Morpho-Biometric Characterization of the North African (Tunisian) Local Chicken Populations

Nour Elhouda Fehri1,2, Mohamed Aroua1, Safa Bejaoui2, Manel Ben Larbi3, Sami Dridi4 and Bayrem Jemmali2*

1LR14AGR04,Ecole Supérieure d’agriculture du Kef ,Université de Jendouba , Compus Universitaire Boulifa 7119 Kef, Tunisia

2LR13AGR02, Mateur Higher School of Agriculture, University of Carthage, Mateur 7030, Tunisia

3UR17AGR04, Mateur Higher School of Agriculture, University of Carthage, Mateur 7030, Tunisia

4Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, 72701 AR, USA

ABSTRACT

The present study aimed to determine the socio-economic and morpho-biometric characteristics of the local population of chickens in North Africa. A total of 250 chickens were sampled in three regions of the country of Tunisia. A complete description by direct observation, individual weighing, and body parts measurements were determined. The results of the study showed a significant diversity of plumage colors in the studied populations. Birds of the dominant yellow color represent the average proportion of 20 %. Birds with black, gray, and white plumage represent a low proportion (18%, 12%, and 12%, respectively). A great phenotypic diversity was noticed and the ascending hierarchical classification showed the existence of two different groups with differential body weight, body length, back length, comb length and width, ear lobe length and width, wing length, wattle length, neck length, thigh and breast length, shank length and diameter, and central toe length. This phenotypic and descriptive richness can be considered a starting point for categorizing local indigenous Tunisian chickens. Genetic, anatomic, and physiologic large-scale studies are warranted to establish a comprehensive database and improve the conservation and sustainable production of these indigenous chickens.

Article Information

Received 21 January 2023

Revised 20 March 2023

Accepted 03 April 2023

Available online 12 June 2023

(early access)

Published 28 November 2024

Authors’ Contribution

NEF, MA and JB designed the study and wrote the manuscript. NEF, MA,

BS, MBL, SD and BJ performed

the field work. NEF, MA and

BJ analyzed the data.

Key words

Tunisia, Indigenous chickens, Morpho-biometric, Phenotypic, Sustainability

DOI: https://dx.doi.org/10.17582/journal.pjz/20230121170143

* Corresponding author: [email protected]

0030-9923/2025/0001-0019 $ 9.00/00

Copyright 2025 by the authors. Licensee Zoological Society of Pakistan.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

INTRODUCTION

Although the poultry industry supports the subsistence and food security of billions of people worldwide, it is facing several challenges at a global scale from a steep projected increase in international demand for high-quality animal proteins (meat and eggs) and the need to adapt to climate changes and limited natural resources (water, land, and energy) (Espino et al., 2022).

Over the last many years, there is growing public concern about the welfare of farm animals raised under intensive housing systems leading to an inclination towards natural and indigenous poultry products (Mlambo et al., 2022). Rural poultry production is an important sub-sector with better climate-resilient and disease-resistance chickens compared to imported modern commercial strains (Giller et al., 2022). Although their growth performances are limited, indigenous chickens can be additional sources of meat and eggs, revenue stream, and employment (Wilson et al., 2022).

In Tunisia, Indigenous chickens were introduced by the Phoenicians and the Carthaginians (Tixier-boichard, 2006). They are mainly distributed in rural regions such as the northwest, center, and south (Raach-Moujahed, 2011). They are categorized according to their geographical locations (race or population cradles) or phenotypes, with no information on the structure of their population. Although chickens constituted the predominant livestock production in Tunisia with nearly 88 million slaughtered heads in 2020 (Statista, 2020), the exact indigenous chicken population is currently not known and it is estimated to be approximately 12% of all Tunisian poultry production (Onagri, 2022). Additionally, the Indigenous Tunisian chickens are phenotypically heterogeneous, with plumage color multiplicity, and body conformation diversity. For instance, among other parameters, various types of crest (normal, dwarf, etc.) and peaks (simple, double, rosacea, etc.) were noticed, indicating a great degree of diversity that could be used as basis for a conservation genetic programs. It is, therefore, critical to characterize these local populations for subsequent development of conservation program and genetic improvement programs. In this context, the present study aims, as a first step, to characterize Tunisian local chicken populations on morpho-biometric levels.

