Phenotypic and morphometric diversity of indigenous swamp-type buffaloes in the Sylhet wetlands of Bangladesh

Mohammad Mohiuddin¹, Md. Mohan Mia¹, Mohammad Ataur Rahman¹, Md. Nazmul Haque¹, Anik Kumar Kar² and Nayan Bhowmik¹

¹ Department of Genetics and Animal Breeding, Faculty of Veterinary, Animal and Biomedical Sciences, Sylhet Agricultural University, Sylhet, Bangladesh 3100
drnayandvm11@gmail.com
² Department of Digital Anti-aging Healthcare, Graduate School of Inje University, Gimhae 50834, Republic of Korea

Abstract

The domestic water buffalo (Bubalus bubalis) is a vital multipurpose livestock species across Asia, yet its genetic and phenotypic diversity remains underdocumented in many regions of Bangladesh. This study characterized the morphological and morphometric features of local buffaloes in the Sylhet Division to establish a phenotypic baseline for conservation and breeding initiatives. A total of 150 buffaloes (125 cows and 25 bulls) were sampled from 12 sub-districts. Qualitative traits, including coat color, horn type and body pigmentation and 26 quantitative morphometric parameters were recorded and analyzed using descriptive statistics, Chi-square tests, t-tests and correlation analysis. Most animals exhibited dark gray to black coats, black muzzles and crescent-shaped horns oriented upward and inward, consistent with swamp-type buffalo morphology. Significant sex-based differences were found for body length, heart girth, horn length and neck circumference (p<0.05), with cows showing larger dimensions than bulls. Strong positive correlations (r = 0.78–0.86; p<0.01) among major body traits indicated structural proportionality and the potential to predict live weight from simple field measurements. Comparative analysis revealed that Sylhet buffaloes are generally larger than those from other Bangladeshi regions and comparable to Southeast Asian swamp buffaloes, suggesting ecotypic adaptation to humid wetland environments. These findings provide the first comprehensive morphometric description of the Sylhet buffalo population and establish a reference for genetic characterization, conservation planning and sustainable improvement of indigenous buffalo resources in Bangladesh.

Keywords: livestock diversity, morphometry, phenotypic characterization, swamp buffalo

Introduction

The domestic water buffalo (Bubalus bubalis) is a multiservice livestock species of major importance across Asia, valued for draught power, milk, meat and hides and for its adaptability to a wide range of tropical and subtropical environments. The species comprises two main subspecies – river and swamp – that differ in morphology, production potential and traditional uses, together representing a large and diverse global gene pool (Minervino et al 2020). Because of their resilience and multifunctionality, buffaloes contribute substantially to smallholder livelihoods and regional food security in many low- and middle-income countries (Minervino et al 2020).

Globally, water buffalo are distributed across more than 40 countries, but the vast majority of the population is concentrated in Asia. According to FAO data, around 180.7 million buffaloes existed globally in 2008, of which approximately 96.4% (about 175 million) were in Asia, making Asia the dominant centre of buffalo production (Wanapat and Chanthakhoun, 2015). In developing countries, particularly in Asia, buffaloes have historically played a key role in social and agricultural development by providing milk, meat, leather and draught power (Sarwar et al 2009). Their capacity to thrive on low-quality roughages, to operate in wet soils and to perform under low-input conditions underscores their importance to farmers in marginal environments (FAO, 2009).

In Bangladesh, buffaloes remain an important but historically underdeveloped livestock sector. National reviews estimate the buffalo population at about 1.47 million head, mostly indigenous non-descript animals reared primarily for draught and dual-purpose (milk and meat) functions under smallholder and extensive systems (Habib et al 2023; Hamid et al 2016). Buffaloes contribute to rural livelihoods by integrating into traditional crop–livestock systems, providing manure, traction, milk and meat. However, productivity remains low and relatively little systematic breeding or characterization work has been implemented on a national scale (Hamid et al 2016).

The Sylhet region, located in north-eastern Bangladesh, represents a distinctive agro-ecological zone characterized by extensive wetlands (haor areas), marshes and upland pockets that provide heterogeneous grazing resources and seasonal water availability. Buffaloes are commonly kept here under traditional management systems, playing key roles in household income and farm operations. Although local buffaloes in Sylhet are often described as having swamp-type characteristics, published quantitative descriptions of external morphology and morphometric traits for this population are scarce, creating a knowledge gap (Sohel and Amin, 2015).

