Phenotypic characterization of indigenous non-descript Tarai fowl from the Eastern Himalayan Foothills of India

Introduction

Indigenous poultry genetic resources are vital components of livestock biodiversity, contributing significantly to food and nutritional security, rural livelihoods, and the sustainability of low-input farming systems, particularly in developing countries (FAO, 2015) [3] . Reared predominantly under backyard scavenging conditions, these birds are well adapted to local agro-climatic environments and are valued for their disease resistance, foraging ability, broodiness, and resilience under minimal management (Miao et al., 2005; Padhi, 2016) [13,14] . India possesses rich indigenous poultry diversity, including several registered breeds and numerous uncharacterized populations that have evolved through natural selection and traditional farmer selection over generations (NBAGR, 2021) [10] . However, indiscriminate crossbreeding and the increasing introduction of commercial poultry strains have accelerated genetic erosion, highlighting the need for systematic identification, characterization, and conservation of indigenous genetic resources (FAO, 2012) [4] . www.extensionjournal.com Phenotypic characterization is the first step in the documentation and conservation of animal genetic resources, providing baseline information on morphological, productive, reproductive, and adaptive traits essential for breed identification and genetic improvement (FAO, 2011) [5] . Indigenous chickens generally exhibit lower production than commercial breeds under intensive management but outperform them under backyard production systems due to their superior adaptability, survivability, reproductive fitness, and tolerance to local diseases (Padhi et al., 2015; Rajkumar et al., 2021) [15,16] . The Tarai region of northern West Bengal, located in the foothills of the Eastern Himalayas, is characterized by a humid subtropical climate, high rainfall, and extensive backyard poultry farming. Rural households have traditionally maintained a distinct indigenous non-descript chicken population that is well adapted to the local environment and contributes to household nutrition, income generation, and livelihood security. Despite its apparent uniqueness and socio-economic importance, this population has not been scientifically characterized, and baseline information on its phenotypic and productive attributes remains scarce. Therefore, the present study was undertaken under the Network Project on Animal Genetic Resources of West Bengal, funded by ICAR-National Bureau of Animal Genetic Resources (ICAR-NBAGR), Karnal, Haryana, and implemented by the West Bengal University of Animal and Fishery Sciences during 2023-2025, to comprehensively characterize the phenotypic, morphometric, production, reproductive, and adaptive attributes of this indigenous chicken population, herein designated as Tarai Fowl. The findings are expected to support its conservation, genetic improvement, and formal recognition as a distinct indigenous poultry genetic resource.

Materials and Methods

Study Area

The study was carried out in the native breeding tract of the indigenous Tarai Fowl in the Tarai region of the Eastern Himalayan foothills of northern West Bengal, covering representative villages of Jalpaiguri, Alipurduar, and Cooch Behar districts. The surveyed blocks included Maynaguri, Jalpaiguri Sadar, Cranti, and Malbazar in Jalpaiguri; Alipurduar, Falakata, Kalchini, and Kumargram in Alipurduar; and Sitai, Sitalkuchi, and Mathabhanga in Cooch Behar. The study area lies between 26.3°-26.6° N latitude and 88.7°-89.5° E longitude and is characterized by a humid subtropical climate, annual rainfall of 2,500-3,500 mm, and an integrated crop-livestock production system. Indigenous chickens are traditionally reared under backyard scavenging conditions with minimal external inputs. Owing to their long-term adaptation to this unique agro-ecological region, this indigenous non-descript chicken population is locally recognized as the Tarai Fowl of West Bengal.

Sampling Strategy and Data Collection

A multistage stratified sampling design was employed between 2023 and 2025 to obtain representative coverage of the indigenous non-descript chicken population of the Tarai region. Initially, villages with a predominance of backyard poultry production were identified in consultation with local veterinary personnel and extension functionaries.

