Genetic selection for high growth performance has markedly improved poultry production efficiency. However, gastrointestinal responses to selection for high body weight (HBW) remain poorly characterized. In this study, ten chickens from each of the primitive and HBW lines of Lueyang Black-boned chickens were monitored for growth performance from 1 to 180 days of age, and gastrointestinal morphology and microbial composition were compared at 180 days. Gastrointestinal structural traits were analyzed using t-tests, whereas microbial profiles were evaluated using non-parametric statistical methods. Compared with the primitive line, the HBW line exhibited: 1) Growth performance: no differences in body weight at 1 and 45 days, but significantly higher at 120 (39.82%) and 180 days (29.17%) (P < 0.05), along with a significantly lower feed conversion ratio during 45-120 days (10.17%) (P < 0.05); 2) Serum parameters: increased serum biomarkers associated with lipid transport (P < 0.05), with upward trends in glucose and uric acid concentrations (P < 0.10); 3) Organ morphology: increased weights of the crop (35.93%), gizzard (30.90%), duodenum (46.07%), cecum (33.80%), pancreas (32.74%), and liver (38.11%) (P < 0.05), while glandular stomach weight remained unchanged; and elevated villus height-to-crypt depth ratios in the duodenum (130.18%) and ileum (40.95%) (P < 0.05). 4) Microbial alterations: Segment-specific microbial alterations indicated an adaptive pattern characterized by enhanced nutrient utilization but attenuated immune-related functions. Specifically, enriched nutrient-associated taxa included crop Enterococcus and Bacillus, duodenal Lactobacillus, ileal Enterococcus, and cecal Bacteroidales. In contrast, immune-related functional shifts were characterized by crop xenobiotic biodegradation pathways, suppressed duodenal Salmonella- and immune-related signaling pathways, altered ileal alanine, aspartate, and glutamate metabolism, and cecal isoquinoline alkaloid and peptidoglycan biosynthesis pathways. Collectively, this study demonstrates that genetic selection for HBW has driven enhanced nutrient utilization in the gastrointestinal tract while attenuating microbiota-related immune functions, thereby providing a theoretical basis for precision nutrition strategies in poultry.
Keywords: Lueyang Black-boned chicken; gastrointestinal morphology; genetic selection; high body weight; microbiota.
Genetic selective breeding has greatly increased the growth rate of modern chickens, improving global food production efficiency. However, its effects on the digestive system are not fully understood. In this study, we compared a traditional chicken line with a line selectively bred for high body weight. Growth was monitored from hatching to adulthood, and digestive organ development and gut microbial communities were examined at maturity. Chickens selected for higher body weight grew faster in later stages and converted feed more efficiently. They showed larger digestive organs and improved intestinal structure, suggesting enhanced capacity for digestion and nutrient absorption. Distinct differences were also observed in microbial communities across intestinal regions. These microbial patterns were associated with greater potential for nutrient utilization, while immune-related functions appeared reduced. Overall, long-term selection for high body weight was associated with adaptive changes in both digestive organs and gut microbial composition, providing insight into how breeding strategies influence gut biology and production performance.
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