Phenotypic characterization of four indigenous naked neck chicken ecotypes in Pakistan

A study was conducted to characterize four phenotypes (black, white with black tips, light brown and dark brown) of naked neck chickens [n=320; 80(40(cid:0), 40(cid:0))] for qualitative and quantitative traits at 20 weeks of age. Qualitative phenotypic characterization was based on head appearance, comb type, wattle size, plumage pattern, shank color, spurs prevalence and number of toes. Quantitative phenotypic characterization was based on neck length, keel length, shank length, drum stick length, body length, wing span and circumference. Males and females of all phenotype had plain head and single comb. Plain feather pattern was predominantly most frequent on breast, wing bow, wing bar, wing bay, saddle and tail followed by stippled, penciled and laced. Males had most frequent yellow shanks followed by grey, off-white and green. White black, light and dark brown phenotypes expressed maximum yellow shank coloration whereas grey shanks were most frequent in black birds. Morpho-metric measurements were signicantly higher in males than females. Light and dark brown phenotypes had higher values of quantitative traits than those of black and white black. All males and females of naked neck phenotypes possessed four toes, normal spurs and tuft feathers on the ventral portion of the neck above crop. The phenotypic variation observed in indigenous naked neck chickens could provide valuable basic information to develop effective utilization and conservation programs. neck Liyanage nding phenotype neck length, while keel length both in light and dark brown compared to those of other phenotypes. are in accordance with the study of Yakuba et al. (2009) who signicant difference in neck length among different genotype of indigenous Nigerian chickens. ndings also supported by Fadare (2014) signicantly different keel length in Naked-Neck, Frizzled feathered and normal feathered crosses with Exotic Giri-Raja chickens.


Introduction
In developing countries, indigenous poultry is playing important role in poverty alleviation, food security and promotion of gender equality (Gueye 2000). This re ects the potential of this sector which needs to be further exploited by promoting indigenous poultry in the country through various management and genetic tools. Indigenous chickens retain unique adaptive traits that permit them to survive and reproduce under harsh climatic, nutritional and poor management, characteristically related with low input-output production systems (Mwacharo et al. 2007). Global reports suggest that indigenous breeds of livestock are becoming extinct as they cannot economically compete with high yielding commercial breeds (Kiani 2000). In the last decade of 20th century, scientists and livestock owners became worried about the potential loss of native breeds. Due to future changes in climate, management and feeding habits, there is need to collect, evaluate and conserve different genotypes (Crawford 1984). A program was launched for genetic conservation of poultry resources (Scherf 1995). In such scenario, the sustainable management, utilization and conservation of a particular population of domestic animals require its characterization. Phenotypic characterization of available breeds is vital for proper management of these resources. This is a way to classify the individuals on the basis of their morphological and productive trait (FAO 2012), which helps to understand the diversity and distinctiveness of a genetic resource. Due to lack of such information, it is di cult to know about different breeds and their uses. Therefore, phenotypic characterization is of much importance to manage the livestock genetic resources according to their ecological and physiological requirement.
The local chickens vary widely in body size, body conformation, plumage color and many other phenotypic characteristics, which are commonly classi ed worldwide as non-descriptive types due to lack of information (FAO 2012). Non-descriptive local chicken breeds are important source of income and house hold food security in rural farm families (Cabarles et al. 2012). In Pakistan Aseel, Naked neck, Desi and Fayoumi are reared as backyard chickens mainly as a source of high quality animal protein and income. Among these breeds, local Aseel and Naked neck chickens are especially notable for their genetic potential. Naked neck birds are very colorful-black brownish, multicolor, red brownish and black feather combinations (Faruque et al. 2010). This study was designed to phenotypically characterize different varieties of indigenous naked neck chickens for qualitative and quantitative traits as well as productive and reproductive traits, to generate information for advanced conservation genetic studies on native breed of Pakistan.

Methodology
The experimental method was approved by the Ethical Review Committee of the University of Veterinary and Animal Sciences, Lahore-Pakistan.

Location and Meteorological data
The study was conducted at Indigenous Chicken Genetic Resource Centre (ICGRC), Department of Poultry Production, University of Veterinary and Animal Sciences (UVAS), Ravi Campus, Pattoki. Pattoki is located at 31 o 1 , 0 N and 73 o 50 , 60 E with an altitude of 186 m (610 ft). This city experiences normally hot and humid tropical climate with temperature ranging from 05 o C in winter and + 45 0 C in summer.

