174: We have made corrections to the statistical analysis methods and revised some of the corresponding results.

Results

Table 2: We have re-analyzed the significance involved in Table 2 and made changes in the text.

Lines 192 to 193: “The lying behavior of pigs was mainly concentrated in the two periods of 0:00–6:00 and 20:00–23:59 at night,” has been corrected to “The lying behavior of pigs was mainly concentrated from 8:00 pm to 6:00 am of the next day”.

Lines 222 to 223 and line 240: The description in this section has been rewritten.

Thank you again for your valuable comments and suggestions. I look forward to hearing from you soon in due course.

Yours sincerely,

Hao Wang

Chongqing Academy of Animal Sciences, Chongqing, 402460, China

Reviewer 2 Report

The manuscript is indeed of interest as it deals with topics that significantly impact pig productivity and animal welfare.

However, the degree of innovation cannot be considered high since the elements able to influence the excreting (and resting) behaviour of the pigs have already been the subject of other studies (see, for example, the review by Nannoni et al., 2020,  https://doi.org/10.3390/ani10112025).

That said, my main perplexity concerns the centrality of the effects found by the Authors on the improvement of daily weight gain: in the absence of a sufficient number of replications for each treatment and, above all, in the absence of a recording (individual or per pen) of feed intake, I do not think it is possible to draw solid conclusions on this parameter (ADG).

From a methodological point of view (section 2.3), the Authors do not specify how the behaviours were detected (whether through scan sampling or all occurrences sampling). Likewise, it is not specified how many observers there were, whether they had been adequately trained and what the inter-observer (and possibly intra-observer) variability was.

Regarding statistics, the experimental unit (generally, in this kind of study, should be the pen) is not specified.

The presentation of the statistical analysis results presents considerable interpretative difficulties in all tables, which, in my opinion, need to be radically revised. For example, Table 2 shows the results of the analysis of interactions followed by a post-hoc that would provide better outcomes for the lower stocking density group with toys than the corresponding group without toys. However, the superscripts' role is unclear (superscripts read in the context of columns show no differences).

Regarding lying preferences (3.3), it is unclear where the differences declared in the text in lines 247-260 are shown, as Table 3 reports only the p-values due to main effects (stocking density and toy supply) and Figure 3 shows the behaviours of the 6 groups.  Equally unclear are the significant differences claimed for the cleanliness score reported in lines 271-272 which are not shown in a corresponding Table.

Based on these considerations, I regret to conclude that in my opinion, the work is unfit for publication in its present form. As a result, I suggest radically revising the manuscript, focusing strictly on the behavioural observations (and not on ADG), which should be reported in more immediately understandable tables.

Given that I am not a native speaker, I think the quality of English is good.

Author Response

Dear editor/ reviewer

We would like to thank you for your efforts in reviewing our manuscript titled " Effects of Space Allowance and Toy Provision on the Growth, Spatiotemporal Distribution of Behavior and Pen Cleanliness of Finishing Pigs", and providing many helpful comments and suggestions, which will all prove invaluable in the revision and improvement of our paper, as well as in guiding our research in the future. In response to your comments, we have revised the text and provided the following explanations.

 

For the ADG of pigs, we have supplemented the statistical units in the text. We tested the feed intake of pigs required to calculate ADG in pens in the actual experiment, but considering the difference in statistical units, it is not included in the text. Moreover, AGD is one of the important indicators to measure the growth performance of pigs. Analysis with ADG can also reflect the growth performance of pigs to a certain extent.

For section 2.3, we have added content on sampling methods and observers.

For statistics, we have added clarifications related to statistical units in the text.

For statistical analysis results, we apologize for not showing the statistical results clearly, and we have made specific changes in the text.

Thank you again for your valuable comments and suggestions. I look forward to hearing from you soon in due course.

Yours sincerely,

Hao Wang

Chongqing Academy of Animal Sciences, Chongqing, 402460, China

Round 2

Reviewer 1 Report

Comments on the first version of the manuscript were addressed by the authors in this revised version.