COMPARATIVE PERFORMANCE EVALUATION OF GUMZ, RUTANA AND THEIR CROSSES AND DESIGNING CONSERVATION-BASED BREEDING PROGRAM FOR GUMZ SHEEP IN NORTH WESTERN LOWLANDS OF AMHARA, ETHIOPIA

Abstract

Gumz sheep are among the indigenous sheep that contribute to the genetic diversity of Ethiopian sheep genetic resource and it is the only thin-tailed sheep in Ethiopia. However, indiscriminate crossbreeding or extensive use of exotic germplasms is seriously threatening the existence of indigenous populations. The lack of detailed information and understanding about indigenous breeds, including their threat status, is perceived to be the most important hindrance to their conservation and the development of conservation programmes. This dissertation aimed at charactering the existing sheep production systems, identifing traits in relation to the breeding objectives of the community, evaluating the on farm performance of Gumz and Rutana and their crossbred sheep, assessing threat status of Gumz sheep and finally to design sustanible selective breeding program to improve productivity and conservation of Gumz sheep breed. Metema and Quara districts were purposively selected to conduct the study due to accessibility and distribution of the sheep breeds studied. A total of 240 sheep owners from six kebeles and six investment sites (30 smallholders from each kebele and 10 large scale farmers from each investment site) were selected for interviewing by random sampling techniques. In own flock ranking experiment to define breeding obejectives, forty and twenty households from smallholder and large scale systems, respectively, were studied. For monitoring performance, flocks of 30 smallholder households which consisted of Gumz, Rutana and their crossbreds with a total of 152 ewes and 180 lambs were monitored for a period of 12 months. Threat status was assessed using ten indicators adapted from the Food and Agriculture Organization of the United Nations (FAO) recommended list. Village and central nucleus-based schemes with four different scenarios for Gumz sheep breed were modeled and evaluated using ZPLAN computer program to estimate the genetic gain and returns to investment of the alternative breeding schemes. The study revealed that smallholder farmers kept sheep mainly as a source of income, meat and wealth with an index value of 0.43, 0.19 and 0.15, respectively. The main purposes of large scale farmers for keeping sheep were source of cash income (0.57) and investment opportunity (0.22). xvii Sheep flock sizes were 17.25 ± 0.68 and 90.63 ± 5.38 in smallholder and large scale production systems, respectively. Breed composition of smallholder sheep flocks was 7.47 ± 0.28 Gumz, 3.68 ± 0.25 Rutana and 4.52 ± 0.22 Rutana-Gumz crossbred sheep. The corresponding figures for large scale farms were 21.2 ± 1.4, 30.7 ± 1.69 and 24.7 ± 1.47, respectively. Diseases, stock theft and labour shortage in their order of importance were reported as the main constraints of sheep production in the study area. Natural and uncontrolled breeding was more common in smallholder system where as controlled breeding was practiced to get crossbred sheep for market in both systems. Over half (56%) of the smallholder sheep owners practiced mixing of flocks with their neighbours. Direct ranking method showed appearance, coat colour, tail length and fast growth rate are important traits in selecting breeding rams in both systems. For ewes, traits related to mothering ability and multiple births were preferred in smallholder system whereas multiple births and lambing interval were considered as important traits in selecting breeding ewes in large scale system. In own-flock ranking method, reproductive traits were preferred in all breed groups in both systems but it is more pronounced for Gumz ewes. On the other hand, Gumz was rated poorly in comparision to Rutana in terms of body size and growth rate. Genotype of lamb significantly (P< 0.001) affected live weight of lambs at all ages. The average birth weight of Rutana, Gumz and their crossbred lambs were 3.75, 2.86 and 3.38 kg, respectively. Rutana lambs had significantly highest (118.05±2.67 g) daily weight gain whereas Gumz lambs had the lowest (100.21±2.48 g). The daily weight gain of the crosses fell between these values (107.78±2.66 g). The Rutana lambs also gained more (59.01g/day) than the crossbred (52.15g/day) and Gumz (46.34g/day) lambs from weaning to six months of age. Season of lambing had a significant (P<0.01) influence on age at first lambing, ewes lambed in wet season having shorter age at first lambing than those lambed during dry season. Breed had a significant effect on lambing interval in which Gumz ewes (219±3.73 days) had shorter lambing interval than Rutana ewes (283±5.39 days). Lambing interval was also affected significantly by lambing season, sex of lamb, parity of dam and birth type. Results of lamb survival rate showed that survival of Gumz lambs was significantly (P=0.043) higher than Rutana lambs up to weaning ages. Similarly, Gumz lambs were 6.3 times more likely to survive up to yearling age than Rutana lambs (Odds ratio = 6.3; P=0.007). Analysis of breed merit showed that Gumz sheep had lower economic values compared to Rutana and their crossbred sheep where as adaptive traits, such as resistance to diseases and droughts were highly valued for Gumz compared to Rutana sheep. The relative extinction probabilities showed highest extinction xviii probabilities which range 0.995-0.960 in the study area. In general, it can be concluded that the Gumz sheep population was declining in number in the study area due to the presence of more preferred breed (Rutana) by the farmers. However, Gumz breed is a unique genetic resource in Ethiopia and meet the multifaceted roles of sheep for the smallholder farmers. Simulation study on designs of alternative breeding schemes showed that central nucleus-based scheme with nucleus size of 5% of the Gumz population (scheme 3) and village-based scheme with improved lambing distribution (scheme 2) are considered to be more efficient than the alternative schemes of central nucleus-based scheme with nucleus size of 10% of the Gumz population (scheme 4) and village-based scheme with existing lambing distribution (scheme 1) interms of genetic gain and profitability. However, village breeding program was better for genetic improvement and conservation of Gumz sheep as it involves participation of farmers and a one-tier breeding scheme where both genetic improvement and production are carried out in village flocks. The outcome of this study suggested the possibility for Gumz sheep breed improvement and conservation through selective breeding strategy and improved management.