Growth and Physical Body Characteristics of Gumuz Sheep under Traditional Management Systems in Amhara Regional State, Ethiopia

S Abegaz, B P Hegde* and M Taye**

Gondar Agricultural Research Center, P.O.Box 1337, Gondar, Ethiopia
* Haremaya University, P.O.Box 287, Haramaya, Ethiopia
** Bahir Dar University, College of Agriculture and Environmental Sciences, P.O.Box 830, Bahir Dar, Ethiopia
mengistietaye@yahoo.com

Abstract

A study to characterize Gumuz sheep breed was conducted at Metema district of the Amhara National Regional State, Ethiopia. Farmers in Metema area rear different breeds of sheep such as Gumuz, Rutana and highland sheep, in combination as well as sole. However, most (68.9%) rear Gumuz sheep alone. The flock size for only Gumuz sheep rearing farmers was 13.2 heads of sheep. Gumuz sheep is a thin tailed short haired sheep. The most common coat color pattern in both male and female sheep was plain (47.7%; 60% in males and 41% in females) with varying colours. White coat colour was common followed by mixture of red-brown with white in males while the mixture of red-brown with white was the dominant colour in females. Most sheep (93%) had convex head profile. Wattle and horn were only present on 2.9% and 13.8 (only on males), respectively. Most (63.8%) of the males had ruff. They had long and semi pendulous ears. The mean mature body weight (kg) obtained was 31.4 and 34.6 for females and males, respectively. The average body length (cm) obtained were 67.0 and 68.3, height at wither (cm) were 63.6 and 67.3and chest girth (cm) were 76.1 and 78.0 for mature females and males, respectively. The average birth weight, one month weight and adjusted weaning weight were 2.79±0.03 kg, 6.57±0.18 kg and 12.5±0.23 kg, respectively. Birth weight was significantly affected by parity of the dam, type of birth and sex of lamb. Weaning weight was affected by sex of lamb only. The growth curve fitted depicts that Gumuz sheep attained their mature weight around 1 and 1.5 years of age. In general, Gumuz sheep is one of the most important sheep breeds with better body size and growth performance adapted to the harsh climatic conditions of the country. Efforts that could make wise utilization of this genetic resource should be acknowledged.

Key words: Metema district, Pastoral production systems, Rutana sheep, thin tailed sheep

Introduction

Ethiopia, with its divers agro-climatic zones which help to harbor different livestock species and breeds, has a large number of sheep breeds (Gizaw et al 2007) and sheep populations (21 million heads) (CSA 2006). The sheep population is widely distributed from the cool alpine climate of the mountainous highlands to the arid pastoral areas of the lowlands (DAGRIS 2003; Gizaw et al 2007).

Sheep types in Ethiopia are highly affiliated to specific ethnic communities. Several traditional breeds are reared by and named after specific communities. Some communities attach special cultural values to their sheep and exclude use of breeding stock from other populations, resulting in cultural barrier to gene flow (Gizaw et al 2007). Gumuz sheep, after the name of the ethnic group keeping them, is the only thin-tailed sheep in Ethiopia which is confined to the western lowlands bordering the Sudan through which thin-tailed sheep were believed to be introduced into East Africa (Gizaw et al 2007).

Gumuz sheep have evolved under the hot to warm, moist and sub-moist tropical climate at an altitude of 400 to 1400 m a.s.l (Sisay 2002). It has good adaptation to the harsh environmental conditions of the area. Pastoralists and agro pastoralists keeping this breed of sheep, however, are crossing the breed with Rutana sheep (sheep breed from the Sudan) with out bothering about the genetic merit of the breed (Personal observation). Considering this, the sustainable natural resource development and utilization program, an Austria-sponsored program operating in Metema Woreda, North Gonder Zone of the Amhara State, is on the way to establish a new Gumuz sheep breeding center to prevent the breed from extinction due to unwise utilization (ENA 2010).

Conservation and utilization of animal genetic resources needs appropriate description of the production system and the breed of interest. Production system survey and monitoring of Gumuz sheep flock was conducted in the Gumuz sheep production area. The objective of this paper was to describe the general morphology and growth performance of the Gumuz sheep breed under on-farm management conditions.