Bird, s Husbandry
Birds were maintained in an independent open-sided laying housed with the east to west dimension measuring 6.10 × 6.10 m (37.21 m 2 ), equipped with two rows of 3-tiered laying cages measuring 5.18 × 1.52 m (47.42 m 2 ) with sloping wire oor to facilitate egg collection. The ventilation, humidity, and house temperature were controlled using ceiling fans, curtains, and other helpful manual techniques. Variations in daily temperature ( o F) and humidity (%) were noted using a wet and dry bulb hygrometer (Mason's type, Zeal, England) and later an average of the temperature and humidity were derived on weekly basis (FIGURE 1). The removable dropping trays were tted under the mesh oor for the removal of faecal material. Feeding of the birds was done through removable individual trough feeders installed outside the cage and watering through the automatic nipple drinker system tted therein. Birds were offered a commercial laying ration (Table 6) at 06:00 AM with an allowance of 100 g/bird/day and availability of fresh water was ensured with nipple drinking system throughout the experimental period.

Bird, s Population
Three hundred twenty day old naked neck chicks comprising different plumage colors were bought from commercial hatchery Gujranwala, Punjab. Similar managemental and feeding practices were provided for all experimental units. At 20 weeks of age, data of 80 birds (40 males and 40 females) from each plumage group were recorded for seven qualitative traits (head shape, comb type, wattles size, shank color, prevalence of spurs, and number of toes, feather patterns on breast, wing-bow, wing-bar, wing-bay, saddle and tail) and seven quantitative traits (neck length, keel length, shank length, drum stick length, body length, wing span and circumference), as per the method described by Cuesta (2008) and Amjad et al. (2015) and the patterns on the feathers were compared against the British Poultry Standards (Roberts 2008). The qualitative traits for each chicken were scored visually, while the quantitative traits were measured in centimeters using a measuring tape and Vernier caliper (0.01 mm). All measurements were taken by the same person to avoid individual variation during observation.

Statistical Analysis
Data on qualitative traits were analyzed with descriptive statistics as percentages, while data on quantitative traits were analyzed by one-way analysis of variance, followed by Duncan's multiple range test to test signi cant differences between means (P<0.05).

Plumage Patterns on Breast, Wing Bow, and Wing Bar
The results of present study regarding feather patterns on breast, wing bow, wing bar, wing bay, saddle and tail in different phenotypes of naked neck chickens are shown in Table 1. Breast plumage pattern showed variation in sex and phenotypes. Mostly females expressed plain feather pattern followed by stipple, single laced, penciled and double laced. Stippled feather pattern was dominant on breast in male than plain. As concern of phenotype, black had higher coverage of stippled feather followed by plain. White with black phenotype birds had maximum plain feather pattern as compared to other phenotypes. Light brown birds had both plain and stippled feather pattern in higher ratio followed by penciled and laced. The breast of dark brown birds had also higher ratio of plain and stippled feathers.

Plumage Patterns on Wing Bay, Saddle and Tail
Variations on wing-bay feather pattern in different phenotypes of naked neck birds were noted. Black phenotype expressed plain pattern (36%), stippled (32%), laced (19%) and penciled (13%), white black had plain feather pattern (70%), penciled (12%), stippled (10%) and laced (8%), light brown had (60%) plain, (24%) stippled ,(9%) penciled and (7% ) laced feather pattern and dark brown expressed (58%) plain feather pattern, (17%) stippled, (13%) laced and (12%) penciled, respectively. Sex, phenotypes and their interaction displayed differences in arrangement of feather on saddle. Males had maximum plain feather pattern succeeded by stippled, penciled and single laced. Females also had higher range of plain feathers followed by stippled, single laced and penciled. As the phenotypes pattern arrangement concerned, white black, dark brown and light brown phenotypes showed maximum range of plain feathers followed by stippled, penciled and laced whereas black phenotype had higher stippled feathered pattern on tail followed by plain, penciled and laced. White black female had maximum plain feathered pattern whereas light brown males expressed maximum stippled feather patterns compared to other phenotypes and sex. Black females expressed high single and double lacing as compared to other phenotypes and sex. Dark brown males showed maximum penciled pattern compared to other competitor phenotype and sex ( Table 2).
Both sex and phenotypes showed variations in tail feather pattern. Over all, females had maximum plain, penciled and single laced as well as double laced feather patterns as compared to males, while males expressed higher percentage of stippled feather pattern. As concerned phenotypes, plain and penciled feather pattern was dominant in white black compared to those of other phenotypes. Stippled pattern was mostly expressed in light brown followed by dark brown, black and white black phenotypes. Double laced feather pattern was frequent in dark brown while single laced was in black phenotype with respect to other competitor phenotypes. Maximum single laced pattern was observed in feathers of black females, double laced in dark brown females. Plain pattern percentage was higher in white black males and light brown females. Stippled pattern was noticed maximum in feathers of light brown males. Maximum penciled pattern was recorded in feathers of white black females (Table 3).

