On-Farm Phenotypic Characterization of Indigenous Sheep Types in Selale Area, Central Ethiopia

Ethiopia is endowed with huge livestock resources of varied and diversified genetic pools with specific adaptations to a wide range of agro-ecologies. Farm animals as a whole are an integral part of the country’s agricultural system and are raised both in the highland and lowland areas. In developing countries, livestock production is mostly subsistence oriented and fulfills multiple functions that contribute more for food security [1,2]. The demand for livestock products is increasing due to the growing urban population, while farm areas are shrinking considerably as a result of an increase in the rural population [3].


Introduction
Ethiopia is endowed with huge livestock resources of varied and diversified genetic pools with specific adaptations to a wide range of agro-ecologies. Farm animals as a whole are an integral part of the country's agricultural system and are raised both in the highland and lowland areas. In developing countries, livestock production is mostly subsistence oriented and fulfills multiple functions that contribute more for food security [1,2]. The demand for livestock products is increasing due to the growing urban population, while farm areas are shrinking considerably as a result of an increase in the rural population [3].
Ethiopia is home for at least 9 breeds and 14 traditional sheep populations [4] with an estimated 25.9 million heads. Out of which about 73.1 percent are females, and about 26.9 percent are males [5]. Of the total sheep population, 75 percent is found in the highlands where mixed crop-livestock systems dominate, while the remaining 25 per cent of the sheep is found in the lowlands [6]. The main production from indigenous sheep populations in Selale area is meat, skin and manure.For planning of community based breeding strategy as well as setting up a useful sheep development program, the genetic and the phenotypic merit and production system of that particular breed is a must. It has been stressed that identification and characterization of livestock genetic resources and their production environment is vital for long-term genetic improvement and sustained use of available resources [7].
On farm characterization can serve as basis for the sustainable improvement and conservation of indigenous animal genetic resources, and has received increasing attention in determining the variation between and within pure breeds [8]. Thus, more comprehensive information specific to on-farm phenotypic characterization of indigenous sheep breeding should be made available. Hence, this study was attempted to physically characterize indigenous sheep types in Selale area, Central Ethiopia.

Study area
The study was conducted in Selale area, Debre Libanos and Wuchale district, central Ethiopia. Debre Libanos and Wuchale district are located at 85 km and 75 km north of the capital Addis Ababa, respectively. Debre Libanos is located in 38 o 58' 33"E longitude and 9 o 63' 75''N latitude with altitude ranging from 1500 to 2700 m.a.s.l. For Debre Libanos the maximum and minimum annual temperature is 23 0 C and 15 0 C, respectively. Its main rainy season occurs between May and September and the dry season lasts from October to April. Wuchale district is located in 38 o 47'E longitude and 9 o 54'N latitude with maximum temperature of 25 0 C and minimum of 3 0 C. Similarly, the main rainy season of Wuchale district occurs between May and September and the dry season lasts from October to April. Clay and sandy soils are the major soil types of the zone. In both of the districts agricultural production is characterized by a mixed crop-livestock production system [9] (Figure 1).

Sampling procedure
Selection of the studied districts and peasant associations were done using multi-stage purposive sampling technique in consultation with zonal and district bureau of agriculture experts. Four Kebeles in Debre Libanos (Wakene, Sone, Dire Jibbo and Tere) and four Kebeles in Wuchale district (Jate, Harkiso, Adere Gordoma and Gora Keteba) were selected based on their suitability for sheep production, road access and willingness of the farmers to participate in the study. A total of 400 female (200 in Debre Libanos and 200 in Wuchale) and 160 male (80 in Debre Libanos and 80 in Wuchale) sheep were selected for body linear measurements.