Materials and Methods

Study area description

The study was conducted in Metema district of the Amhara National Regional State, located about 900 km northwest of Addis Ababa and about 180 km west of Gondar town. The district lies between an altitude ranges of 550 to 1608 m a.s.l. The mean annual temperature ranged between 22^oC and 28^oC. Daily temperature is very high during the months of March to May, when it may get as high as 43^oC. The mean annual rainfall of the area ranges from about 850 to 1100 mm. Metema has uni-modal rainfall. The rainy months extends from June to the end of September. However, most of the rainfall is received during the months of July and August (IPMS 2005). The natural vegetation is predominantly composed of different acacia species with a lot of hyparrhenia grass under grown. Metema is one of the districts where gum and incense is collected. The main species for incense production is Boswellia papyrifera, while Acacia seyal and A. polyacantha are used for gum production (IPMS 2005).

Data collection 

A questionnaire survey and flock monitoring was conducted to characterize the production system and the morphological characteristics of Gumuz sheep. For the survey, three peasant associations (PAs) (Shinfa, Kokit and Kumer-Aftit) that are known for keeping Gumuz sheep were purposely selected. A total of 135 farmers; 60, 55 and 20 from Shinfa, Kokit and Kumer-Aftit were selected, respectively. This was because of uneven distribution of sheep populations in the study PAs. Each flock owner was interviewed to get information regarding breed of sheep reared, sheep management practices, average holding and flock structure of sheep.

Among the flocks used in the survey, only those keeping only Gumuz sheep were selected for monitoring. A total of 27 Gumuz sheep flocks were randomly selected and ear tagged and monitored for about four months (from September 2006 to January 2007). During monitoring, information on growth (birth weight, weaning weight and mature weight) and reproductive parameters (birth type) were recorded by a trained enumerator on the site. Birth weight was taken with in 24 hrs of lambing. Growth data were taken every 15 days using Salter balance (50 kg capacity with 200 gram precision) for lambs below six months of age and monthly for those above six months old.

For morphological characteristics, both qualitative and quantitative characters were collected on 172 (114 females and 58 males) mature animals (animals with one pair of permanent incisors (PPI) and above). Age was estimated using dentition. The animals used for characterization were assumed to be true to breed type. FAO (1986) breed description list was used for the characterization. 

Qualitative characters collected were color, head profile, presence or absence of wattle, presence or absence horn, presence or absence beard, tail type and presence or absence ruff.

Linear body measurements such as: Chest Girth (CG) -the circumference of the chest posterior to the forelegs at right angles to the body axis; Body Length (BL) – horizontal length from the point of shoulder to the pin bone; Height at Wither (HW)– the highest point measured as the vertical distance from the top of the shoulder to the ground (bottom of forelegs); Ear Length (EL) – length of the external ear from its root to the tip; Tail Length (TL)- from the point of attachment to the tip; and Horn Length - from the base of the horn at the skull along the dorsal surface to the tip of the horn were measured. All the measurements were taken using flexible metal tape (3 meter length) to the nearest 0.5 cm after restraining and holding the animals in an unforced position.

Statistical analysis 

The descriptive statistics procedure of the Statistical Package for Social Sciences (SPSS, 2003) was used to describe the morphological characteristics and linear body measurements. For the analysis of variance of fixed effects on growth of lambs and growth curve, the General Linear Model procedures (SPSS, 2003) were used.

For growth of lambs, the fixed effects considered were parity of dam, sex of lamb and type of birth and, age at weighing was considered as a covariate for one month and three months weight. The statistical model used to analyze growth was:

Y_ijkl = μ + P_i + S_j + T_k + b (Wtage_ijk- Wtage) + e_ijkl

Where: Y_ijkl = the observation on birth weight, weight at one and three months of age; μ = Overall mean; P_i = Fixed effect of parity of the dam (i = 1, 2, …,>5); S_j = Fixed effect of sex of lamb (j = male, female); T_k = Fixed effect of birth type (k = single, twin); b = Linear regrerssion of weighing age on one and three month weights; e_ijkl = effect of random error.

The statistical model used to analyze growth curve was:

Y_ijk = μ + S_i + A_j + (SA)_ij + e_ijk

Where: Y_ijk = the observation on body weight at different ages; μ = Overall mean; S_i = Fixed effect of Sex of the animal; A_j = Fixed effect of age of animal; (SA)_ij = the interaction between sex and age of the animal; e_ijk = effect of random error.

