A conceptual review on breeding and conservation approaches for Tikur sheep population

Abstract

The objective of the review is to suggest breeding and conservation strategies for the Tikur sheep population. Determination of breeding and conservation strategies for livestock improvement mainly relies on the breed merits of the animals. Tikur sheep are the dominant sheep types in the highlands of the North Wollo Zone. They have unique adaptive merits for a subalpine cool environment. The farmers primarily rely on sheep production in these areas. Adequate information on the production and reproduction performances of Tikur sheep is available in the works of literature. This information could aid future decisions on the management, conservation, and genetic improvement of the sheep. However, breeding and conservation strategies have not yet been documented in the sheep. More than 4500 Awassi crossbred rams have been randomly introduced nearly in all districts of the highlands of North Wollo Zone to improve the wool and meat production of the sheep for four decades and resulting in extensive and indiscriminate mating between Awassi crossbred rams and Tikur sheep ewes. The genetic diversities of Tikur sheep have been now threatened due to indiscriminate cross-breeding, lack of breeding policy, and production advantages. Besides, no effort has been made to conserve and improve the sheep in the research stations; but good attempts have been made to protect and improve the Menz, Horro, Bonga, and Afar in the research stations. Therefore, it is time to call for conservation-based genetic improvement approaches for sheep. In-situ conservation complemented with designing community-based selective breeding is the primary strategy to preserve and improve the sheep.

Keywords:

• Breeding Strategy
• Conservation
• Performance
• Tikur Sheep
• Awassi Breed

PUBLIC INTEREST STATEMENT

Tikur sheep is the dominant sheep breed in the sub-alpine cool highlands of North Wollo Zone, which is characterized by extremely cold weather conditions, serious feed and water shortages, and high disease and parasite exposures. The sheep have excellent adaptive traits. However, these sheep have been indiscriminately crossbred with exotic sheep and their genetic diversities are now declined. The situation calls for conservation-based genetic improvement. The review is aimed to suggest the breeding and conservation strategies of the sheep. It is research-based and crucial for developing and implementing suitable conservation-based genetic improvement strategies. The review can also serve as baseline information for policymakers, researchers and agricultural offices, and students to take necessary actions on the sheep genetic improvement, conservation, and management and undertake further study on the sheep. Moreover, it provides a comprehensive understanding of the performances, unique features, and breeding and conservation strategies of the sheep to the readers.

1. Introduction

Ethiopia is the 2^nd in Africa and six^th in the world in sheep population (Demelash et al. 2006; CSA, 2020). In the country, there were approximately 40 million sheep (CSA, 2020). The Amhara National Regional State has 10.4 million heads of sheep which is about 26% of the national sheep population (CSA, 2020). The country is not only rich in livestock numbers but also rich in genetic diversity that has been developed by natural selection (Galal, 1983). Sheep have served as a ready cash income to meet immediate needs. They are sources of acquiring agricultural inputs, paying school fees, taxes, and medical bills, and purchasing large animals. Sheep are also a reserve against economic and agricultural production hardship or monetary savings and investment in addition to many other socioeconomic and cultural functions (Markos, 2006).

The dominant sheep breed in the highlands of the North Wollo Zone is sub-alpine short fat-tailed (Tikur sheep) (Gizaw et al., Gizaw Solomon et al., 2008; Tassew, 2012). The sheep are widely distributed in the highlands of West Ethiopia (part of Tigray, Gondar, and Wollo) (Gizaw Solomon et al., 2008). They are characterized by predominantly black coat color (60%), fat tail type (100%), cylindrical with turned up at the end tail shape (84.9%), short and semi-pendulous ears, compact body and small body size (Gizaw Solomon et al., 2008; Tassew, 2012). They are also mostly covered with coarse medium hair with a wooly undercoat. Most rams have curved horns with backward orientation while ewes are usually hornless (Gizaw Solomon et al., 2008; Tassew, 2012). The average heart girth, wither height, and body length of the full-mouth female sheep in the breed was 68.13 ± 4.71 cm, 62.98 ± 4.74 cm, and 54.86 ± 5.45 cm, respectively. Male sheep weighed 25.86 ± 0.20 kg whereas female sheep weighed 22.5 ± 1.155 kg (Tassew, 2012). Besides, the sheep do have unique features which can be described as they can: adapt to sub-alpine cool highland weather conditions and living, producing, and reproducing with serious feed and water shortages. The sheep are also disease and parasite resistant and widely used for home consumption during the whole holidays celebrated in North Wollo Zone as compared to Afar sheep found in low lands of the zone. According to the farmers interviewed during a preliminary survey in 2012, their meats are lean and tasty (Tassew, 2012). On the other hand, the Afar sheep breed is fat-tailed and the tail was curved upward having a wider tail both at the base and at the tip. The major coat colour of the sheep varies from white to light red (90%). Both sexes of the Afar sheep breed are polled. The majority of the Afar sheep were shortly eared showing a tendency of inclination downwards (78.6%). Afar ram attains sexual maturity at an average age of 7.1 months. Age at the first lambing and lambing interval of Afar sheep were 405.6 days and 270.5 days, respectively. The body weight of mature Afar ram and ewes were 29.0 ± 0.84 and 24.5 ± 0.14 kg, respectively (Tesfaye, 2008).

