| Livestock Research for Rural Development 24 (7) 2012 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
Well-designed cattle crossbreeding programs may lead to exploit heterosis for traits of economic relevance. Exotic dairy cattle breeds were introduced six decades back to upgrade indigenous zebu in Ethiopia. Various efforts have been made to improve dairy sector through artificial insemination (AI), shared crossbred bull service or by distributing crossbred F1 heifers particularly to the smallholder dairy farmers in urban and peri-urban areas.AI service in the country was not successful to improve reproductive and productive performance of dairy industry.
The problem is more aggravated by wrong selection and management of AI bulls along with poor motivations and skills of inseminators. Unorganized crossbreeding program, absence of crossbreeding policies and lack of records to evaluate the performance from lower farmer level are some constraints and these would put a threat to farm animal genetic resources (FAnGR) of Ethiopia in the future. Therefore, the dairy cattle genetic improvement programs need to be subjected to national evaluations and redesign appropriate strategies that would be more responsive to the currently changing scenarios in the country
Key words: Crossbreeding, exotic genes, Zebu
Historically, domestication and the use of conventional livestock breeding techniques have been largely responsible for the increases in yield of livestock products that have been observed over recent decades (Leakey 2009). Because, the productive and reproductive potentials of Zebu cattle are relatively low, crossbreeding with B. taurus (which combines additive, dominance and epistatic effects of the two genotypes), ensures high productive and reproductive performance. It also appears important to estimate the expected level of heterosis for traits of economic interest in dairy cattle in order to evaluate the profitability of crossbreeding (Mauro et al 2009).
In Africa, crossbreeding has resulted in good improvements in production of milk and meat, especially when supplemented with adequate management levels in terms of nutrition and disease control. In spite of, the presence of large and diverse animal genetic resources, the productivity of livestock remains low in many developing countries including Ethiopia for various reasons such as inadequate nutrition, poor genetic potential, inadequate animal health services, and other management related problems (Fikre 2007). The effect of crossbreeding has also been disastrous, especially in the smallholder sector where less attention is paid to matching the genotype to the environment (Kahi 2002).According to Fedlu et al (2007), Ethiopian cattle genetic diversity is currently under threat mainly due to unplanned as well as indiscriminate crossbreeding, and to some extent interbreeding among the local populations.
Artificial Insemination (AI) practicing as cattle genetic improvement program accounted about six decades in Ethiopia but, coming with little success. The most important constraints associated with were loss of structural linkage between AI Center and service giving units, absence of collaboration and regular communication between National Artificial Insemination Center (NAIC) and stakeholders, lack of breeding policy and herd recording system, inadequate resource in terms of inputs and facilities, and absence of incentives and rewards to motivate AI technicians (Desalegn 2008).
However, there is little quantified information as to the impact of livestock interventions on the diversity of indigenous farm AnGR (Animal Genetic Resource) of Ethiopia. The extent to which the exotic genotypes have diffused into the indigenous populations and the level of dilution is not objectively assessed. But, available estimates indicated that crossbred cattle make only 1% of the total cattle population of Ethiopia (Workneh et al 2002).This indicates that the trend is very slow. The objective of this review was to quantify status of cattle genetic improvement in Ethiopia with following specific objectives
To assess the trends of cattle crossbreeding and its effect on genetic diversity
To quantify the effectiveness of cattle genetic improvement programs in Ethiopia from its base
To identify the challenges and opportunities facing improvement interventions of the programs
Cattle genetic improvement program in Ethiopia has been started with dairy cattle improvement to enhance milk production of local breeds. The program was launched during the occupation of Ethiopia by Italy with importation of exotic dairy cattle breeds. Later on, the first livestock development project (1958-1963) created the Dairy Development Agency (DDA) that was concerned mainly with the development of commercial dairy farms in Addis Ababa (Fekadu 1990).Following this Chilalo Agricultural Development Project (CADU), an integrated project established jointly by the Ethiopian and Swedish Governments, in Arsi region initiated intensive small scale dairy development in Ethiopia in 1967/68 (Kiwuwa et al 1983). This was followed by the Wolaita Agricultural Development Project (WADU) that was established in 1971 and funded by the World Bank, applied the CADU program (Haile Mariam 1994). Production of deep-frozen semen started at CADU in 1973. CADU in Assela, and WADU in Welaita, continued breeding and distributing crossbred dairy cows to farmers using the artificial insemination services available. In 1987, a FINNIDA funded project of the MOA started to improve dairy cattle productivity at the highlands of Ethiopia through the establishment of the Selale Peasant Dairy Development Pilot Project (SPDDPP). SPDDPP introduced crossbred dairy cattle and improved management skills with the objective to increase the living standard of smallholder farmers (Kelay, 2002). The focus of the program was on increasing the milk productivity of local breeds through crossbreeding and distribution of F1 heifers to farmers (Ethiopian Agricultural Research Organization 1 2001).
