Summary
Located in Southeast Asia, Vietnam is known as a developing country with a per capita income of USD 2,785.72. In 2020, Vietnam’s population reached 97 millions, of which the rural population accounts for 63.18%. Therefore, agriculture still plays an important role in the development strategy of the nation. Agriculture not only ensures food security for its large populations but also contributes to the country’s economic development. It contributes 14.84% to the gross domestic product (GDP).
Chicken farming sector is important and the annual production of chicken meat is second after pork. Diversity of indigenous chicken in Vietnam is remarkable with about 21 breeds. Husbandry systems using indigenous chicken breeds are common in Vietnam. Over the past decade, Vietnam has adopted many policies for the development of intensive large-scale animal husbandry. Many exotic breeds have entered the country. Indigenous chicken breeds have been neglected for a long time, sometimes leading to extinct breeds, such as for example the Van Phu chicken breed, declared extinct in 2008, an information reaffirmed in 2015. The status of indigenous chicken breeds in Vietnam is vulnerable due partly to low production capacity. Along with this, the shortage of knowledge about husbandry practices, mating management, and the genetic characteristics of these chicken breeds make it difficult to establish conservation strategies.
This thesis studies two breeds of indigenous chickens in Vietnam: the Ho and Dong Tao chickens. The main objective is to provide detailed information of the characteristics of the breeding system, morpho-biometric characteristics, and production capacity of these two breeds. Furthermore, the thesis aims to propose new strategies for the conservation and sustainable use of these two breeds. The hypothesis is that these two breeds are raised in extensive systems, without mating management. This will result in reduced genetic diversity and increased inbreeding. The use of molecular genetic techniques of high-density SNPs can allow distinguishing these breeds.
This thesis is made of seven chapters. The first chapter is a general introduction about the latest updates of agriculture in Vietnam, the development and change of chicken farming in recent years including a general overview of existing chicken production systems and indigenous chicken breeds in Vietnam. The chapter also introduces research on the breeding of indigenous chickens, genetic characteristics of these breeds and conservation programs for indigenous chickens in Vietnam. The second chapter presents the objectives and hypotheses of the thesis.
The third chapter describes the characteristics of Dong Tao and Ho chicken farming systems based on surveys of 120 Dong Tao chicken farming households and 34 Ho chicken farming households. The survey site is the origin of these breeds of chickens, according to the instructions of the Ministry of Agriculture and Rural Development of Vietnam. The 120 breeding households are sampled from a total of 1,640 Dong Tao chicken breeding households at the time of the survey. Samples were randomly selected from all villages in Dong Tao commune, Hung Yen province. The survey sample of 34 Ho chicken breeding households is composed of all Ho chicken breeding households that accepted the survey in Ho communes, Bac Ninh province at the time of the survey. This study shows that Ho and Dong Tao chickens are reared in a backyard system, with small-scale rearing (for Ho chicken, rearing typically with only a few heads per household). In the Dong Tao chicken farms, three different types of breeding systems are visible. Group 1, composed of almost half of the farmers (45.83%), is semi-intensive and tends towards intensive farming. Group 2 consists of 31.67% of farmers is extensive farming, and tends to be semi-intensive. Group 3 consists of the remaining farmers who use extensive farming. These three groups are fundamentally different in terms of area, farm size, management, and husbandry practices. Ho and Dong Tao chicken farmers tend to increase the use of concentrated industrial feed to improve nutrient supply and improve breeding productivity. Although many breeders have tried to improve the breeding system for these two chicken breeds, persistent problems are reported. These two breeds of chickens are spread over a narrow geographic space, husbandry practices and vaccination use are weak, and there is a lack of mating management. These issues relate to the possible results of increased inbreeding in the population, reduced genetic diversity, and the risk of losing these two breeds because their reduced adaptability to changing conditions (for example in the case of a disease outbreak).
