| 報告時間：2025-4-25 |
| 報告地點：Room 407 |
| 指導老師：Chih-Feng Chen |
| 學生：Yi-Ying Chang |
| 摘要 |
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Brown Tsaiya duck is the only laying type duck breed in Taiwan, characterized by small body size, hard eggshells, and resistance to heat and disease. It has long served as the major source for processed egg. Since feed accounts for approximately 80% of egg production costs, the Eastern Region Branch of the Taiwan Livestock Research Institute initiated selection for residual feed consumption (RFC) in 2009, establishing a Selected line (S) and a Control line (C). This study was conducted to evaluate the selection response in these lines. Furthermore, microsatellite markers were applied for genetic monitoring and to establish a mating scheme. After five generations of selection for low RFC, the Selected line exhibited significant reductions in feed intake compared to the base generation (G0) and contemporaneous Control line. In G9, differences in feed intake and RFC between the two lines were –454.5 g and –330.0 g, respectively, indicating a substantial improvement in feed efficiency. However, genetic trends from G0 to G9 revealed a decline in heritability and genetic variance for RFC, accompanied by a shift in genetic correlation with egg mass (EM) from negative to positive. On average, an increase of one genetic standard deviation in RFC corresponded to a decrease of 0.26 genetic standard deviations in EM. By G9, the egg weight of the Selected line was lower than that of the Control line. Therefore, from G9, EM was incorporated as a selection criterion, and a restricted genetic selection index was implemented from G11 to produce G12. This approach effectively mitigated the decline in EM. Genetic parameter estimates for G9–G12 showed a rebound in RFC heritability and a restoration of the negative genetic correlation with EM, indicating that this method can balance improvements in RFC and related traits. Given that long-term selection may reduce genetic diversity and threaten germplasm sustainability, this study applied 11 Brown Tsaiya duck-derived microsatellite markers to perform cross-generational genetic monitoring. Results showed only slight decreases in observed heterozygosity and effective population size in both lines, with no substantial increase in inbreeding coefficients (FIS), although FST revealed gradual population differentiation, suggesting that long-term selection did not lead to severe loss of genetic polymorphism. In 2022, due to culling, the germplasms were reintroduced from the technology-transferred private farm. To maintain genetic diversity of the germplasm, this study developed a mating scheme based on maximal inter-cluster genetic distance by microsatellite markers. Simulation results indicated that this strategy best preserved genetic diversity among subpopulations. In practical application, although a slight decline in genetic variation was observed, the reintroduced populations and their progeny showed no or only mild differentiation from pre-outbreak populations, confirming the feasibility of the proposed mating strategy in maintaining genetic structure. In summary, this study provides the first systematic evaluation of long-term RFC selection response in Brown Tsaiya ducks and establishes a concrete genetic monitoring and management framework for reconstituted poultry populations, offering practical guidance for future poultry breeding and conservation efforts. |
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