Since 1995, the Smallholder Dairy Development Project, SDDP, that were considered as the continuation of the pilot project with the same objectives but broader spectrum of activities operated in the different parts of the country. The project had been distributing crossbred dairy cows and purebred Friesian and Jersey breeding bulls and introduced improved methods of fodder production in the project areas (MOA/SDDP 1996) . According to the 1999 SDDP report of the Oromia Regional Government, the project had distributed 167 in calf heifers and 58 breeding bulls to contact farmers at Selale area. Despite of all these trials, the numbers of crossbred cattle make only 1% of the total cattle population of Ethiopia (Workneh et al 2002).
Then national artificial insemination centre was established in 1981, with the mandate to serve at the country level. It is a government organization that makes this service available to rural, peri-urban, and urban areas through the regional offices throughout the country. The main objective of the support was to achieve an efficient and reliable artificial insemination service. Initially, service was based on production and use of fresh semen until the liquid nitrogen plant was installed in 1984. Bulls donated by the Cuban Government (25 Holstein and 10 Brahman) and importation of 44,800 doses of Friesian and 2,000 doses of Jersey semen were the source of semen used for frozen semen technology . To date, semen collection was based on exotic and indigenous, as well as crosses of these breeds, namely Friesian, Jersey, Brahman, Boran, Barka, Fogera, Horo, Sheko, and crosses of 50% and 75% Holstein-Friesian indigenous bulls. From the total semen produced, the major share is from Friesian (75.3%), followed by Jersey (10.5%). The NAIC at Kality, is serving as the main semen collection and preservation center; the satellite AI centers to be used for services, and thenHoletta bull/dam farm, was the base for nucleus bull-producing, testing and rearing farm (Getachew and Gashaw 2001). Later production of semen from crossbred animals (Friesian x Fogera, Friesian x Boran, Friesian x Barca, Friesian x Arsi) and from indigenous breeds (Barca, Borana and Fogera) are undertaken and some doses were distributed. From 1981 till 1999 a total of more than 300,000 semen doses were produced and distributed by NAIC (1999).
So, crossbreeding has been started by the Institute of Agricultural Research, through the establishment of an on-station Dairy Cattle Crossbreeding Program, using Friesian, Jersey and Simmental sires that were crossed with the local Horro, Boran and Barka dams with the aim of testing the productivity of crossbred dairy cows with different levels of exotic blood (EARO 1 2001). During the 1970’s, governmental and non-governmental organizations have made various efforts to improve the dairy sector by establishing dairy cattle improvement ranches and distributing crossbred F1 heifers to smallholder farmers (EARO 2001; Kelay 2002).
Until the establishment of National Artificial Insemination Centre (NAIC) in 1981, organizations like, DDA (Dairy Development Authority) and CADU (Chilalo Agricultural Development Unit) /ARDU (Arsi Rural Development Unit) performed a total of 3924, 5800 and 64,887 inseminations, respectively by importing semen and liquid nitrogen. Later on bull stations and semen laboratory were constructed in Assella. From 1984-2000 a total of 351,037 inseminations and 120,684 births of graded calves were recorded after the establishment of NAIC.
Although crossbreeding in form of AI has been in operation in Ethiopia for over 30 years, the efficiency and impact of the operation has not been well documented. As cited in Alemayehu (2010) it is widely believed that the AI service in Ethiopia has not been successful (Sinishaw 2004). It is weak and even declining due to inconsistent service in the smallholder livestock production systems (Ababu et al 2006). Cattle breeding are mostly uncontrolled in Ethiopia making genetic improvement difficult and an appropriate bull selection criteria have not yet been established, applied and controlled (Azage et al 1995). AI coverage is from <2% in Africa to just over 12% in Asia and near east. In Ethiopia, information about AI coverage is not available, but it would be <1% even if all exotic and crosses are inseminated. This suggests that the total number of both exotic and hybrid female cattle produced through the cross breeding program during the past several decades is quite insignificant. About 93% of users are dissatisfied (Desalegn 2008).