Results and discussion

Flock management

Herding management was different between farmers. Some herd sheep lonely (23%) while others herd with goats (47.4%). There were some who do not herd sheep (29.6%); they freed sheep to roam by them selves.

The main feed sources for sheep in the area were natural pasture, crop residue, crop after math and hay. Natural pasture was the major feed resource. As opposed to others areas of the country to which feed is the major production problem (Mengistie et al 2010; Tesfaye 2008), feed shortage was not production constraint in the study area. The only crop residue used as feed is sorghum Stover. The crop residues of other crop (sesame and cotton) are not suitable feed for sheep and other livestock species. Most farmers supplement their sheep during the dry season. The major supplementary feeds were sesame cake, sorghum grain and local brewery by-product (atela). There was also supplementation of common salt usually during the wet season.

Sheep had night time housing using shelter constructed only for sheep (36.3%), in the main house together with the family (9.6%), or enclosure in the compound (54.4%).

Reproduction was uncontrolled; rams run with ewes throughout the year. During lambing, the ewes with their young were kept in the house for one day after that the ewes join the flock for grazing. However, newly born lambs continued to be kept at home for about a week after which they join the flock.

Flock size and demography

Flock in the present study was defined as a group of sheep kept and owned by a farmer. The flock sizes and structure of Gumuz sheep is presented in Table 1. Farmers in the study area keep different breeds of sheep. About, 68.9%, 25.2 % and 5.2 % of the farmers kept Gumuz sheep only, Gumuz & Rutana, and Gumuz, Rutana & Dega sheep, respectively. The farmers maintained genetically diverse sheep breeds and varied composition of flock to match the local environmental conditions. Gumuz sheep was found to be most preferable breed type in the area. Farmers preferred this breed because of its adaptation to the harsh climate, fast growth and better twining rate.

The average flock size obtained, for all flocks including those having Rutana and Dega sheep, in the present study was 16.02sheep per flock. The flock size for those having only Gumuz sheep was 13.2 heads of sheep.  A similar result was reported for highland sheep in Lallo Mama Midir in the central highlands of Ethiopia (Abebe 1999). However, the figure is larger than the sheep flocks in the mixed crop livestock production system of Ethiopia (Mengistie et al 2010; Tsedeke 2007).

Flock structure based on estimated age groups calculated for Gumuz sheep was 49.8%, 7.23%, 8.84%, 7.23% and 26.91%for ewes, rams, ewe lambs, ram lambs and lambs, respectively. The proportion of ewes (mature ewes and replacement ewe lambs) was higher (58.63%) from other groups. Even though the proportion of rams and ram lambs was low, the ram to ewe ratio was 1:7. A ram to ewe ratio of 1:30-60 is satisfactory to ensure efficient conception rate (Gatenby and Humbert 1991) and thus, in Gumuz flock ratio of male to female is more than enough.

Physical body characteristics

The physical body characteristics of Gumuz sheep is presented in Table 2. Pictures showing Gumuz sheep are presented in Figures 1, 2 and 3.

Gumuz sheep is a thin tailed sheep with varying coat color. The most common coat color pattern in both male and female sheep was plain (47.7%; 60% in males and 41% in females).There was various types of coat color in Gumuz sheep. White coat colour was common followed by mixture of red-brown with white in males while the mixture of red-brown with white was the dominant colour in females. Most sheep (93%) had convex head profile. Wattle and horn were rare; only present on 2.9% and 13.8% (only on males), respectively. Most (63.8%) of the males have ruff. They have long and semi pendulous ears.

Figure 1. Gumuz ewe (left) and Gumuz ram (right)

Figure 2. Flock of sheep coming back to home from grazing	Figure 3. A flock of sheep belonging to a farmer in a village

Linear body measurements

 Physical linear body measurements of mature Gumuz sheep were analyzed for sexes separately and are presented in Table 3. The mean mature body weight obtained (31.4 and 34.6 kg for females and males, respectively) was higher than the average body weight of central highland sheep, Rift Valley sheep and Menz sheep in Amhara regional state (Sisay 2002; Tibbo et al 2004) and compares with Washera sheep of north-western highland (Mengistie et al 2010) and Horro sheep (Tibbo et al 2004).