Adequate information on the performances of the sheep is available in the works of literature. This information could aid future decisions on the management, conservation, and genetic improvement of the sheep. However, breeding and conservation strategies have not yet been documented in the sheep; even though extensive and unplanned crossbreeding has been implemented in the sheep. No/little effort has been made to conserve and improve the sheep in the research stations by government and non-government organizations; but good attempts have been done to protect and improve the Menz, Horro, Bonga, Afar, and Somalia Black Head sheep in the research centers of Ethiopia (Gutu et al., 2015; Workne et al., 2004). In these regards, the current situations demand urgent conservation-based genetic improvement approaches. Thus, the objective of the review is to suggest the breeding and conservation strategies of Tikur Sheep based on the previous study findings and conceptual interpretations.

1.1. Tikur sheep production in Ethiopia

1.1.1. Sheep genetic resources in Ethiopia

Ethiopia is endowed with a large sheep population with diverse breeds. The country has 40 million sheep (CSA, 2020) (Table 1). The Ethiopian sheep population is almost entirely composed of indigenous animals. About 99.6% and 0.3% of the total sheep population are indigenous breeds and hybrids, respectively (CSA, 2020).

Table 1. Estimated numbers of sheep in Ethiopia by region

Region	Sheep
Tigray	2,097,619
Afar	4,040,176
Amhara	10,386,223
Oromia	9,260,493
Somale	9,188,394
Benshangul-Gumuz	72,284
SNNP	4,735,604
Gambela region	43,903
Harari	4,236
Dire Dawa Astedader	65,462
Total	39,894,394

Source: CSA (2020).

The country is not only rich in livestock number but also rich in genetic diversity that has been developed by natural selection (Galal, 1983). Diversity is a potential opportunity to obtain promising sheep which can meet the current and future production demands. Sheep development should base on local sheep genetic resources. If we are not properly handling it, we will lose it and face difficulties to restore again. The indigenous sheep evolved in varied agro-ecologies with varied climate conditions. The Tikur sheep well adapt the sub-alpine cool agro-ecologies similar to the Menz sheep compared to the Afar sheep which well adapt to arid environments (Gizaw Solomon et al., 2008; Gutu et al., 2015; Tassew, 2012). These two environments are characterized by extreme cold weather and serious shortage of feed shortage. Exotic sheep cannot perform well in these environments. This meant that getting animals that survive, reproduce and produce in this extreme cold environment if we lost our indigenous sheep resources could be difficult.

1.2. Merits of Tikur sheep

Tikur sheep have unique features/merits/that are acquired by natural and human selection over generations. The average breed merits which had been calculated as average economic, ecological, and socio-cultural merits were 0.33% (Gizaw Solomon et al., 2008). To this end, it was ranked 4^th among the 14 sheep breed in Ethiopia (Gizaw Solomon et al., 2008). They are the dominant sheep types in the highlands of the North Wollo Zone (Figure 1). According to the farmers interviewed during a preliminary survey in 2012, their meats are lean and tasty (Tassew, 2012). The sheep have also satisfactory growth and reproduction performances as compared as the indigenous sheep types in Ethiopia (Tassew, 2012; Tassew Mohammed & Alemayehu, 2017).

Figure 1. Ewe and ewe lambs (left) and rams (right) of Tikur sheep.

According to the key informant interviews during focus group discussions in 2012 and 2017, it is the production environment, not the genotype that makes our indigenous animals poor in production and reproduction (Tassew, 2012; Tassew Mohammed & Alemayehu, 2017). Our indigenous animals have evolved with serious feed and water shortages, extreme weather conditions, and higher disease exposure from early gestation to throughout their lives. Serious feed shortage results in a permanent effect on subsequent survival, growth, and health. This permanent effect is hereditable. Indigenous animals are subjected to these stresses for many generations. Moreover, the majority of the animal performances (75%) are determined due to the production environment whilst the genotype contribution for animal performances is small (25%) (Bourdon, 2000). Therefore, as far as, we have a large sheep population and apply the best husbandry management, we can get promising sheep from our indigenous sheep type.