Crossbred animals may lead to an advantage if economically important traits show heterosis, but the mere evidence of non-additive genetic effects is not enough to state that crossbreds are better than purebred individuals are. Since genotypes do not perform equally under different production environments, including different economic and managerial conditions, it appears important to consider the environment in which genotypes are producing. Falconer (1952) nicely explained this situation, known as genotype by environment interaction. This is a crucial point that has to be borne in mind when deciding the mating strategies to be adopted to maximize the farm profit: the comparison cannot be at the individual animal level but at the system level.
However, at farm level, the genotype of crossbred animals kept by producers is likely to include any percentage of foreign genetic material due to unsystematic breeding practices, unplanned mating schemes, uncontrolled AI services and bull distribution. There is no controlled breeding in communal grazing areas where exotic bulls are introduced and allowed to indiscriminately mate with local cows. Such schemes have resulted in a complex mixture of genotypes and possibly threats to indigenous AnGR gene pool. In the absence of a clearly defined breeding policy, crossbreeding is bound to cause genetic erosion resulting in loss of adaptation and loss of probably unique genetic identities of indigenous animal genetic resource (IBC 2004).
Moreover, mating of different genotypes increases health and efficiency in animals, and the improvement of reproductive and fitness traits such as fertility, survival, and calving ease, seems to be an important aspect for implementing crossbreeding in dairy cows (Heins et al 2006a, b), together with an achievable economic advantage in milk pricing systems where fat and protein are rewarded (Weigel and Barlass 2003).The genetic superiority of Holstein-Friesian cows compared with crossbred animals and other breeds has encouraged its adoption in most countries where dairy cattle breeding has covered an important role on livestock production and where milk volume has been of great importance in determining income for the dairy farm (López -Villalobos 1998).
According to Kefena et al (2011) comparison of milk production and reproduction performances, Frisian crossbred dairy cows were more productive than Jersey crosses in central highlands of Ethiopia. However, Jersey crossbred dairy cows have shorter lactation lengths and calving interval than Frisian crossbred dairy cows that reflects better reproduction efficiencies in Jersey crosses. However, continuous decline in the milk production traits over time accompanied by substantial improvements in reproduction traits showed gradual deterioration in the genetic components of the breeding programs. It generally reflects the lack of efficient selection program, absence of periodic monitoring of the genetic progresses attained and use of sires with low breeding value. Therefore, the dairy cattle genetic improvement programs of Ethiopia need to be subjected to national evaluations to redesign appropriate strategies that would be more responsive to the currently changing scenarios in the country.
Crossbreeding has been widely used in order to combine the high milk yield potential of exotic breeds with the adaptability of the local ones. Crossbreeding of Bos taurus dairy breeds with local Bos indicus cattle is a well-documented strategy to enhance milk production in the tropics (Cunningham and Syrstad 1987). The first crossbred generation (F1), usually from native females mated with exotic males, has been a success in most cases. The F1 crosses can produce up to three times more milk, and have longer lactation and shorter calving intervals than the local breeds (Million and Tadelle2003). However, backcrossing to the European breeds gave rather disappointing results; i.e. milk yield increased only slightly or even declined, and fertility deteriorated. This is in addition to the lack of adaptation to tropical conditions (Syrstad 1989).
Increased genetic diversity in African cattle is believed to be a result of high levels of genetic introgression of B. indicus and B. taurus (Freeman et al 2004). According to Zarabruket al (2011), North Ethiopian cattle are highly introgressed by the Zebu cattle from Indian zebu, and African, European and the Near-Eastern taurine ancestry. The same authors also stated that there is high level of genetic diversity within and low level of population differentiation among North Ethiopian cattle breeds (Afar and Raya from Sanga type; Abergelle, Arado, Irob and Fogera from Zenga type and Begait from Large East African Zebu) is probably due to multiple crossbreeding events in East Africa.
