Phenotypic Characterization of Local Chickens in West Africa: Systematic Review

Round 1

Reviewer 1 Report

The manuscript “Phenotypic characteristics of local chickens in West Africa: Systematic review” is a systematic review about the Phenotypic characteristics in indigenous chicken of West Africa. My main criticism is that although the review is ambitious, the authors do not delve into most of the aspects studied. In particular there is no true phenotypic description of the populations present in West Africa, there is no elaboration of the data of the consulted publications, it would be useful to propose a clear classification of the phenotypic characteristics, re-elaborate the data on the proposed classification and add images and graphs showing both the illustrated characteristics and the geographical location of the tested populations and their characteristics. The addition of images showing the geographical distribution of phenotypic characteristics could greatly improve the work. As well as the addition of an elaboration that tries to define the phenotypic characteristics of the populations present in the different geographical regions that can allow the reader to understand if on the analyzed territory it is possible to identify different local races.

In addition, many statements are included in the text on the genetic basis of phenotypic observations that are often incorrect and should be supported by genetic data that are not the subject of this paper.

I think that the review's research questions do not agree with the job title: "What are the common descriptions of traditional local chicken populations in West Africa and what explains these characteristics? / Phenotypic characteristics of local chickens in West Africa

You want to describe the parameters used in Africa for the phenotypic description of poultry populations (these have already been defined by the FAO) or report the poultry populations present in West Africa and their phenotypic descriptions?

3. Results

Figure 1: not is clear in the last step “Inclusion” how you select the 22 papers starting from 44.

I think there was some problem in the search method used: you report that Google Scholar (anywhere in the article): ("Local chickens" OR "Native chickens" OR "indigenous chickens") AND (characterization OR Description) AND (Phenotypic OR “Morpho biometric”) AND " Africa" -Review -synthesis… have been used but is not included in the selected articles the review “Local Chicken Breeds of Africa: Their Description, Uses and Conservation Methods” doi:10.3390/ani10122257.

I think this should have been included, other interesting works have probably been wrongly excluded.

In my opinion, the Table A1 is not necessary.

3.3. Features of the plumage

I believe that for the phenotypic description the indications given in the FAO document should be used: the authors should try to revise the data present in the consulted publications and make them conform to the criteria reported in the FAO document.

I think it is better to mention the FAO document in English ( FAO. 2012. Phenotypic characterization of animal genetic resources. FAO Animal Production and Health Guidelines No. 11. Rome pag 107-113https://www.fao.org/publications/card/en/c/8b57fb26-2c80-5ec8-b5e0-4be2cc365831/) rather than in French [11] and to report in the draft and table 1 the same English terms used in it:

·       Feather morphology: normal, frizzle, silky,

·       Feather distribution: normal, naked neck, feathered shanks and feet, muffs and beard,  crest, vulture hocks

·       Plumage pattern (the colour pattern of feathers, if necessary stating the specific location on the body of the birds): plain, barred (specify if sex linked or autosomal), laced, mottled

·       Plumage colour: white, black, blue, red, wheaten

A consultation of the most recent FAO publications is necessary for this review.

Data on the effective size of populations, breeding areas, productive data, etc. are missing.

LINE 140-142: Percentages of chickens with a smooth structure of feathers very often exceed 80% which suggests population are not in Hardy Weinberg equilibrium (Why???) as the curly phenotype is governed by an allele dominant over the normal structure of feathers [26,27].

I do not understand this declaration, it could be that the normal recessive allele, has a very high frequency in the population and that no selection is made towards the dominant allele.

linea 142-148 not clear

Linea 158-160: Indeed, the mutations "naked" and "naked without scales on the legs" are both recessive. Therefore, their maintenance and proliferation within a population would require a constant and sustained effort.

This is not correct, the frequency of recessive variants in a population in HW balance should not change over time. The lack of recessive phenotype may be due to an association with an ectrodactyly due to a mutation in the sc gene leading to a natural selection of the recessive allele.

3.4. Characteristic of the skin and its extensions

I’m not sure that for the authors it is clear that the color of the skin and legs are the same genetic character.  As reported in Eriksson, et al 2008 ( https://doi.org/10.1371/journal.pgen.1000010):  The majority of chickens used for commercial egg and meat production in the Western world are homozygous for the yellow skin allele. In live birds, the phenotype is most easily recognized by the presence of yellow legs.

Line 191-194 :”The presence of the mutation giving the yellow color to the legs to be partly the consequence of the introduction of commercial strains of high production performance within West African”. Lack of bibliographic references or scientific evidence to this report. Dana et al. 2010 (doi:10.1017/S2078633610000652)  reported that “Yellow skin is an abundant phenotype among domestic chickens and is caused by a recessive allele (W*Y) that allows deposition of yellow carotenoids” but the skin color is not evident if in the feeding there are no carotenoids. In addition, they reported that in Ethiopia “Most of the chickens in the high altitude regions have yellow skin”

3.4.3. Types of combs

Also for combs I recommend to use the nomenclature given in the FAO document:

·       Comb type: single, pea, rose, walnut, cushion, strawberry, duplex, V-shaped, double

·       Comb size: small, medium, large

Line 200-203: “However, none of these studies identified the so-called walnut crest shape. Knowing that this last form of crest is the result of the conjugated expression of the genes responsible for the forms of rosacea crest and peas, its total absence in these populations seems abnormal." (ref 27, 2000).

Wright et al in 2009 (https://doi.org/10.1371/journal.pgen.1000512) reported that “chicken with a pea comb has one of two possible gene combinations: rrPP or rrPp. When at least one copy of each gene is present, the result is a walnut comb.”

While et al. in 2012 (10.1371/journal.pgen.1002775) claimed that “Rose-comb, a classical monogenic trait of chickens, is characterized by a drastically altered comb morphology compared to the single-combedwild-type. Here we show that Rose-comb is caused by a 7.4 Mb inversion on chromosome 7 and that a second Rose-comb allele arose by unequal crossing over between a Rose-comb and wild-type chromosome.”

I want to emphasize that although the authors have made a great effort to compile this information, which is presumably scarce in many cases, in my opinion, the quality of the presentation makes it not acceptable for publication in Poultry.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The Authors proposed a critical description of the major phenotypic characteristics of local chickens in West Africa.

I have some suggestion for improve the manuscript.

I think that the economic scenario of West Africa countries is an important discussion topics. So, even if few papers reported the agroecological conditions or the zootechnical conditions, a little section with a description of economical trend of poultry breeding in these countries should be added to the manuscript. Furthermore, I think the section “Limitations of the review” should be add to the “Introduction” section.

Line 97: please change “:” with “.”

In the “Conclusion” section please add a comment about the future economical perspectives of poultry breeding in West African countries.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

the draft has been revised and corrected according to the indications. The work has improved to an acceptable level for publication in the journal

Reviewer 2 Report

The paper is well improved and I think the questions raised were now satisfactorily answered. I only suggest an English revision.