Data collection
The standard breed descriptor list for sheep developed by FAO [10] was closely followed in selecting morphological variables. Qualitative traits like: coat color pattern, coat color type, hair type, head profile, ears, wattle, horn, ruff and tail were observed and recorded. Body measurements: Chest Girth (CG), Body Length (BL), Wither Height (WH), Rump width (RW), Ear Length (EL), Horn Length (HL), Tail Length (TL), Tail width (TW), Rump length (RL) and Scrotum circumference (SC) were measured using flexible measuring tape while weight was measured using suspended spring balance having 50kg capacity with 0.2kg precision. Each experimental animal was identified by sex, districts and age group. Adult sheep were classified into three age groups; 0PPI (zero pair of permanent incisor), 1PPI (one pair of permanent incisor) and 2PPI (two pair of permanent incisor. Linear body measurements were taken by restraining and holding the animals in a stable condition.

Data management and analysis
Statistical analyses were made separately for male and female animals on variables that varied on sex; otherwise the data were merged and analyzed together. Qualitative data from individual observation were analyzed following the frequency procedures of SAS version 9.1(2005). The General Linear Model (GLM) procedure of SAS was employed to analyze quantitative variables to determine effects of class variables (sex, district and dentition). The effects of class variables and their interaction were expressed as Least Square Means (LSM) ± SE. Due to the low number of males in each dentition class, analysis was done for both sexes independently. Within each sex, location and dentition were fitted as fixed factors. Pearson's correlation coefficient between linear bodies measurements under consideration were computed for both of the sheep types within each sex.

Univariate and multivariate analysis
General linear model procedures (PROC GLM) of the SAS were employed for quantitative variables to detect statistical differences among sample sheep populations. Mean comparisons were made for variables showing significant differences between sample populations. The quantitative variables from female and male animals were separately subjected to discriminant analysis (PROC DISCRIM of SAS) and canonical discriminant analysis (CAN DISC) programme to ascertain the existence of population level phenotypic differences among the sample sheep populations in the study area.

Characterization of qualitative traits
The major qualitative traits of sample sheep population are presented in Table 1. Out of the sampled 390 sample sheep, 58.21 % were plain, 33.33% patchy and 8.46% had spotted coat pattern. Brown and white with brown dominant (24.87 %), brown with red dominant (16.92%), and white with black dominant (19.23%) coat color patterns were the dominant colors. Beside, brown (18.21%), black (4.36%), white (4.87%) and red (6.67%) coat were also observed in plain pattern and mixed in patchy or spotted patterns.
Majority of sheep population (80.77%) didn't have toggle and majority (82.05%) lack ruff. Ear formation of sheep population was carried semi-pendulous (86.67%) followed by rudimentary (13.33%). Females were usually polled (74.84%) with 48.72% straight concerning horn shape. Males were characterized by curved horn shape (74.29%) and spiral horn shape (25.71%) in Debre Libanos while 52% and 48% in Wuchale district, respectively. In 67.10% of the female population the tail was straight down pointed while the rest 32.90% had twisted tail. In contrary to the female sheep population male had straight with twisted end (65.71%) while the rest (34.29%) straight with tip down ward. districts had tails hanging straight downwards and 40.26 % of them had twisted end. The higher proportion of male sheep with long and straight downward pointed tail might be due to selection against twisted end tail animals and farmers preferences of straight downward pointed tail. It was noted that ruff was mainly sex and age dependent. They were totally absent in females and more readily observed in adult males as compared to young growing males. The chi-square testfor assumption of equal proportion of categorical variables in both Wuchale and Debre Libanos sample sheep population indicated that among the variables considered in this study coat pattern, coat color, toggle, tail type, tail conformation and ear form were found to significantly (P<0.05) differ within the sample sheep population.

