Phenotypic Characterization of Local Chicken Ecotypes of Benishangul-Gumuz Region, Western Ethiopia

This study was conducted in four districts (Bambassi, Kamashi, Mao-komo and Homosha) of Benishangulgumuz regional state to describe physical and morphological chrematistics of local chicken population in the study area. A total of 847 matured local chickens (619 females and 228 males) were randomly sampled from the study area. Mean live body weight and other linear body measurements of males was significantly (p<0.05) higher than females. The overall mean values of measured traits males of indigenous chicken for body length, wingspan, and height and body weight were 37.0±4.26cm, 22.9±2.72, and 41.9±5.47cm and 1.5±0.413 kg respectively. While the respective values for mature females were 34.0±3.19cm, 21.4±2.72cm, 36.6±2.98cm and1.3±0.32kg. Almost all chickens (91%) in the study area were feathered neck. Regarding the head shape, 81% of the chicken in the study area had plain head shape and the remaining (19%) were crest. Single comb was the most common (82 %) comb type and was predominant in all of the districts. The study revealed that most of the parameters measured revealed distinctive variations, providing the basis for further characterization of local chicken breeds; therefore future study can be concentrated on selection for qualitative traits of interest.

city of Ethiopia. Bambasi is located 45 km East of Assosa town, whereas Kamashi, Homosha and Maokomo are located 225 km North East, 35 km West and 105 km South West of Assosa town, respectively.
Benishangulgumuz regional state is located between geographical coordinates of 9 o 30'N to 11 o 39'N latitude and 34 o 20'E to 36o30'E longitude with altitude ranging from 1272 -1573 masl (AsARC, 2006). Mean annual rainfall and temperature of the region lies between 700 -1450mm and 21 -35 o C, respectively (AMS, 2008). Phenotypic measurements and observations: Linear body measurements and other physical characteristics were measured and observed from 847 chickens, comprising of 228 males and 619 females. The measurement was taken from matured local chicken greater than 6 months of age by asking chicken owners. Measurements were taken early in the morning to avoid the effect of feeding and watering on the chicken size and conformation. Qualitative traits such as plumage colour , body shape, comb type, shank colour, skin colour, head shape, ear lobe colour and eye colour was documented through direct visualization. Whereas measurable traits such as body weight (kg), body length, wing span, shank length, breast circumference, wattle length and width, keel length, beak length, comp length and width, toe to back length, tail length, earlobes length and width and height were measured using spring balance and centimetre (cm) in the nearest two 0.5 digits using breed characterization manual ( FAO,2012). Statistical analysis: SAS, 2008 -program version 9.2 and SPSS (Version_20) were used for all statistical analysis in this study Qualitative Morphological Traits Univariate Analysis: Qualitative morphologic traits were subjected to frequency procedure of SPSS (Version-20).

Quantitative morphological traits
Univariate Analysis: Quantitative morphological traits were subjected to analysis of variance using the general linear model procedure (PROC GLM) of SAS, 2008 version 9.2 to detect statistical differences among sample chicken populations. Duncan's New Multiple Range Test mean comparisons were made for variables showing significant differences between sample populations. Taking districts ecotypes and sex of the chicken as main fixed effects, the following model was used.
Where; The observed linear measurements = Overall mean = Fixed effect of i th district/ecotype (i= 1 Bambassi, 2=Kamashi, 3= Mao-komo, 4 =Homosha) = Fixed effect of j th sex (j= male or female) Fixed effect of interaction of i th district/ecotype with j th sex = random error