Subsequently, households maintaining indigenous chickens continuously for at least five years and practicing traditional backyard management were selected for inclusion in the study. A total of 1,300 adult birds representing both sexes were phenotypically evaluated, while production and reproductive performance data were collected from approximately 900 laying hens maintained under backyard production systems. Information on flock structure, management practices, feeding regime, housing, health care, breeding practices, and production performance was collected through direct field observations, individual animal measurements, and structured interviews using a pretested questionnaire developed in accordance with the characterization guidelines of the FAO (2011) and ICAR-NBAGR (2021) [5,10] .

Phenotypic and Morphometric Characterization

Phenotypic characterization was carried out following the standard descriptors for poultry genetic resources prescribed by FAO (2011) and ICAR-NBAGR (2021) [4,10]. Both qualitative and quantitative traits were recorded. Qualitative traits included plumage colour and pattern, skin colour, shank colour, comb type, comb colour, earlobe colour, eye colour, beak colour, feather distribution, and other externally visible breed-specific characteristics. Quantitative traits included body weight at hatch, 8 weeks, 12 weeks, 24 weeks and 52 weeks (adult age), together with other morphometric measurements wherever applicable. Body weight was recorded using a calibrated digital weighing balance with an accuracy of ±1 g. Linear body measurements and comb dimensions were recorded using a calibrated digital vernier caliper and measuring tape as appropriate. All measurements were obtained following standardized procedures to minimize observer bias and measurement error.

Growth and Production Performance

Growth performance was assessed by recording body weight at predetermined age intervals from hatch to adulthood. Production performance was evaluated using records maintained by farmers together with periodic field monitoring. Parameters recorded included age at first egg, annual egg production per hen, clutch size, clutch length, clutch interval, brooding behaviour, and laying cycle. Annual egg production was calculated as the average number of eggs produced per hen per year under backyard production conditions.

Egg Quality Assessment

Egg quality characteristics were evaluated using freshly laid eggs collected randomly from representative households across the study area. Egg weight was measured using a calibrated digital balance with an accuracy of 0.01 g. Eggshell colour was recorded through visual assessment and classified into cream and brown categories. Owing to the extensive backyard production system and field conditions, internal egg quality parameters, including albumen and yolk characteristics, were assessed only where feasible following standard poultry egg quality evaluation procedures (Sreenivasaiah et al., 2018) [19] . www.extensionjournal.com

Reproductive Performance

Reproductive performance was evaluated under the prevailing backyard production system using natural mating and natural incubation. Parameters recorded included broodiness behaviour, fertility, hatchability on total egg set basis, and hatchability on fertile egg basis. Fertility percentage was calculated as the proportion of fertile eggs to the total number of eggs set for incubation, while hatchability percentages were calculated according to standard poultry breeding procedures.

Mortality Assessment

Mortality data were collected for three age groups, namely 0-1 week, 1-8 weeks, and 8-20 weeks, through farmer records, recall information, and periodic field verification. Mortality percentage for each age group was calculated as the ratio of the number of birds that died during the specified period to the total number of birds present at the beginning of that age interval, expressed as a percentage.

Statistical Analysis

The collected data were compiled, coded, and validated prior to statistical analysis. Descriptive statistical parameters including mean, standard deviation (SD), standard error (SE), minimum, maximum, frequency, and percentage were computed as appropriate. Continuous variables are presented as mean ± standard error (SE), whereas qualitative traits are expressed as frequencies and percentages. Statistical analyses were performed using IBM SPSS Statistics Version 26.0 (IBM Corp., Armonk, NY, USA) and Microsoft Excel. Graphical representations were generated using Microsoft Excel.

Results

Phenotypic Characteristics

The indigenous Tarai fowl population exhibited a high degree of phenotypic uniformity across the surveyed districts, indicating the existence of a relatively stable indigenous population. Adult males were predominantly characterized by a combination of red and black plumage, whereas females generally possessed light brown plumage. A solid plumage pattern was the most frequently observed phenotype in both sexes. The birds exhibited predominantly yellow skin, whitish shanks, black eyes, and uniformly red combs and earlobes. Among the different comb types observed, the single and pea comb was the predominant type. The average comb size was recorded as 1.05 cm. Chick plumage colour closely resembled that of the dam, suggesting consistency in the inheritance of plumage characteristics.