Shank Color
The results of the present study with respect to the shank color revealed signi cant differences in both sex and phenotypes. Yellow shanks were predominantly most common in males followed by grey and off-white shanks ( Table 4).

Neck and Keel Length
In the present study, both sex and phenotypes were signi cantly different in terms of neck and keel length. Males had higher neck and keel length than females. Light brown phenotype expressed higher neck length while keel length was higher both in light and dark brown compared to those of other phenotypes (Table 5). In sex and phenotype interaction, light brown male showed higher neck length; however, keel length was maximum both in light and dark brown males.

Wing Span, Shank Length And Circumference
The mentioned morpho-metric traits demonstrated signi cant differences in sex, phenotype and their interaction. Males had greater wing span, shank length and shank circumference as compared to females. Wing span and shank length were observed signi cantly higher in dark brown males as compared to those of other phenotypes, while males of all phenotypes had no difference in shank circumference ( Table 5). The mentioned morpho-metric traits demonstrated signi cant differences in sex, phenotype and their interaction. Males had greater wing span, shank length and shank circumference as compared to females. Both light and dark brown phenotypes had higher wing span and shank length whereas there was no difference in shank circumference among various phenotypes. In interaction, wing span and shank length were observed signi cantly higher in dark brown males as compared to those of other phenotypes, while males of all phenotypes had no difference in shank circumference (Table 5).

Body Length, Drum Stick Length And Circumference
Signi cant differences were observed in sex, phenotypes and interaction regarding above stated quantitative morpho-metric traits. Males had signi cantly longer body and drum stick length as well as more circumference than females (Table 5). Phenotypes had no variation regarding drum stick length, while circumference was signi cantly higher in dark brown, though body length was longer in light brown phenotype. It was observed that there is no difference in drumstick length among males of all phenotypes, however, circumference was higher in dark brown male and body length was in light brown male. In the present study, black phenotype naked neck had small sized wattle (56%), followed by medium (34%), very small (8%) and large (2%). White black phenotype had medium sized wattles (51%) followed by small (26%), large (14%) and very small (9%); light brown naked neck chickens had medium sized wattles (73%) followed by small (16%), large (9%) and very small (2%). These ndings are in agreement with those of Roberts (2008) who illustrated medium sized wattles in Transylvanian naked neck chickens. Dark brown phenotype had wattle size as; medium (68%), small (19%), large (10%) and very small (3%). Amjad et al. (2015) also reported most frequent medium sized wattles in naked neck ecotype of Pakistan. In the present study, as mentioned above, mostly females expressed plain feather pattern followed by stipple, single laced, penciled and double laced. Iqbal et al. (2015) observed that mostly naked neck birds had plain feathered pattern, which is in accordance with our ndings. Syakir (2018) and In the present study, yellow shanks were predominantly most common in males followed by grey and off-white shanks. In line with these results,  2021), likewise, observed that the most common shank color was yellow (35.29% in males and 37.36% in females), followed by gray-green, black, white, green, black-white, and black-yellow green. Yellow shank coloration was found to be higher in dark brown phenotype, off-white shank color was higher in white black, grey and green shank color was higher in black phenotype. White black males had maximum yellow and off-white shank coloration and black females were higher in grey and green shank coloration. Similar to these ndings, In the present study, males had signi cantly longer body and drum stick length as well as more circumference than females. Similar to our ndings, Dorji & Sunar (2014) Table 4 Comparative shank color percentage in males, females and four Phenotypes of naked neck chicken and their interaction (Sex × Phenotype).   Figure 1 Variations in temperature (oF) and humidity (%) by a wet and dry bulb hygrometer (Mason's type, Zeal, England).