Phenotypic and morphometric characterization—comprising qualitative traits such as coat color, horn shape and body conformation and quantitative traits such as body length, height and chest girth—is a foundational step in documenting livestock diversity and identifying management-adapted types for future improvement and conservation programs (FAO, 2012; Yeasmin et al 2016). Indigenous livestock breeds are known for their adaptability, disease resistance and efficiency under low-input systems; however, many remain underdocumented and face dilution through unplanned crossbreeding and replacement with exotic germplasm (Köhler-Rollefson et al 2010; Sajjad Khan et al 2007; Vijh et al 2011). Morphometric assessment supports the evaluation of breed structure, facilitates the identification of unique adaptive traits and guides the design of selection or conservation programs (Yeasmin et al 2016).

In Bangladesh, most buffalo populations are non-descript and morphometric characterization studies have been conducted on limited samples in isolated regions such as Mymensingh, Noakhali and Chittagong (Sohel and Amin, 2015; Yeasmin et al 2016). Therefore, a systematic study in Sylhet is warranted. Morphological characterization of buffaloes in this region will serve as a preliminary step toward defining population structure, supporting rational breeding strategies and informing conservation of local buffalo genetic resources, which are at risk of gradual dilution. The present study thus aims to describe the qualitative and quantitative morphological characteristics of local buffaloes in the Sylhet region under traditional management systems and to discuss implications for conservation, utilization and sustainable improvement.

Materials and methods

Study Area

The study was conducted in the Sylhet Division, located in the northeastern region of Bangladesh (Figure 1). The division covers approximately 12,635.22 km² and lies between 23°59′ and 25°13′ N latitude and 90°54′ and 90°30′ E longitude. Sylhet has a humid subtropical climate, characterized by hot, humid summers and relatively cool winters. It falls within the monsoon climatic zone, receiving an average annual rainfall of approximately 3,334 mm, of which about 80% occurs between May and September. The mean maximum temperature reaches around 23°C during August–October, whereas the mean minimum temperature drops to about 7°C in January.

Figure 1. Location of the Sylhet division within Bangladesh (Source: Sufian and Hoque, 2022)

Rainfall in the region has shown variable seasonal trends: summer, critical period and monsoon rainfall have increased by 24.5%, 33.8% and 1.13%, respectively, while winter rainfall has decreased by 35.2%. The rate of seasonal rainfall changes has been estimated at −21.7 mm, 81.7 mm, −6.92 mm and 69.3 mm per decade in winter, summer, critical period and monsoon seasons, respectively (Chowdhury et al 2012). The Sylhet Division encompasses extensive floodplains (locally known as haor areas), marshlands and low-lying agricultural zones, which provide a suitable environment for buffalo rearing under traditional systems.

Sampling design

The Sylhet Division consists of four administrative districts—Sylhet, Sunamganj, Moulvibazar and Habiganj. From each district, three sub-districts (Upazilas) were randomly selected based on the availability of buffalo populations, resulting in a total of 12 sampling sites. A total of 150 buffaloes (125 cows and 25 bulls) were randomly selected following specific inclusion criteria: cows that had experienced at least one parturition and bulls aged 2.5 years or older. We included some bulls younger than 2.5 years in the study because no older bulls were available in some of the selected areas.

Both male and female buffaloes were included to assess physical and morphometric traits. Physical traits recorded included coat color, pigmentation of the forehead, muzzle, hooves, horns, eyelashes, eyes, switch, forelegs, hindlegs and vulva; the presence of pigmentation under the tail; chevron markings on the dewlap; and horn shape and orientation.

Morphometric measurements were taken using a standard measuring tape and measuring stick. They included the following parameters: body length (distance from the point of shoulder to the pin bone), heart girth (body circumference immediately posterior to the forelegs), height at withers and at hip bone, head width (between horns and between eyes), face length (from poll to muzzle), ear length and breadth, horn length and circumference, neck length and circumference, loin, chine and rump lengths, rump and pin bone widths, leg heights (below knee and hock), height and circumference of pasterns, hoof circumference and tail length (from tail drop to tip). A detailed summary of the sampling distribution is presented in Table 1.

Statistical analysis

All collected data on physical and morphometric traits were entered into Microsoft Excel 2013 spreadsheets for coding, validation and cleaning before analysis. To reduce skewness, some categorical traits were grouped or reclassified where appropriate. Descriptive statistics for physical traits were expressed as percentages with 95% confidence intervals and differences between bulls and cows were evaluated using the Chi-square test of independence. Quantitative morphometric traits were presented as mean ± standard error (SE) and comparisons between male and female buffaloes were performed using Student’s t-test. All statistical analyses were conducted using SAS software version 9.4 (SAS Institute Inc., Cary, NC, USA). Statistical significance was considered at p<0.05. The Pearson correlation coefficient was calculated using the rcorr function from the Hmisc package in R (R Core Team, 2025). The correlation plot was created using the corrplot package in R (R Core Team, 2025).