Flock Structure and Management Practices

The indigenous Tarai fowl were reared predominantly under traditional backyard scavenging systems with minimal external inputs. The average flock size maintained by rural households was 8.5 birds, comprising approximately 15% cocks, 65% hens, and 20% chicks. Birds depended primarily on scavenging for feed, supplemented occasionally with household kitchen waste and locally available grains. Housing facilities were generally rudimentary, with birds being sheltered only during the night in simple kutcha structures to protect them from predators and adverse weather conditions.

Growth Performance

The growth performance of Tarai fowl under backyard production conditions is presented in Table 1. The mean hatch weight of chick was 31± 0.08 g. At eight weeks of age, male chicks attained an average body weight of 285.0 ± 2.6 g, whereas female chicks weighed 257.0 ± 2.3 g. By 12 weeks of age, body weight increased to 425.0 ± 3.1 g in males and 397.0 ± 2.9 g in females. The average adult body weight at 24 weeks reached 775.0 ± 2.4 g in males and 765.0 ± 2.1 g in females. The average adult body weight at 52 weeks reached 1750.0 ± 5.6 g in males and 1455.0 ± 4.8 g in females Sexual dimorphism in body weight became evident from eight weeks of age onward, with males consistently exhibiting higher body weights than females throughout the subsequent growth period.

Egg Production Performance

The egg production characteristics of Tarai fowl are presented in Table 2. The mean age at first egg was 205 ± 1.3 days, with individual birds commencing laying between 180 and 214 days. Average annual egg production was 87 ± 1.1 eggs per hen, ranging from 60 to 98 eggs. The birds exhibited a distinct clutch-type laying pattern, with an average clutch size of 8.5 ± 0.4 eggs followed by a clutch interval of 18.0 ± 0.6 days. The average laying period extended for 12.0 ± 0.5 months, while the average age at disposal of hens under backyard production conditions was 22.0 ± 0.7 months.

Egg Quality Traits

The egg quality traits of indigenous Tarai fowl are presented in Table 3. The average egg weight was 41.75 g, ranging from 36 to 52 g. The average shell, albumen and yolk weights were 3.98 g, 15.37 g and 13.32 g, with ranges of 3.07-5.00 g, 10.12-19.60 g and 11.20-16.30 g, respectively. The average shell thickness was 0.59 mm, ranging from 0.38 to 0.82 mm. The average specific gravity, albumen index, yolk index and Haugh unit were 1.07, 65.70, 0.28 and 67.00, respectively. Eggshell colour was predominantly cream in 80% of the eggs, while 20% had brown shells. Albumen quality was predominantly thin in 93% of the eggs, with only 7% exhibiting thick albumen. Egg inclusion bodies were observed in a small proportion of eggs, with blood spots occurring in 3.33% and meat spots in 13.33% of the samples.

Reproductive Performance

The reproductive performance of Tarai fowl is presented in Table 4. Hens exhibited pronounced natural broodiness, a characteristic consistently observed under traditional backyard management. Mean fertility was 70.0 ± 2.1%, ranging from 55 to 89%. Hatchability on a fertile egg basis averaged 85.0 ± 1.9%, while hatchability on a total egg set basis was 64.0 ± 2.3%, demonstrating satisfactory reproductive efficiency under natural incubation.

Carcass Characteristics

The carcass characteristics of indigenous Tarai fowl revealed distinct sex-wise differences as presented in Table 6. Male birds were slaughtered at an average age of 56 weeks with a range of 49-63 weeks, whereas females were www.extensionjournal.com slaughtered slightly later at an average age of 58 weeks with a range of 51-67 weeks. The average hot carcass weight was higher in males at 875 g with a range of 852-891 g than in females at 675 g with a range of 631-688 g. Similarly, the average cold carcass weight was 857 g with a range of 832-876 g in males and 643 g with a range of 617-664 g in females. The average hot dressing percentage was 57.56%, ranging from 42.37% to 68.21% in males, and 55.78%, ranging from 48.21% to 71.39% in females. The corresponding average cold dressing percentage was 56.38%, ranging from 46.21% to 67.54% in males, and 53.14%, ranging from 39.87% to 71.39% in females. The average meat-to-bone ratio was higher in males at 1.79 than in females at 1.62, indicating superior carcass yield and meat recovery in male Tarai fowl.