The average epistatic loss due to the breakdown of all types of gene interactions involving two or more loci, as a deviation from the average additive and dominance effects which is estimated by direct epistatic and maternal epistatic effects (Fries et al 2002). Epistasis plays an important role in the performance of Bos indicus × Bos taurus crossbred calves. The inclusion of profit heterosis or complementarities on crossbred genetic evaluation models seems to be important (Carvalheiro et al 2006).For instance, the decreases in milk yield of high grade (above 3/4 Holstein Friesian) compared with the F1 crosses might be related to the breakdown of genes due to epistatic effect; however, since the number of animals available for this group were small, the results needs to be interpreted with caution (Million and Tadele 2003)
The existence of genetic polymorphism or diversity in a population is the basis of genetic improvement by selection and needs to be accurately estimated (Tautz 1993). Designing of a breeding program also needs to take into consideration a mechanism that ensures conservation of animal genetic resources (Aynalem et al 2011). However, crossbreeding was and still is perceived as “the way forward” to improve productivity of indigenous livestock under smallholder conditions and development policies has largely ignored adapted farm animal genetic resources (ILRI 1999). Crossbreeding with exotic breeds clearly is a major factor contributing to the erosion of locally adapted AnGR (Köhler-Rollefson 2004).Crossbreeding also results inconsistent and rapid loss of genetic diversity by dilution of the autochthonous genetic makeup.
Major causes threatening diversity of genetic resources in Ethiopia include poorly designed and managed introduction of exotic genetic materials, droughts and consequences of drought associated indiscriminate restocking schemes, political instability and associated civil unrest, and weak development interventions (Nigatu et al 2004). The effects of the misguided and uncontrolled introduction of exotic genes and that of interbreeding among indigenous breeds might require application of molecular genetics for purposes of precision. In extreme scenarios, however, it could have a drastic effect leading to extinction of a breed within few generations (ESAP 2004).
Even indigenous genotypes may well be adequate and able to respond sufficiently to reasonable economic improvements in their production system (Workneh et al 2003), trends already exist in Africa and the population of pure indigenous cattle breeds is likely to diminish because of crossbreeding or neglect of local animal genetic resource (Rege 1992). As a result, some of the animal genetic resources of Africa are endangered and, unless urgent concerted efforts are made to characterize and conserve, these may be lost even before they are described and documented (Zewdu et al 2008).Loss of genetic diversity increases the risk of difficulties in subsistence for the millions of livestock keepers who depend on these resources to secure their livelihoods (Fedlu et al 2007).
The application of AI in indigenous cattle using semen from exotic cattle breeds is, for instance, resulting in unforeseen substitution of indigenous genes by exotic genes (ESAP 2004; IBC 2004). The application of these technologies for germplasm propagation and dissemination may contribute to the erosion of diversity. Unique germplasm is threatened by replacement of breeds with more productive or popular stocks, dilution of breeds through crossbreeding programs, and decreased diversity within highly selected breeds or lines that have a small number of breeding individuals (FAO/IAEA 2009).
In situ conservation schemes involve support of live populations of such size that viable breeding programs should be possible to maintain, while avoiding inbreeding problems. The aim of ex situ conservation schemes is twofold: maintaining gene banks by cryopreservation (semen and embryos) and, if possible, maintaining the remaining small populations (FAO 2007a; FAO 2011). But currently those techniques were not as such effective and sustainable to safeguard genetic diversity of local genotype at farmer level.
Recent research on genetic evaluation of reproduction traits with 15-year data for Ethiopian Boran and Holstein Frisian crosses from Debrezeit and Holleta agricultural research station revealed that improved herd reproductive management practice and within-breed selection could substantially improve the reproductive performance of the indigenous Ethiopian breeds. Use of crossbreds is also advised under suitable production system. However, as the level of management achievable under most smallholder conditions in Ethiopia is rather unfavourable to higher exotic inheritance levels than 50% Holstein Friesian inheritance (Aynalem et al 2009).
Given suitable government recognition, access to market and services, there is great potential for development of smallholder dairy scheme in peri-urban and urban areas (Staal and Shapiro 1996). However, it could still be argued whether the gains attained were commendable when compared to the substantial investment involved in the genotype improvement undertakings, and recent hypothesis suggested that the economic benefits of crossbreeding may have been overestimated as non-market effects and environmental values have not been included in breed comparison studies (Workneh et al 2002). The development of market infrastructure and market institution is also very important for inducing efficiency and incentives for market participants on the value chain. The marketing system should operate efficiently to ensure that the consumer gets what it wants and the producer gets the reforms needed to continue production (Azage et al 2010).