Gumuz sheep were longer in body length as compared to central highland, Rift valley and north-western highland sheep (Sisay 2002). The chest girth obtained also was higher as compared to central highland and Rift Valley sheep (Sisay 2002).

Growth performances of Gumuz sheep

Factors affecting body weight of lambs at different ages is presented in Table 4. The overall least squares mean birth weight obtained was 2.79±0.03 kg. Similar values were reported for birth weight of Washera sheep (Mengistie et al 2009), Afar sheep (Yacob 2008) and Horro sheep (Abegaz et al 2002). However, it is larger than the values reported for Menz sheep (Tibbo 2006; Gizaw 2002; Kassahun 2000).

Parity of the dam affected (P<0.001) birth weight of lambs; dams with higher parities lambed heavier lambs. Many scholars reported a similar result (Mengistie et al 2009; Duguma et al 2002; Gardner et al 2007). This might be because the reproductive organs of first parity ewes are less developed to bear large fetus in which the physiology adjusts the fetal size (Tibbo 2006). Indeed, younger ewes were still growing, and there would have been a competition for nutrients between the fetus and the dam (Duguma et al 2002).

Male lambs were heavier (P<0.001) at birth (2.86±0.04 vs. 2.67±0.03). This is in agreement with literature (Kassahun 2000; Duguma et al 2002; Hassen et al 2004; Benyi et al 2006; Tibbo 2006; Gardner et al 2007; Mishra et al 2007; Yilmaz et al 2007; Thiruvenkadan et al 2008; Mengistie et al 2009).

Similarly, type of birth affected birth weight that single born lambs weigh heavier (P<0.001) than twin born lambs. This could be because of the finite capacity of the maternal uterine space to gestate offspring (Gardner et al 2007), as litter size increases individual birth weights decline. The resultagreeswithliterature (Mourad et al 2001; Rastogi 2001; Duguma et al 2002; Benyi et al 2006; Tibbo 2006; Gardner et al 2007; Mishra et al 2007; Yilmaz et al 2007; Mengistie et al 2009).

The overall least square three months weight (weaning weight) obtained in this study (12.5±0.23, kg) was almost similar with the report of Mengistie et al (2009) for Washera sheep in the western highlands and Horro sheep (Abegaz et al 2002). However, Gumuz lambs were heavier than Menz sheep (Kassahun 2000; Hassen et al 2002; Tibbo et al 2004) and Horro sheep (Kassahun 2000; Tibbo et al 2004) at 3 months.

Among the fixed effects considered, only sex of lamb had a significant effect on weight at three months of age of Gumuz sheep. Males were heavier than their female contemporaries (13.15±0.30 vs. 11.88±0.31). Similar observation was reported in literature (Duguma et al 2002; Tibbo 2006; Yilmaz et al 2007).

 Growth curve of Gumuz sheep

The growth curve of Gumuz sheep, presented in Table 5 and Figure 4, was fitted using the estimated age (dentition class) and weight (during monitoring). The growth of sheep at early age (age groups 1 and 2; up to one year of age) was fast declining after the first milk tooth was erupted (third age group; about one year of age). There was no significant difference in weights of sheep for age groups above one pairs of permanent incisor (above 13 months of age). Thus, Gumuz sheep attained their mature weight around 1 and 1.5 years of age. This finding draws support from the report of Sisay (2002) on the thin tailed sheep which was said to attain the mature weight starting from two permanent teeth.

Figure 4. Growth curve of Gumuz sheep

Conclusions and Recommendations

• Gumuz sheep is the only identified thin tailed sheep breed in Ethiopia. The breed has its own identifiable morphological characteristics.

  
  

• The compararable productivity of Gumuz sheep with other sheep breeds in the country under the harsh envirobmental conditions of Metema indicates its potential for motton production with similar agro climatic conditions.

  
  

• Crossing of Gumuz sheep with Rutana practiced by the farmers and the declining number of these sheep population needs urgent remedy to save the breed as a genetic resource.

Acknowledgement

The field research was fully financed by the Amhara Regional Agricultural Research Institute (ARARI) in Ethiopia. The authors are grateful to the staff of Gonder Agricultural Research Centre. We are also grateful for the sheep owners for allowing their animals to work upon.

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Received 15 January 2011; Accepted 13 March 2011; Published 1 May 2011

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