Mortality Pattern

The age-wise mortality pattern of Tarai fowl is presented in Table 5. The highest mortality (35.0 ± 1.8%) occurred during the first week after hatching. Mortality subsequently decreased with advancing age, recording 12.0 ± 1.2% during the 1-8 week age group and 7.0 ± 0.9% during the 8-20 week age group. These observations indicate that the early brooding period represents the most critical stage for chick survival under backyard production systems.

Utility and Adaptive Characteristics

Tarai fowl were primarily maintained as a dual-purpose indigenous chicken for household egg production and meat. The birds exhibited excellent adaptability to low-input scavenging production systems and demonstrated efficient foraging ability, tolerance to prevailing environmental conditions, and apparent resilience to commonly encountered poultry diseases. Farmers consistently reported that the birds required minimal management inputs while maintaining satisfactory production and reproductive performance under traditional backyard conditions.

Discussion

The present investigation represents the first comprehensive scientific characterization of the indigenous chicken population traditionally reared in the Tarai region of the Eastern Himalayan foothills of India. The study revealed a relatively uniform phenotypic profile, moderate growth and reproductive performance, and remarkable adaptability under low-input backyard production systems. Collectively, these findings demonstrate that Tarai Fowl constitutes a valuable locally adapted poultry genetic resource with considerable importance for sustainable rural poultry production and biodiversity conservation.

Phenotypic Characteristics and Population Identity

Phenotypic characterization is the fundamental step in identifying and documenting animal genetic resources and provides the basis for breed recognition, conservation planning, and genetic improvement (FAO, 2011) [3] . The predominance of red-and-black plumage in males and light brown plumage in females, together with yellow skin, whitish shanks, red earlobes, and the predominance of the walnut comb, indicates a relatively stable and recognizable phenotypic profile within the Tarai fowl population. The consistency of these qualitative traits across the surveyed districts suggests prolonged adaptation under similar ecological conditions coupled with continuous farmermediated selection.

The humid subtropical climate of the Eastern Himalayan foothills, characterized by high rainfall, dense vegetation, and year-round scavenging opportunities, may have contributed to the maintenance of these characteristic phenotypes through natural selection. Plumage coloration may provide improved camouflage against predators in semi-forested environments, while morphological traits such as skin pigmentation, comb morphology, and feather characteristics are often associated with adaptation to local climatic conditions and disease pressures. Similar patterns of phenotypic stabilization have been reported in indigenous chicken populations from Asia and Africa that have evolved under prolonged geographical isolation and traditional backyard management systems (Miao et al., 2005; Padhi, 2016) [13,15] . The observed phenotypic uniformity therefore supports the recognition of Tarai Fowl as a distinct locally adapted indigenous chicken population in accordance with the characterization principles recommended by FAO (2011) [4] .

Growth Performance

The growth performance recorded in the present study reflects the biological characteristics typically associated with indigenous chickens maintained under scavenging production systems. Although the adult body weight of Tarai Fowl (775 g in males and 765 g in females) is considerably lower than that of specialized commercial broiler strains, it falls within the range reported for several indigenous chicken populations reared under extensive management systems worldwide (Halima et al., 2007; Islam et al., 2014) [8,12] . The relatively slow growth rate is not necessarily a limitation but rather represents an adaptive strategy developed under resource-constrained environments. Indigenous chickens allocate available nutrients not only towards body growth but also towards survival, disease resistance, reproductive fitness, and maintenance under fluctuating nutritional conditions. Such physiological adaptation enables them to perform efficiently despite irregular feed availability and minimal management interventions. Similar observations have been reported for indigenous Indian breeds including Aseel, Ghagus, and Nicobari, which exhibit comparatively lower growth rates than commercial breeds while maintaining superior survivability, longevity, and adaptability under backyard conditions (Rajkumar et al., 2021) [17] . Furthermore, increasing consumer preference for naturally reared, slow-growing chickens with superior meat flavour and texture has renewed interest in indigenous poultry genetic resources. Consequently, the moderate growth performance of Tarai Fowl should be viewed within the context of sustainable poultry production rather than intensive commercial farming.