Crossbreeding has principally been applied in the tropics aimed to exploit breed complementarities. Specifically, specialized exotic breeds have been crossed with indigenous breeds to combine the high productivity of the former with adaptive attributes of the latter (Kahi 2002). Exotic animals used in crossbreeding are not naturally adapted to local conditions, so large scale (beyond optimal exotic blood level) crossbreeding should be carried out with caution (FAO/IAEA 2009). In Ethiopia, for traditional highland mixed farming and the smallholder dairy farming systems, introduction of exotic genes at 50% level could be considered best (Aynalem 2006). The same author also suggested, it is possible to upgrade to 62.5% with improving management aspect. Draft policy of Ethiopia livestock development master plan also recommends crossbred cattle whose exotic blood level ranging 50-62.5% is recommended in avoiding the adaptation problems (EARO 2 2001).However, the current the crossbreeding work in Ethiopia, unfortunately, was not based on a clearly defined breeding policy with regard to the level of exotic inheritance and the breed type to be used.
It has been generally accepted that the first-generation cross is well adapted to the environment, performs satisfactorily, and is accepted by farmers. In some farms where the management levels and feeding systems are high enough and acceptable, the levels of exotic blood in dairy cows are as high as 87.50 to 93.75%. Records analyzed from over 21 years (1981-2002)of work on three large dairy farms, namely, Holleta, Stella, and Selale, milk yield of crossbred cows indicate that crosses beyond F1 were showing decreasing trends (Mohammed 2003).He concluded that it was no sustained improvement in the phenotype had been achieved in the 21 years of the study period. In generally; in Ethiopia crossbreeding is non-systematic and uncoordinated, and with the present increasing trend for introduction of high-output animals, unorganized crossbreeding program and absence of crossbreeding policies would put a threat to FAnGR of Ethiopia in the future (ESAP 2009).
AI technology has also lead to one of the most successful smallholder dairy systems in the developing world (Stall et al 2008a). However, the use of AI has also failed in many situations in developing countries because of the lack of infrastructure and the costs involved, such as for transportation and liquid nitrogen for storage of semen or because the breeding programme has not been designed to be sustainable (Mpofu and Rege 2002,Philipsson et al 2005,Azage et al 1995). Improper use of AI for crossbreeding indigenous cattle with exotics may be disastrous when, for example, a long-term strategy lacks information on how to maintain the appropriate level of exotic genes in an environment that cannot support pure exotic breeds. The pros and cons of using AI should therefore be critically reviewed for each case before designing breeding programmes. However, with the sudden change of policy and removal of public support, the AI system simply collapsed.
A recent study by Dessalegn et al (2009) revealed that 82% of the technical staff at NAIC and all participants of focus group discussions confirmed that there are no appropriate collaborations and communications between the NAIC, regional bureaus of agriculture and rural development and other stakeholders. In addition, about 73.3% of the AI technicians do not provide AI service during weekends. With regard to effectiveness of AI service, the overall average conception rate to first service was as low as 16.1%, with significant variations between regions: 21.8% in Addis Ababa; 19.2% in Oromia; 17.7% in SNNPR; 16.3% in Amhara and only 3.7% in Tigray. Although artificial insemination, the most commonly used and valuable biotechnology, (Webb 2003), has been in operation in Ethiopia for over 30 years, the efficiency and impact of the operation has not been well-documented (Himanen and Azage 1998). Reproductive problems related to crossbreed dairy cows under farmers’ conditions are vast (Bekele 2005).
Well-designed crossbreeding programs may lead to exploit desirable characteristics of the breeds or strains involved, and to take advantage of heterosis for traits of economic relevance (López-Villalobos 1998). The issue, however, is how to design sustainable breeding schemes for indigenous breeds under inherent tropical conditions (Rege et al 2011) where resources are limited, feed availability and quality varies greatly depending on the type, geographical location and season, and the demand on animals that are better able to adapt to the ever-changing environment due climate change is increasing.