1.2.1. Performances of Tikur sheep

The characteristics of Tikur sheep were studied by various authors (Gizaw Solomon et al., 2008; Tassew, 2012; Tassew Mohammed & Alemayehu, 2017). The results of previous studies clearly indicate that the performances of Tikur sheep were found to be satisfactory for major productive and reproductive traits (Tassew Mohammed & Alemayehu, 2017). Their reproductive performance values had fallen under the Ethiopian sheep reproductive performance ranges. The age at first mating, age at first lambing, lambing interval, and annual reproductive rate were 8.14 ± 0.14, 13.94 ± 0.86, 8.92 ± 1.10 months, and 1.44 ± 0.26, respectively (Tassew Mohammed & Alemayehu, 2017). The age at first mating and lambing was not therefore delayed. Similarly, the length of the lambing interval was not long. However, they delivered single lamb per lambing even though there were considerable numbers of ewes that lambed twins per lambing and the number of lambs per ewe per year was good. The average litter size of Tikur sheep (1.04) was in agreement with the litter size values reported for Black Head Somalia (1.04) by Galal (1983) and Menz sheep (1.03) by Markos (2006). Litter size might be improved by 10–40% through premating ewe nutrition management or treatment with gonadotropins (Mukasa-Mugerwa & Lahlou-Kassi, 1995).

For their growth performances, they are not also far from the average growth performances of Ethiopia sheep for almost all parameters considered in the monitoring study. Even they performed better than other sub-alpine sheep in the Amhara region for certain growth traits. The birth, weaning, six-month, nine-month, and yearling weights of the sheep were 2.47 ± 0.47, 11.89 ± 2.26, 15.76 ± 1.49, and 16.49 ± 1.25 and 21.33 ± 3.27 kg, respectively (Tassew Mohammed & Alemayehu, 2017). These clearly show that body weight at market age is satisfactory. The 270 days body weight and yearling weight are also good. The birth weight which has a high contribution to good subsequent growth and lamb survival is also appreciable. Generally, Tikur sheep have attractive growth potential which is important for meat production. Besides, the linear body measurement performances of the sheep were found to be comparable. The average heart girth, wither height, and body length of the full-mouth sheep in the breed was 68.13 ± 4.71 cm, 62.98 ± 4.74 cm, and 54.86 ± 5.45 cm, respectively. Mature male sheep weighed 25.86 ± 0.20 kg whereas female sheep weighed 22.5 ± 1.155 kg (Tassew, 2012).

1.3. Genetic improvement of Tikur sheep

Determination of breeding strategy for livestock improvement mainly relies on the breed merits of the animals. To this end, reviewing and documenting the growth and reproductive performances of the sheep are important. Tikur sheep are the dominant sheep types in the highlands of the North Wollo Zone. The highland parts of the North Wollo zone (Figure 2) are described with extremely cold weather conditions, serious feed, and water shortages, and high disease and parasite exposures (MoA, 1998). The farmers primarily rely on sheep production in these areas; however, these environments do not favor the exotic sheep and their crosses (Gizaw et al., 2013; Gutu et al., 2015).

Figure 2. Map of North Wollo Zone where Tikur sheep are dominantly found.