Egg Production and Reproductive Performance

The annual egg production of approximately 87 eggs per hen indicates satisfactory laying performance under traditional backyard management. This production level compares favourably with reports from many indigenous chicken populations maintained under similar scavenging systems in Africa and South Asia, where annual egg production generally ranges from 40 to 80 eggs per hen (Gueye, 2005; Dessie et al., 2011) [6,2] . Comparable performance has also been documented in indigenous chickens reared in eastern India and neighbouring regions under low-input management systems (Padhi et al., 2015; Singh et al., 2018) [15,18] . [9,17,11,1] . The dressing percentages obtained in the present study are comparable to those reported for other indigenous chicken populations reared under backyard systems, indicating acceptable carcass yield despite slower growth than commercial broilers. The higher meat-to-bone ratio in males further suggests superior edible meat recovery. Combined with their adaptability, efficient scavenging ability, and low management requirements, these carcass attributes highlight the potential of Tarai Fowl as a valuable dual-purpose indigenous genetic resource for sustainable backyard poultry production and conservation. www.extensionjournal.com

Conclusion

The present study represents the first comprehensive phenotypic and performance characterization of the indigenous Tarai Fowl of the Eastern Himalayan foothills of West Bengal, India, generating baseline information on a previously undocumented poultry genetic resource. The findings demonstrate that Tarai Fowl possesses distinct phenotypic characteristics, moderate growth and egg production, satisfactory reproductive and carcass performance, and excellent adaptability to low-input backyard production systems. Its efficient foraging ability, strong broodiness, resilience under humid subtropical conditions, and efficient utilization of locally available feed resources make it a valuable genetic resource for sustainable rural poultry production. Despite its comparatively lower productivity than commercial chicken strains, Tarai Fowl plays an important role in supporting household food and nutritional security, supplementary income, and the conservation of indigenous poultry biodiversity. However, the increasing replacement of native chickens by commercial breeds poses a significant threat to its genetic identity. Therefore, strategic conservation through community-based in situ conservation, selective breeding, and sustainable utilization is imperative. The baseline information generated in this study provides a robust scientific foundation for the formal recognition and registration of Tarai Fowl with ICAR-National Bureau of Animal Genetic Resources (ICAR-NBAGR), Karnal, and serves as a valuable reference for future genetic, genomic, and conservation programmes aimed at promoting climateresilient and sustainable backyard poultry production.

Acknowledgement

AcknowledgementsThe authors gratefully acknowledge the financial and technical support provided by the ICAR-National Bureau of Animal Genetic Resources (ICAR-NBAGR), Karnal, Haryana, under the Network Project on Animal Genetic Resources of West Bengal. The authors sincerely thank the Hon'ble Vice-Chancellor and the Director of Research, Extension and Farm, West Bengal University of Animal and Fishery Sciences (WBUAFS), Kolkata, for providing the necessary facilities and institutional support to carry out this study. The assistance and cooperation extended by the officers and field staff of the Department of Animal Resources Development, Government of West Bengal, including District Animal Resources Development Officers, Veterinary Officers, and Livestock Development Assistants, are gratefully acknowledged. The authors also express their sincere gratitude to the fowl farmers of Alipurduar, Jalpaiguri and Cooch Behar districts of West Bengal for their active participation, generous cooperation, and invaluable traditional knowledge, which were essential for the successful completion of this investigation.

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