Results and discussion Variation in quantitative traits
Least square means ± SD of body weight (kg) and other linear body measurements (cm) for all districts and sex are shown in Table 1. All the quantitative dependent variables were significantly (p<0.05) affected by sex of chickens. The live body weight and other body measurements of this study also showed that male chicken population was significantly higher (P<0.05) than female chicken population in the study areas. This shows the presence of sexual dimorphism in the population. The sexual dimorphism is explained by the differences in level of male sex hormones which is responsible for greater muscle development in males than in females (Jansson et al., 1985).
The mean measured values of body length, back length, wing span, breast circumference and keel length for local adult hens in the study areas were 35.3, 1.5, 22.7, 35.8 and 9.6 cm respectively, with body weight of 1.3kg. The overall mean body weight of adult hens in this study is similar with the study of Eskindir et al. (2013) who reported 1.29 kg for indigenous chicken population of Horro district in East Wellega zone of Oromia region, Ethiopia. But, it is higher than 1.10 kg reported by Addis (2014) for indigenous hens in eastern Amahara region of Ethiopia. However, the study by Addisu et al. (2013) for indigenous chicken population of the same sex in north Gondor zone of Ethiopia indicated higher body weight (1.37 kg) and wing span (36.25 cm). Variation in body weight and other liner body measurements in the present study compared to the literature could be attributed to the ecotype differences among various indigenous chicken populations of Ethiopia.
The mean body weight and body length of local adult cocks in the study area were 1.5 kg and 37.8cm, respectively which are close to body weight of 1.5 kg and body length of 38.0 cm of indigenous chicken population of Horro and Jarso districts of Ethiopia reported by Eskindir et al. , (2013). The study by Addis et al.
(2014) for indigenous cocks in eastern Amahara region of Ethiopia, however, indicated lower value of body weight (1.10 kg) and body length (35.8 cm). But, Halima (2007) reported higher value of body weight (2.02 kg) for adult cocks in Northwest Ethiopia.
In this study, cocks and hens in Kamashi district were found to be significantly higher (P<0.05) in body length, back length, keel length and height compared to the other chicken populations in the study districts. These higher values could be associated with environmental hotness of Kamashi district compared to others as these morphological traits are important for better heat dissipation in the tropical hot environment (Nesheim et al., 1979). abc Means in a row with different superscript letters denote significant differences between populations or sampling districts (p < 0.05) and P D is effect of distrcts, P S is effect of sex, P DS is interaction effect of districts and sex; ,,,,,
Neck feather, head shape, comb type, and earlobe colour Neck feather types, comb types, head shape and earlobe colour of local chickens in the study districts are indicated in Table 3. About 9% of the total chicken populations in the study districts were naked-neck type, though differences were observed among the populations regarding their distribution. Relatively higher proportion of naked-neck chickens were found in Kamash ecotype (13.6%) followed by Mao-komo ecotype (11.2%) than the other two ecotypes. The naked-neck character is described as the expression of a major gene found in local chicken populations of the tropics and is considered to have desirable effects on heat tolerance. Rather rare occurrence of naked-necked chickens might be an indication of a negative selection against this character (Horst, 1989).
Various comb types were observed in the current study where differences in proportion of comb types were manifested among the ecotypes. Single comb was the most dominant (82 %) comb type in all ecotypes. Other comb types (rose, cushion and pea) appeared in small proportion. The occurrence of varieties of different comb types observed in this study might be due to interactions of different genes responsible for comb expression has contended that the heredity of comb type in chickens is attributed to two autosomal pairs of genes RR for Rose type and PP for Pea type) ( Crowford ,1990;Imsland et al., 2012).
The dominant earlobe colours of the ecotypes were red and white (34%) and red colour (29%). This finding is in agreement with previous studies in indigenous chicken ectypes at different parts of Ethiopia (Embet et al., 2014;Tadelle, 2003;Duguma, 2006 andHalima, 2007). Regarding the head shape, 81% of the chickens in the study areas had plain head shape and the remaining (19%) were crest. Figures 1, 2, 3 and 4 show pictures of some plumage characteristics of local chickens appeared in the study areas.

Conclusion
Indigenous chicken population in the study area had distinct physical variations for both qualitative and quantitative traits under traditional management system. This phenotypic variability caused by both genetic and environmental factors. The high phenotypic diversity in indigenous chicken is major evidence for the existence of high genetic variability in the study area. This variability may provide an opportunity for genetic improvement of chicken through selection.