MATERIALS AND METHODS

In the North West of Tunisia (Fig. 1), three regions (Kef, Jendouba, and Siliana) were visited to make samples as representatives as possible. Selected local farmers were interviewed with a questionnaire focusing on the socio-economic status of the breeders, the history and management of farms, and the productivity and destination of local poultry. Accordingly, 250 animals were sampled. Each animal has been the subject of a phenotypic, direct description, and the qualitative data described related to the characteristics of the plumage, the comb, the shank, and the skin. A morpho-biometric characterization was carried out, including the body weight, body length, back length, tail length, breast length, comb length, comb width, wattle length, beak length, ear lobe length, ear lobe width, neck length, Wing length, thigh length, shank length, and central toe length according to FAO Animal Production and Health Guidelines (FAO, 2013).

All morpho-biometric data, principal component analysis (PCA), and hierarchical ascending classification (HAC) were developed to classify the Tunisian local poultry groups using XLSTAT software (Data Analysis and Statistical Solution for Microsoft Excel, Add in soft Inc., Paris, France 2017). Fisher exact tests were used to compare groups and a significant difference was set at P < 0.05.

RESULTS AND DISCUSSION

Socioeconomic status of the farmers

As depicted in Figure 2, the small-scale farmers (68.5% women and 31.5% men) interviewed were supposed to be the main managers of the farms. 47.9% of them were younger, and 52.1% were older than 50 years. With regards to education levels, 87.7% are illiterate and are generally old women over 60 years old, while 8.2% have received primary education. Generally, the above mentioned farmers have not received any agricultural or technical supervision, everything is either learned by experience or inherited from their parents and ancestors.

 

 

Local poultry management

In the present study, the Indigenous birds were mainly left to forage during the day and confined at night. After hatching, the chicks were allowed free access to forage (free range) with their mothers in open areas close to the house and surroundings. It is clear from the results that 87% of the chickens are managed under a traditional management system. 90% of farmers provided once a day supplementary feed to their chickens, including corn, barley, wheat, and/or household waste. The age of onset of laying is estimated at 7 months. The data shows that the average body weight of local hens in three regions is around 1720 g (±251g).

Morpho-biometric characterization

The results revealed that for the entire tested local hens, the plumage morphology was normal, the beak is curved and the comb is simple. The wattle and comb are red and the eyes are orange. The shank of all individuals lacks cuffs or vulture boots. Overall, 5 different phenotypes were distinguished: red, yellow, black, gray, and white (Fig. 3A). The distribution of these different groups showed that the dominant phenotype was the red plumage (38%). Birds of dominant yellow color, however, represent 20%, followed by black (18%), gray and white (12% each). There is an important interindividual variation that decreases the phenotypic group effect. Derouich (2003) found that 79.96% of the local hens in the Tunisian center-east region are characterized mainly by a normal distribution of feathers (Derouich, 2013). The wide variety of plumage colors observed in this study can be explained by multiple uncontrolled crossings over several decades between different phenotypes, which gives rise to other combinations existing in low proportions (Akouango, 2004).

Three main colors of the skin were observed, including white (84%), pink (6%), and yellow (8%). This confirms those reported in literature (Ouédraogo, 2018). The colors found on the shank are white (24%); green (30%); yellow (36%) and gray (10%) (Fig. 3B and C). Indeed, white shank corresponds to the absence of pigments in the dermis and the epidermis. Yellow shank coloration occurs with the deposition of food xanthophyll pigments in the epidermis (Dana et al., 2010; Eriksson et al., 2008). The presence of the mutation making the shank yellow is a partial consequence of the introduction of commercial strains of high production performance within West African populations (Guisso et al., 2022). Green coloration results, respectively, from the superpositions of a yellow and white epidermis onto a black dermis (Andersson et al., 2020).

The simple crest is very strongly represented with 86%, followed by the double form which represents 14%. The coloration of these ridges is essentially red 92%, but also pink 8%. The simple, red crest is the most present (Fig. 3D and E).

The high phenotypic variability observed in the local hens should be placed in the dynamic perspective of the gradual introduction of hens of industrial strains into village farms, where matings with the local strain take place either in an uncontrolled manner or to rapidly improve the growth performance of animals.

This color variation could have a certain advantage for breeders because, without means of labeling, the breeders use certain traits, such as feather color and structures to distinguish individuals.