Results

Qualitative (Physical) traits

The qualitative physical characteristics of the local buffalo population in the Sylhet region are summarized in Table 2. The population showed limited sexual dimorphism in most visible traits, with no significant differences between buffalo cows and bulls in coloration patterns, horn shape, or other morphological features (p>0.05, Photo 1). Coat color was predominantly dark gray to black, with minor variations ranging from grayish-black to brownish-gray. Approximately 65.6% of cows and 76.0% of bulls possessed a black switch and both sexes exhibited consistent black pigmentation of the muzzle, hooves and perineal region. Chevron markings were observed in 40.8% of cows and 52.0% of bulls. Horns were generally laterally flattened and oriented upward and inward, with crescent-shaped forms being most common in both sexes, while a minority displayed long scimitar-shaped horns. These morphological features collectively indicate a relatively homogeneous phenotypic pattern characteristic of local swamp-type buffalo populations adapted to tropical lowland environments.

Photo 1. Swamp-type buffaloes in the Sylhet region of Bangladesh. A) Cow; B) Bull

Quantitative morphometric traits

The morphometric characteristics of Sylhet buffaloes (Table 3) showed significant differences in a few key measurements between sexes. Cows exhibited significantly higher mean values for body length, heart girth, and horn length along both curvatures, while having lower mean values for horn circumference at the base and neck circumference when compared to bulls (p<0.05). However, other body dimensions, such as height at withers, height at hip, rump length and limb lengths, did not differ significantly between sexes (p>0.05). These results indicate a general proportional body structure across both sexes, with differences likely attributable to management practices and age composition.

Correlation analyses among 26 morphometric traits (Figure 2) revealed strong positive associations among major body dimensions. Body length, height at withers and heart girth were highly correlated (r = 0.78–0.86; p<0.01), suggesting that animals with greater skeletal length also tend to have broader chest girth and higher stature. Strong relationships were also noted between horn length and head width, indicating coordinated growth of cranial structures. Moderate correlations were observed among limb measurements, including hock and knee lengths, reflecting proportional skeletal development. The presence of strong, positive interrelationships among key body dimensions highlights internal body proportionality in this population. It suggests that body length or heart girth could serve as practical predictors of live body weight for field management purposes.

Figure 2. Pearson’s correlation matrix among morphometric measurements of local buffaloes. Abbreviations: BL = Body length; HW = Height at withers; HH = Height at hip; LL = Loin length; CN = Chine Length; RL = Rump length; HL = Hock length; KL = Knee length; TLS = Tail length up to switch; RW = Rump width; PW = Pin bone width; HP = Height of pastern; HC = Hoof circumference; HG = Heart girth; FL = Face length; EL = Ear length; EB = Ear breadth; NL = Neck length; NC = Neck circumference; HWBH = Width of head between horns; HWBE = Width of head between eyes; HLGC = Horn length along greater curvature; HLSC = Horn length along smaller curvature; HCB = Horn circumference at base; HCM = Horn circumference at middle; HCT = Horn circumference below tip.

Comparative morphometry with Other regional populations

Comparative analysis (Table 4) indicated that Sylhet buffalo cows possessed larger mean heart girth (186.9 cm) and body length (135.6 cm) than those reported for cows from Mymensingh (179.0 cm, 126.2 cm) and Noakhali (131.8 cm, 123.1 cm). Similarly, their hip height (129.4 cm) exceeded the national averages reported in earlier studies. In contrast, Sylhet bulls had slightly shorter body length and heart girth than those in Noakhali, suggesting potential regional variation influenced by local management and environmental conditions. In addition, the smaller body length and heart girth of Sylhet bulls might be due to the inclusion of some younger bulls in the study. The morphometric profile of Sylhet buffaloes aligns closely with that of swamp-type buffaloes in Thailand and Indonesia, whose height, body length and chest girth fall within the same range (Chantalakhana and Bunyavejchewin, 1994; Saputra and Anggraeni, 2023). These findings collectively confirm that the Sylhet population represents a relatively large-bodied, well-proportioned buffalo group with adaptive characteristics suitable for humid wetland ecosystems.

