| 口試日期：2026 |
| 學位類別：碩士 |
| 指導教授：陳洵一 |
| 研究生：陳普揚 |
| 摘要 |
| Antibiotic growth promoters (AGPs) have been banned in many countries due to the concern regarding antimicrobial resistance. Consequently, various alternatives, including enzymes, probiotics, and postbiotics, which merit enhancing animal health and production performance, have been widely studied. In contrast to probiotics, postbiotics are non-viable substances, offering greater stability during storage and processing allowing for easier standardization in production, while probiotics may translocate into the bloodstream and potentially cause bacteremia or sepsis, making postbiotics safer alternatives. Postbiotics contain various bioactive components and can effectively inhibit pathogen growth by lowering intestinal pH and improve poultry health and performance through modulations of physiological metabolism, immune responses, and intestinal mucosal environments. This study aimed to evaluate the effect of dietary supplementation with postbiotics from Lactobacillus plantarum (LP) and Pediococcus pentosaceus enriched with GABA (γ-aminobutyric acid) on growth performance, tracheal histomorphology, respiratory barrier function, breast meat quality, hepatic IGF-1 (Insulin-like growth factor-1) expression, and excreta nitrogen wastes in broiler chickens. The study was designed as the basal diet as a control (Con) group, supplementation with GABA 10 or 20 ppm, Postbiotics (POST)(L. plantarum + P. pentosaceus) (LP), SYNLAC probiotics, POST+Bacillus probiotics (BA). The results showed that most treatment groups exhibited improved growth performance as compared with the control group, with the POST(LP) group demonstrating the most pronounced effects. At age of 35 days, these groups showed higher final body weights and body weight gains, along with improved feed conversion ratios, indicating enhanced growth efficiency and feed utilization. In respiratory tract health, all treatment groups exhibited differentially improved tracheal histomorphology such as cilia structure, mucin irritation, and leukocyte infiltration. Furthermore, Occludin expressions were higher in GABA20, GABA10, POST(LP), and SYN group, suggesting improved integrity of the respiratory epithelial barrier. In meat quality, POST(LP) and SYN group showed lower lipid oxidation and better performance in water-holding capacity, and tenderness. At the molecular level, hepatic IGF-1 protein expression was elevated in all treatment groups, indicating that postbiotics and GABA enhance growth potential through the regulation of growth-related signaling pathways. In excreta composition analysis, control birds exhibited higher proportions of total nitrogen, ammonia, uric acid, and urea, whereas the POST(LP), SYN, and POST(BA) group showed relatively lower levels. These findings suggest improved dietary protein utilization and reduced nitrogen excretions. In conclusion, POST(LP) postbiotics can serve as an effective feed additive to improve growth performance, and furthermore potentiate the respiratory system health and thereby may benefit birds against respiratory pathogens, providing promising alternatives to AGPs in poultry production. Keyword: Postbiotics, Broilers, Lactobacillus plantarum, Pediococcus pentosaceus ,Growth performance, Respiratory tract health, Meat quality. |