The fourth chapter illustrates morpho-biometric characteristics of the two chicken breeds Ho and Dong Tao. This study describes the body dimensions, feather color, tarsi color, beak color, and crest type of Ho and Dong Tao chickens on 165 individuals Ho chickens (42 cocks and 123 hens) and more than 240 individual Dong Tao chickens (200 cocks, 40 hens) at about 28 weeks of age. The identification of the morpho-biometric characteristics of these two chicken breeds is in line with the guidelines of FAO, 2012. This study shows that Ho and Dong Tao chickens have a variety of morpho-biometric characteristics. Hens have colored feathers (wheat color, dark brown and light brown), cocks have two colored feathers (black feathers with blue light, black with bronze light). There are three types of crests including rose, walnut and polka dot. The tarsi of Dong Tao chickens are large and red, which is a special morpho-biometric characteristic that distinguishes this breed from other indigenous breeds of chickens. Ho and Dong Tao chickens have large body size and body weight. The results of the research also concern the diversity of the genetic characteristics of these two breeds of chickens based on the introduced phenotypic diversity. Along with this is the association with poor reproduction and they have difficulty to mate due to their heavy weight and too large tarsi. It is possible to distinguish the two breeds Ho and Dong Tao based on a combination of morpho-biometric characteristics.
The fifth chapter is related to the production capacity of the two chicken breeds Ho and Dong Tao. This study evaluated the growth capacity, reproduction, meat quality and egg quality of these two breeds. The study was conducted on 125 pure indigenous chickens for each breed, Ho chickens: 62 cocks and 63 hens and Dong Tao chickens: 61 cocks and 64 hens. For each breed, the chickens were randomly split into batches of 25 chickens, and their growth capacity was assessed during 28 weeks. The performance on meat productivity and meat quality was carried out from 12 weeks of age (2 individuals: 1 cock and 1 hen for a batch, randomly selected samples), and every 4 weeks until the age of 28 weeks. The reproductive performances of laying hens were measured during 52 weeks on 36 Ho and 36 Dong Tao hens. Each individual was kept in a separate cage to monitor breeding performance, hens were artificially inseminated once every 2 days to collect embryonic eggs for hatching chicks. The hatching process was carried out in an automatic incubator. Egg quality was assessed on 108 eggs for each breed. This study showed that the growth and reproduction performances of Ho and Dong Tao chickens were poor. The feed conversion efficiency of these two breeds of chickens was low compared to commercial broiler breeds. Slaughter age had been shown to affect certain carcass performance characteristics, suggesting that slaughter at 16 to 20 weeks may be better than at the usual age of 28 weeks. We found that productivity, carcass composition and meat quality are different between the two breeds of chickens. The laying performance of both breeds was low, the hatching rate in Ho hens was lower than that of Dong Tao hens. The indicators of meat hardness, max shell strength and yolk rate per albumen of eggs of two breeds of chickens Ho and Dong Tao were interesting. These results suggest research to improve the production efficiency of these two breeds of chickens, as well as research for the use of these two breeds of chickens in the idea of improving the quality of meat and eggs in commercial chicken breeds.
The sixth chapter studies the molecular genetic characteristics of 4 breeds of chickens, including Ho chickens, Dong Tao chickens, Mia chickens, and Mong chickens. This study used a high-density SNP molecular genetics technique to analyze 96 DNA samples, including 28 Ho, 32 Dong Tao, 18 Mia, and 18 Mong. This study presented the genetic differences between the four populations of Ho, Dong Tao, Mia, and Mong chickens. The populations of Ho and Dong Tao chicken were in separate groups, while that of Mong and Mia had been combined. The results of this study also showed that the polymorphim was the lowest for Ho chickens and the highest for Mia chickens. Ho and Dong Tao chickens had a high inbreeding rate, while Mia chickens had the lowest inbreeding rate. The decline in genetic diversity and increased inbreeding of these chicken breeds were consistent with the thesis hypothesis. At the same time, the use of the molecular genetic technique of high-density SNPs makes it possible to distinguish these chicken populations, which is also consistent with the hypothesis posed at the beginning of this thesis.
The results of this thesis have been reported in the seventh chapter, including general discussions, general conclusions, and recommendations for the future. The achievements of this thesis are related to proposals for conservation, exploitation and sustainable development of the two breeds of chickens Ho and Dong Tao. It aims to improve production systems, strengthen mating management and increase the exploitation of these chicken breed.