Discussion

Phenotypic traits and adaptation

The predominance of dark coat color observed in Sylhet buffaloes corresponds to the general pigmentation pattern in Asian swamp buffalo populations, where black to dark gray coloration is adaptive for ultraviolet protection in open tropical environments (Soysal et al 2007; Zhang et al 2020). However, dark coats also increase heat absorption, explaining the behavioral tendency of these animals to wallow in water to regulate body temperature (Marai and Haeeb, 2010). The lack of significant sexual dimorphism in coat color and horn shape suggests that these traits are primarily determined by natural selection pressures rather than artificial selection. The consistent occurrence of crescent-shaped horns oriented upward and inward is consistent with the morphological features described in swamp-type buffaloes across Southeast Asia (Chantalakhana and Bunyavejchewin, 1994). Minor occurrences of scimitar-shaped horns likely represent phenotypic variation arising from within-population diversity or limited genetic introgression, as similarly observed in local buffalo pockets of Mymensingh (Sohel and Amin, 2015).

Morphometric traits, correlation patterns and management implications

The morphometric measurements of Sylhet buffaloes indicate a balanced body conformation. Interestingly, the cows show greater body length, heart girth and horn size compared to the bulls. This finding slightly diverges from the general expectation of sexual dimorphism in bovines (Yakubu et al 2009). One possible explanation is that cows are retained for longer periods for milk production and draught work, while males are typically sold or slaughtered at an earlier age. Additionally, the inclusion of some younger bulls may contribute to these findings. The observed high correlations among major morphometric parameters, especially between heart girth and body length, indicate that these traits grow proportionally and can be used as reliable indicators of live body mass (Araújo de Melo et al 2020). The strong correlation between height at withers and body length further confirms the structural harmony of the breed, while moderate correlations among limb traits (e.g., hock and knee lengths) suggest consistent skeletal proportionality. Such high inter-trait correlations have also been reported for indigenous swamp buffaloes of Vietnam and northeastern India (Berthouly et al 2010; Singh et al 2022), where they were interpreted as indicators of phenotypic stability and uniform selection pressure.

Comparative morphometry and ecotype differentiation

Comparative assessment demonstrates that Sylhet buffaloes are generally larger than those from other Bangladeshi regions, including Mymensingh and Noakhali (Siddiquee et al 2010; Yeasmin et al 2016). Their size parameters are similar to those of Thai and Indonesian swamp buffaloes, supporting the classification of the Sylhet population as a local swamp-type ecotype. The larger frame may be attributed to favorable ecological conditions in the Sylhet haor areas, where year-round aquatic vegetation and wallowing opportunities support enhanced growth and condition. Environmental and nutritional factors are well-documented determinants of morphometric variation among buffalo populations (Hamid et al 2016). The strong positive correlations observed among major body traits in this study also imply a high degree of phenotypic integration, which can facilitate effective selection for size improvement without compromising functional balance.

Implications for conservation and breeding

This study provides foundational morphological data that can serve as a reference point for genetic and conservation initiatives targeting indigenous buffaloes in northeastern Bangladesh. The phenotypic uniformity, body proportionality and alignment with swamp-type characteristics indicate that the Sylhet buffalo population possesses valuable adaptive traits that warrant conservation priority. As emphasized by FAO (2012) and Köhler-Rollefson et al (2010), morphological characterization is a crucial preliminary step before molecular and performance-based evaluations. Conservation programs should focus on maintaining the purity of this local gene pool, avoiding unplanned crossbreeding with river-type or exotic breeds and integrating phenotypic markers such as body length, heart girth and horn configuration into selection protocols. The observed trait correlations further suggest that these parameters can be used for rapid phenotypic identification in community-based breeding initiatives.

Conclusions

The present study provides the first detailed morphological and morphometric characterization of the Sylhet buffalo population in northeastern Bangladesh. The animals exhibit uniform dark pigmentation, predominantly crescent-shaped horns and proportional body dimensions that reflect adaptation to wetland agro-ecosystems and traditional low-input husbandry systems. The strong positive correlations among body measurements reveal a consistent structural balance, supporting the use of a limited number of easily measurable traits for field-level assessment. Comparisons with other Bangladeshi and Southeast Asian swamp-type buffaloes confirm that the Sylhet population represents a robust, well-adapted local ecotype. These results establish a valuable baseline for future molecular studies, performance evaluations and conservation planning aimed at preserving and sustainably utilizing this genetic resource.

Acknowledgements

The authors would like to express their gratitude to the Chairman of the Department of Genetics and Animal Breeding at Sylhet Agricultural University, Bangladesh, for providing the essential facilities to conduct this study. We also extend our thanks to Abhijit Chowdhury and Md. Rabiul Islam for their technical assistance and support with sample collection.

Funding

This project was funded by the University Grants Commission (UGC), Bangladesh, through the Sylhet Agricultural University Research System (SAURES), Sylhet Agricultural University, Bangladesh.

Competing interests

The authors declare no competing interests.

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