In Ethiopia, crossbreeding attempts have been made to improve the productivity of indigenous sheep through crossing with exotic breeds such as Corriedale, Hampshire, Romney, Awassi, and Dorper (IBC, 2004; Solomon & Getachew, 2009). However, these programs have not been successful, probably because of a lack of understanding of the preferred breeding objectives of the farmers and the absence of involvement of all stakeholders in the designing of breeding strategies (Gemeda Duguma et al., 2010; Markos et al., 2006). Moreover, on-farm studies indicate that crossbreds are not superior to purebreds under low-input conditions (Hassen et al., 2002). The on-farm monitoring study conducted by Tassew Mohammed and Alemayehu (2017) to evaluate the performances of Tikur sheep has indicated that the sheep have good and comparable productive and reproductive performances. Community-based breeding applied to Menz sheep raised in similar agroecology to Tikur sheep was also successful. A community-based breeding research project carried out on the Menz sheep in the Menz district of Amhara National Regional State (ANRS) reported a 3% improvement in the 6-month body weight in the 2^nd generation of lambs over the base population (Slomon et al., 2013). There are also community-based sheep and goat breeding program in the Amhara region which has been implemented by the International Center for Agricultural Research in the Dry Areas (ICARDA), the International Livestock Research Institute (ILRI), and the University of Natural Resources and Life Sciences (BOKU) in the collaboration with Ethiopian National Agricultural Research System. The community-based breeding program was initiated and operated in 2009. These experiences enhance to the analysis of the success and failure stories of the programs and take lots of lessons that are relevant for better designing and implementing genetic improvement of Tikur sheep. The community-based breeding program is advocated for low-input traditional smallholder farming systems (Haile et al., 2009; Kahi et al., 2005; Wurzinger et al., 2011). This is because the community-based breeding program takes into consideration the indigenous knowledge of the communities on breeding practices and breeding objectives. The community-based breeding strategies also account for the production system holistically and involve the local community at every stage starting from planning up to the end of the breeding program operation (Baker & Gray, 2004; Gizaw et al., 2013). Sustainable animal breeding strategies require a broad definition of breeding objectives that emphasize maintaining adaptation and biodiversity in addition to profitability. Thus, community-based breeding which is a kind of selective pure breeding of the adapted indigenous breeds is the best possible option for the genetic improvement of the sheep. However systematic/controlled crossbreeding with imported genotypes may also be considered as a second option for areas with good feed supply and a high level of management to improve the performances of the sheep. The breeding strategy for the sheep is decided based on the analysis of previous research results and conceptual interpretations.

North Wollo is one of the ten zones of the Amhara Region in Northern West Ethiopia. It is located at 11° 49’ 59.99“N latitude and 39° 14’ 60.00” E longitude in the North West of Ethiopia (Svein & Adal, 2002). The altitude ranges from 700 to 4,260 meters above sea level (m.a.s.l) and the annual rainfall varies from 880 millimeter (mm) to 1,772 mm with a maximum temperature of 44.5 degree Celsius (^oC) in the lowland and minimum temperature of −10 °C in the highland (Svein & Adal, 2002). Sand and clay soil are the two dominant soil types in the areas. The zone is generally divided into three main agro-climatic zones, namely: highland (>2500 m.a.s.l), mid-highland (1500–2500 m.a.s.l), and lowland regions (<1500 m.a.s.l) (Svein & Adal, 2002). It receives a bimodal rainfall (SARC, 2010), namely the main rainy season and the short rainy season. The main rainy season extends from the end of June to mid of September while the short rainy season starts at the end of January and lasts up to the end of April.

1.3.1. Conservation approaches

Conservation is defined as the improvement and utilization of livestock genetic resources without interfering with their long-term use. Either In-situ or Ex-situ conservation can be applied to prevent the animals from loss of genetic diversity or breed extinction. In-situ is maintaining live animals in their original environments whereas Ex-situ maintaining animals out of home areas in the form of live animals or germplasms (ova, semen, and embryo) with cryopreservation techniques. No previous attempt has been performed to conserve and improve the sheep in the research stations. However good works/attempts/have been done to protect and improve the Menz, Horro, Bonga, and Somalia Black Head sheep in the research centers of Ethiopia (Gutu et al., 2015; Workne et al., 2004). Conservation-based selective breeding programs resulted in appreciable and encouraging genetic progresses in meat and wool production. In the Menz sheep population, body weights at birth, 3 and 6 months of age increased by 0.42, 2.29, and 2.46 kg, respectively, in the third generation over those in the base generation (Gutu et al., 2015; Slomon et al., 2013). In the same sheep population, ewes conceive on regular basis and give birth usually two times a year. The newborn lambs are attractive and grow fast. Body conformation, appearance, and other preferred traits of lambs are found to be superior (Gutu et al., 2015; Slomon et al., 2013). Similarly, a good genetic gain of 0.4 kg was obtained per year in the Bonga sheep population. Encouraging improvements were also observed in the body size of newborn lambs, lambing interval, twinning rate, and change in coat colour towards uniform and preferred colour of the sheep (Gutu et al., 2015; Slomon et al., 2013). These experiences enhance to take lots of lessons that are relevant for better designing and operating conservation-based genetic improvement programs in the Tikur sheep. We are concerned about the conservation of Tikur sheep because of the fact that the sheep possessed unique merits, high within-breed variations in performance traits, and satisfactory production potential. In spite of total breed merits, the extinction probability, which was calculated based on indicators of threat status, was more than 30% (Gizaw Solomon et al., 2008). More than 4500 Awassi crossbred rams have been introduced nearly in all districts of the highlands of North Wollo Zone from Debre Birhan Research Centers by Amhara Region Agricultural and Rural Development Beauro to improve the wool and meat production of Tikur sheep for four decades. However, the introduction of the crossbred rams has not been planned and controlled (Gizaw and Tassew Mohammed & Alemayehu, 2017; Tesfaye, 2008). The strategy for dissemination of genetic improvement to villages and sustaining crossbreeding at the village level is not also well defined. Extensive and indiscriminate distribution of the crossbred rams across the country for the last four decades yielded virtually no impact on the sheep industry. It results in extensive and indiscriminate mating between Awassi crossbred rams and Tikur sheep ewes. Farmers have been also trained and advised to keep the exotic crosses (Tassew Mohammed & Alemayehu, 2017). Their breed preferences trend has indicated a shift from indigenous to Awassi crossbreds due to the reason that high production (wool and meat) advantage has been obtained from the crossbreds than the indigenous. Moreover, the lack of a breeding policy to maintain and improve the sheep may also be the contributing factor to the uncontrolled crossbreeding of the sheep with exotic crossbred rams. These and other factors resulted in the loss of genetic diversities of the indigenous Tikur sheep population and the breed or population has been now seriously affected (Gizaw and Management Entity, 2021; Tassew Mohammed & Alemayehu, 2017; Tesfaye, 2008). The genetic diversities of the indigenous Tikur sheep population have declined in the past four decades (Gizaw and Tassew Mohammed & Alemayehu, 2017; Tesfaye, 2008).