 

Quantitative measurements

The statistical processing of quantitative measurements shows that the average body weight (BW) of local hens in the three regions is 1,713±258g. The minimum recorded weight is 1,195 g, while the largest was 2,440 g (Table I). Regarding the body characteristics, the average body length (LC) is 47.8 ± 4.19 cm, back length (LD=15.3 ± 1.65 cm), tail length (LQ= 15 ± 2.35 cm), breast length (LP=13.4 ± 2.25 cm), while the average value of the breast girth (TP=32.2 ± 2.25 cm). Statistical analysis shows that at head level; comb length (Loc=4.5 ± 1.14 cm), comb width (LW=1.9 ± 0.89 cm), wattle length (LB=2.3 ± 0.56 cm), break length (LM=2.6 ± 0.41 cm), ear lobe length (LO=2.2 ± 0.44 cm), ear lobe width (LY=1.6 ± 0.36 cm). About the leg thigh length (LS=12.1 ± 1.45 cm), shank length (LT=7.5 ± 1.16 cm), shank diameter (DT=4.7 ± 0.86 cm), and Central toe length (LR=6.2 ± 0.78 cm) (Table I).

 

Table I. Characteristics of local hen classes identified.

Variable	Observations	Range	Mean±SD
PC (kg)	250	1.195-2.44	1.71±0.26
LC (cm)	250	37.00-57.00	47.88±4.19
LD (cm)	250	11.00-19.00	15.32±1.65
LQ (cm)	250	10.00-21.00	15.02±2.35
LP (cm)	250	9.50-20.00	13.49±2.25
TP (cm)	250	25.00-39.00	32.26±3.23
LoC (cm)	250	2.50-8.00	4.56±1.14
LW (cm)	250	0.25-4.00	1.96±0.89
LB (cm)	250	1.00-3.50	2.35±0.56
LM (cm)	250	2.00-3.50	2.61±0.42
LO (cm)	250	1.50-3.50	2.24±0.44
LY (cm)	250	1.00-2.50	1.65±0.36
LU (cm)	250	6.00-14.00	10.30±1.70
LA (cm)	250	46.00-78.00	66.46±6.39
LS (cm)	250	9.00-15.00	12.19±1.54
LT (cm)	250	4.00-12.00	7.50±1.16
DT (cm)	250	3.50-7.50	4.77±0.87
LR (cm)	250	4.00-8.00	6.28±0.79

 

PC, Body weight; LC, Body length; LD, Back length; LQ, Tail length; LP, breast length; TP, Breast girth; Loc, comb length; LW, comb width; LB, wattle length; LM, break length; LO, ear lobe length; LY, ear lobe width; LU, neck length; LA, Wing length wingspan; LS, Thigh length; LT, Shank length; DT, Shank diameter; LR, Central toe length.

 

 

In an attempt to better understand the common origins of local hens reared in the visited regions, PCA was performed on the same quantitative variables. The Projection of the variables on the first two axes (LC and LW) of the PCA represents nearly 78.28 % of the total variability (Fig. 4). The special distribution of observation reveals the presence of two groups of Indigenous chickens, but the dissimilarity between them has not been determined. For this reason, a Hierarchical Ascending Classification (HAC) was established and confirmed the presence of two groups (Fig. 5, Table II).

 

Table II. Characteristics of local hen classes identified after CAH analysis.

Variable	Group 1 (61.6%)	Group 2 (38.4%)	Pr > F
PC ( kg)	1.76±0.29	1.63±0.18	< 0.0001
LC (cm)	48.93±3.19	46.19±4.97	< 0.0001
LD (cm)	15.29±1.80	15.35±1.38	0.797
LQ (cm)	15.55±2.36	14.16±2.07	< 0.0001
LP (cm)	13.87±2.50	12.85±1.56	0.0004
TP (cm)	32.61±3.21	31.69±3.18	0.027
LoC (cm)	4.43±1.11	4.77±1.15	0.024
LW (cm)	1.97±0.97	1.96±0.75	0.926
LB (cm)	2.32±0.53	2.39±0.59	0.366
LM (cm)	2.63±0.42	2.58±0.40	0.341
LO (cm)	2.21±0.43	2.28±0.44	0.242
LY (cm)	1.63±0.36	1.68±0.38	0.355
LU (cm)	10.51±1.34	9.97±2.11	0.015
LA (cm)	67.37±5.04	65.00±7.85	0.004
LS (cm)	12.21±1.65	12.16±1.35	0.786
LT (cm)	7.33±1.27	7.78±0.87	0.003
DT (cm)	4.93±0.84	4.51±0.84	0.0001
LR (cm)	6.29±0.85	6.27±0.65	0.819

 

For abbreviation see, Table I.