Identification of breeding goal is the first step in designing genetic improvement strategies. Payne and Hodges (1997) stated that breeding goals should match the expectations and values of the community. Furthermore, each trait in the breeding goal is given a 'goal value', indicating the contribution of the improvement of the trait to the realization of the development objectives. Since the relative rate of improvement will be faster for traits which have higher heritabilities, emphases should be given to traits with acceptable heritability. As a general guideline, traits with heritabilities less than 10% are considered lowly heritable and one cannot realistically expect to make much genetic progress (Funk 1992).
Designing of a breeding program also needs to take into consideration a mechanism that ensures conservation of animal genetic resources (Aynalem et al 2011). Crossbreeding was and still is perceived as “the way forward” to improve productivity of indigenous livestock under smallholder conditions and development policies has largely ignored adapted farm animal genetic resources (ILRI 1999).
Dairy cattle genetic improvement program started in Ethiopia in the early 1970s has never been subjected to periodic evaluation for the genetic and environmental trends. Thus, the effectiveness of this program is not clearly known. Moreover, no information is available on the status of the national dairy cattle genetic improvement program that guide policy makers, development planners and breeders to redesign appropriate breeding programs that respond to the current scenarios in Ethiopia (Kefena et al 2011).
The absence of coordinated systems for data collection and record keeping and the maintenance of databases for the livestock sector, including a mechanism for feedback and exchange among the stakeholders for development of livestock-related policies have been identified as a major constraint. Such data recording, even on a limited scale, is critical for genetic improvement. Success in genetic improvement to a larger extent depends, among others, on accurate recording of the farm operations and periodic analysis of the data to design future plans and take corrective measures as appropriate (Aynalem et al 2011). Lack of record keeping and reporting by AI service providers and farmers has adversely affected national data analysis and decision making on progress and it is also highly believed to have increased the incidence of inbreeding in the country (Desalegn 2011).
Lack of appropriate livestock policies have been identified as one of the increasing key factors causing threats to Farm Animals Genetic Resource (FAnGR) in the developing world (Gibson et al 2006).At present, there is no legal framework in Ethiopia to regulate crossbreeding or to regulate the importation and distribution of exotic genetic materials (ESAP 2007). In an increasingly globalized market, the absence of breeding policies and regulations, as well as the absence of gene bank for animal genetic resource conservation, could put indigenous breeds at risk and endanger the future generations of livestock in Ethiopia and the rest of the world (Desalegn 2008).With the present increasing trend for high-out animals, unorganized crossbreeding program and absence of crossbreeding policies would put a threat to FAnGR of Ethiopia in the future (ESAP 2009).
The tools of molecular genetics are likely to have considerable impact in the future. For example, DNA-based tests for genes or markers affecting traits that are difficult to measure currently, such as meat quality and disease resistance, will be particularly useful (Leakey 2009). Genomic selection should be able to at least double the rate of genetic gain in the dairy industry (Heins et al 2009), as it enables selection decisions to be based on genomic breeding values, which can ultimately be calculated from genetic marker information alone, rather than from pedigree and phenotypic information.
Furthermore, the large national livestock populations that offer significant potential for genetic improvements in productivity, these in turn will greatly increase total production rapidly rising world-wide demand for cattle products, government well disposed to sector and willing to improve policies and increase budgetary allocations for livestock sub-sector, increase supply of improved local and exotic genotypes through private and community based animal genetic improvement program for targeted interventions(Azage et al 2010; ESAP 2006; Aynalem et al 2011).
The growing demands for reliable services and quality semen, in most cases, users of the AI service are willing to pay even higher fees per service provided that they get quality semen and reliable services, the possibilities of getting alternative semen sources from private organizations, Nationally established system and organization to coordinate crossbreeding efforts, efforts being made by partner GOs and NGOs to improve the service were some important opportunities to implement and improve efficiency and effectiveness of AI service (Desalegn 2011).
Diversified genetic resource permits traditional selection practices of breeding animals within and between populations are also one potential that could lead to gradual genetic differentiation and breed divergence. Adaptation of animals to cope up specific environmental stresses is another force responsible for genetic variations between cattle populations. Genetic variation is key issue for adaptation and selective breeding as result; it is basic tool for future genetic improvement (Dereje et al 2008).
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Received 13 May 2012; Accepted 31 May 2012; Published 1 July 2012