In the other scenarios, it may not be effective to run sustainable sheep production with Awassi crossbreds at the smallholder farmer level. The reasons are: there have also been problems in the production of crossbred rams, the pure Awassi breeds are now challenged with the viral disease (Maedi-Visna) (Gizaw et al., 2013) in the multiplication center, crossbreeding is considered a threat to the survival of the adapted indigenous breeds and crossbreeding as a strategy failed to sustain genetic improvement in village flocks owing to exotic genotypes being maladapted to the local environment (Slomon et al., 2013).

Thus if these sheep are missed due to misuse and negligence, getting a breed that can adapt and reproduce in the resource-poor cool highlands of North Wollo Zone is difficult. The farmers will suffer more if unforeseen conditions happen to this end. Therefore the farmers, research centers, universities, Ethiopian Biodiversity Organization, Regional and Federal Governments, and Non-Government organizations need to be concerned to conserve and improve the sheep.

For Tikur sheep conservation, both In-situ and Ex-Situ conservation strategies can be considered but the emphasis should be given to In-situ conservation at farmer levels through designing community-based selective breeding by Agriculture Extension Offices, Research Centers, Non-Government Organizations, Livestock Agencies, and Universities. The conservation strategy is also suggested based on the analysis of previous research results and conceptual analysis. The government and other bodies should also plan important activities to encourage the farmers to keep and improve the sheep.

2. Conclusion

Tikur sheep have unique adaptive merits for sub-alpine cool environments. The results of previous studies clearly indicate that the performances of Tikur sheep are found to be satisfactory for major productive and reproductive traits. The genetic diversities of the sheep have been threatened due to extensive and indiscriminate crossbreeding with Awassi sheep. Community-based selective breeding complemented with good husbandry management has to be the priority breeding strategy whereas delineated crossbreeding with imported genotypes may also be seen as a second option for areas with a good level of management to improve the performances of the breed whereas In-situ conservation under farmer levels should be the primary conservation strategy to protect the sheep. The government and other bodies should plan important activities to encourage the farmers to keep and improve the indigenous Tikur sheep. Further research should be conducted on developing and implementing of suitable conservation-based genetic improvement strategy in Tikur sheep population.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Notes on contributors

Tassew Mohammed

Tassew Mohammed Ali (Ph.D.). I got my MSc and Ph.D. degrees in Animal Genetics and Breeding from Haramaya University, Ethiopia, and Guru Angad Dev Veterinary and Animal Sciences University, India, respectively. I have been working in the Department of Animal Science, at Woldia University as Assistant Professor. I have also served as Research and Community Service Coordinator, and Vice-dean of the College of Agriculture. I am well experienced with SAS and R statistical software packages. I successfully completed several research activities on sheep and found satisfactory results on the production, reproduction, and adaptive performances of Tikur sheep. Tikur sheep particularly have unique adaptive characteristics. The results of the research serve as baseline information for policymakers, researchers, and agricultural offices to take necessary actions on the sheep genetic improvement, conservation, and management and undertake further study on the sheep. I published more than seven research articles in international journals.