 

The phylogenetic tree (Table II) obtained from the different morpho-biometric parameters illustrates the relationships between two groups of local hens in the mountainous areas of northern Tunisia. This phylogenetic tree highlights the relationship between the two groups. The first group (n = 154) corresponds to large hens with the highest body weight 1,763 ± 286 g, body length 48.9 ± 3 cm, back length 15.2 ± 1.8 cm, tail length (15.5 ±2.3), breast length (13.8 ± 2.5 cm), breast girth (32.6 ± 3.2), comb length and comb width (4.4 ± 1.1 cm and 1.9 ± 0.9 cm), Wattle length (2.3 ± 0.5 cm), beak length (2.6 ± 0.4 cm), ear lobe length and ear lobe, ear lobe width (2.2 ± 0.4 cm and 1.6 ± 0.3 cm), neck length (10.5 ± 1.3 cm), Wing length wingspan (67.3 ± 5 cm ), tight length ( 12.2 ±1.6 cm), length and diameter of the shank (7.3 ± 1.2 cm and 4.9 ± 0.8 cm) and central toe length (6.2 ±0.8 cm).

The hens of group two (n=96) are a small group having a body weight of 1,633 ± 176 g body length of 46.1 ± 4 cm, the back length of 15.3 ± 1.3 cm, tail length (14.1 ±2), breast length (12.8 ± 1.5 cm), breast girth (31.6 ± 3.8), comb length and comb width (4.7 ± 1.1 cm and 2.3 ± 0.5 cm), wattle length (2.3 ± 0.5 cm), beak length (2.5 ± 0.4 cm), ear lobe length and ear lobe, ear lobe width (2.2 ± 0.4 cm and 1.6 ± 0.3 cm), neck length (9.9 ± 2.1 cm), Wing length wingspan (65 ± 7.8 cm ), tight length (12.1 ±1.3 cm), length and diameter of the shank (7.7 ± 0.8 cm and 4.5 ± 0.8 cm) and central toe length (6.2 ±0.6 cm).

The results show that, except for the (LD, LW, LB, LM, LO, LY, LS, and LR), the other measurement’s parameters are significantly different between the two chicken groups. All averages are higher in the first group, for this reason, group one is the most reared chickens in Tunisia and a genetic amelioration for this group is well recommended.

Body weight varied between phenotypes, with an average of 1,713±150 g. The hens with red plumage presented in group 1 have the highest weight with 1,784g, on the other hand, the hens with beige and black plumage presented in the second group are the lightest with 1,700 g and 1,648 g, respectively. The 18 weeks old hens obtained in this study are heavier than those reported by Raach-Moujahed (2011) in Tunisia (1,620g), or even in some African countries such as Cameroon (Keambou et al., 2007) or Chad (Hasaballah et al., 2015). On the other hand, they are close to native breeds in South Africa or Tanzania, where the values indicated varied from 1,621 to 2,915g. Moula et al. (2009b) indicated on their part that the average weight of the Kabyle hen (Thayazit lekvayel) is 1,820 g. However, Tixier-Boichard et al. (2006) has reported heavier weights of French and American breeds respectively.

CONCLUSION

Taken together, the present descriptive study found that Tunisia indigenous chickens have large morpho-biometric variabilities. Discriminant factor analysis and ascending hierarchical classification highlight 2 different types of groups according to quantitative measurements. Genetic characterization would therefore be a very important next step to support such a classification. Studies on a larger scale, and different Tunisian regions as well as molecular genetic analyses, are however necessary to have a more complete database on the local hens in the country.

ACKNOWLEDGMENTS

We thank the Higher School of Agriculture team, especially Amraoui Marouane and Arbi Tarek.

Funding

There is no specific funding source.

IRB approval

Research activities were approved by the ESA Kef Doctoral Committee (2019).

Ethical statement

This study was approved by the Ethics Committee of ESAM, Tunisa (Approval No: 04-2021).

Statement of conflict of interest

The authors have declared no conflict of interest.

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