Live body weight and linear measurements
The body weight and linear measurements for Debre Libanos and Wuchale sheep population at various ages are presented in Table 2. Least squares means of most of the quantitative variables were significant (P<0.05) between districts except body weight and Scrotal circumferences (Table 2). Results for body weight and linear measurements of Debre Libanos and Wuchale sheep revealed that Debre Libanos had significantly larger (P<0.05) linear measurements than Wuchale sheep population.
Sex by age group: The interaction between sex and age group not significantly (p>0.05) affect ear length of the sheep. The remaining parameters of body measurements were affected by the sex-age interaction effect. Both females and males in age group 0(0PPI) had the same (p>0.05) body weight value but males in age group 1(1PPI) and ≥ 2PPI were heavier (p<0.05) than females in the same age group. Body weight of males in age group 0PPI (25.7 ± 0.3kg), age group 1PPI (31.9 ± 0.8kg) and age group ≥ 2PPI (38.2 ± 2.0kg) in the current study was higher than body weight of Menz males18.0 ± 0.28kg, (22.9 ± 0.39kg) and24.9 ± 0.67 in the same age group. Similarly, body weight of females in all age group in the current study was higher than the values reported for Menz ewes (19.1 ± 0.27kg) in the same age group [11].    Age by location:The interaction of age group and location was significant (p<0.05) for all parameters of body measurement used in the study. The result indicates the interaction of age group and location had strong effect on body weight and linear body measurements. Young (0PPI) sheep of DebreLibanos had similar (p>0.05) body weight with Wuchale sheep. The age group ≥ 2PPI also had similar (p>0.05) body weight 2 locations. However, Wuchale sheep (28.8 ± 0.7 kg) in age group 1PPI had heavier body weight than Debre Libanos (26.7 ± 0.7 kg). This implies that Debre Libanos sheep did not attain maturity at 2PPI. Body weight of the age group 1PPI of the two locations is larger than Tocha, Mareka and Konta sheep [12] and Menz sheep [11] in the same age groups.

Correlation between body weight and body measurements
The highest relationship between chest girth and body weight were observed in Debre Libanos female sheep (0.68) and in Wuchale male sheep (0.80).The highest correlation of chest girth with body weight than other body measurements was in harmony with other results of [11,[13][14][15]and it can indicate that chest girth is the best variable for predicting live weight than other measurements (Table 3).
Of the linear body measurements, chest girth with exception in Wuchale females had the highest correlation with body weight at all groups. In both Wuchale and Debre Libanos districts, the highest correlation coefficient between body weight andchest girth, body length, wither height and rump height were established in males (73%, 53%, 62%, 64%) for Debre Libanos and (80%, 73%, 72%, 75%) for Wuchale. The highest positive and significant correlation between body weight and chest girthsuggest thatthis variables couldprovide a good estimate for predicting live weight of these breed types (Table 4).    Small AIC, Cp and BIC value and higher adjusted R 2 are included in regression equation. The independent variables were body length, chest girth; wither height, rump height, rump width, tail length, tail width and rump length. In addition to these variables scrotal circumference and horn length were considered for male population.In most cases heart girth was found to be the most important in accounting sizeable proportion of the changes in the body weight. Similarly, this measurement was reported for Afar, Menz, Bonga, Horro, Gumuz, Jarso, and Nedjo sheep [11,[16][17][18]. Chest girth was more reliable in predicting body weight than other linear body measurements. Parameter estimates in multiple linear regression model showed that higher R 2 adjusted was observed when more than one body dimensions were used in the multiple regression equation.

Conclusion
The present study conducted in Selale area of Central Ethiopia evidenced that most of the sheep in the study area had plain coat pattern, brown coat color, semi-pendulous ear orientation and long fat tailed with straight down pointed in females and twisted end in males. Sex of the sheep had no significant (p>0.05) effect on the body weight, ear length and rump length. Age group had significant effect (p<0.05) on body weight and other body measurements. Location was found to influence (P<0.05) body length, tail width, wither height, ear length and rump length. The interaction of sex and age group significantly (p<0.05) influenced all linear body measurements except ear length of the sheep. The interaction of age group and location was significant (p<0.05) for all linear body measurements. Of the linear body measurements, chest girth with exception in Wuchale females had the highest correlation with body weight at all groups. In the regression analysis carried out to predict body weight, heart girth was selected and explained more variation than other variables in all age groups of both males and females of Debre Libanos and Wuchale sheep population. For any breed improvement program and to boost productivity of indigenous sheep, characterization is the baseline. Therefore, this preliminary work could be used to support genetic analyses to determine variation between and within these small populations.