Intestinal microorganisms are essential for maintaining homeostasis, health, and development, playing a critical role in nutrient digestion, growth, and exercise performance in pigeons. In young pigeons, the gut microbiota is primarily acquired through pigeon milk, meaning the microbial composition of parent pigeons directly influences microbial colonization in squabs. However, research on the correlation between the gut microbial diversity of parent pigeons and their offspring remains scarce. This study investigates the fecal microbiota and metabolites of 10 pairs of parent pigeons and 20 squabs raised under a 2 + 2 system. Fecal samples were collected at 15 days of age, and differences in the microbiota and metabolites between the two groups were analyzed using 16S rRNA sequencing and LC-MS/MS. The results showed the following: (1) Squabs exhibited significantly lower α diversity, with a reduction in their Chao1 index and observed OTUs compared to the parent pigeons. (2) Firmicutes dominated the fecal microbiota in both groups, but parent pigeon feces showed a notably higher abundance of Proteobacteria. At the family level, 10 distinct families were identified, with 9 at the genus level and 4 at the species level. (3) A LEfSe analysis identified 16 significantly different bacterial species in the parent pigeons and 7 in the squabs. Functional gene abundance was highest in the metabolism, genetic information processing, and environmental information processing pathways. (4) An LC-MS/MS analysis in cationic mode identified 218 metabolites, with 139 upregulated and 79 downregulated in the squabs relative to the parents. These metabolites were primarily concentrated in five functional categories and enriched in 33 pathways, 2 of which showed significant differences. In conclusion, significant differences in both the α and β diversity of fecal microbiota were observed between squabs and parent pigeons, with similar bacterial species but marked differences in abundance. Metabolite analysis revealed greater richness in the parent pigeon feces. These findings suggest that future gut modulation using beneficial bacteria, such as probiotics, could potentially enhance host health based on microbial and metabolite compositions.

Plant polysaccharides, such as Astragalus polysaccharide (APS) and Glycyrrhiza polysaccharide (GPS), have potential as functional feed additives. This study investigated the effects of dietary APS and GPS on growth-related traits, serum biochemical and immune indices, antioxidant capacity, intestinal health, and microbial diversity in early-weaned squabs. A total of 192 15-day-old Silver King squabs were randomly divided into four groups: the control group (CK), the 800 mg/kg APS group, the 450 mg/kg GPS group, and the APS + GPS combination group (AG group), with 12 replicates per group and 4 squabs per replicate. The experiment lasted for 28 days. The results showed that final body weight tended to be higher in the APS, GPS, and AG groups, whereas breast width and breast depth were significantly increased in the GPS and AG groups (p < 0.01). The GPS and AG groups exhibited increased serum immunoglobulin A (IgA; p < 0.05) and immunoglobulin G (IgG; p < 0.01) levels, as well as reduced levels of pro-inflammatory cytokines, including interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α; p < 0.01). All treatments increased serum total antioxidant capacity (T-AOC; p < 0.01), while the AG group reduced malondialdehyde (MDA) levels and increased total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) activities (p < 0.01). Duodenal and jejunal T-AOC increased in all treatment groups (p < 0.01), and APS and AG increased ileal T-AOC (p < 0.01). However, intestinal MDA concentrations increased in several segments, indicating a complex and segment-specific oxidative response. The AG group also increased jejunal lipase activities (p < 0.05). Microbiome analysis suggested that Helicobacter was correlated with immune-related indicators, while Lactobacillus was identified as an important core genus in the microbial co-occurrence network. These findings suggest that dietary APS and GPS may regulate immune function, oxidative–antioxidant responses, intestinal function, and gut microbial composition, thereby supporting physiological adaptation in early-weaned squabs.

This study evaluated the effects of graded fermented grape seed (FGS) supplementation in breeding-pigeon diets on the growth performance, immune responses, and redox status of squabs. Forty-eight healthy pairs of Gray King breeding pigeons were randomly assigned to four treatments, with 12 cages per treatment. Breeding pigeons received the experimental diets beginning 7 d before the expected hatch date. The basal diet was supplemented with 0, 10, 20, or 30 kg FGS per 1000 kg of diet (CON, FGS10, FGS20, and FGS30, respectively), and each pair reared three squabs until 28 d of age. Growth performance, carcass traits, meat quality, serum biochemical parameters, immunoglobulins, inflammatory cytokines, and serum and hepatic redox indices were evaluated. FGS supplementation affected body weight at 14 d of age and average daily gain (ADG) from 14 to 21 d and from 14 to 28 d of age (p < 0.05), but did not affect body weight at 28 d of age. FGS30 reduced ADG from 14 to 21 and 14 to 28 d and increased relative carcass yields, immunoglobulin A, G, and M levels, interleukin-10, tumor necrosis factor-α, aspartate aminotransferase, low-density lipoprotein cholesterol, and serum and hepatic malondialdehyde levels, while decreasing hepatic superoxide dismutase and glutathione peroxidase activities. FGS20 and FGS30 increased breast muscle L* values and press loss. FGS20 showed numerical advantages in several production traits, but increased breast muscle press loss and did not improve hepatic redox status. Overall, FGS supplementation in breeding-pigeon diets resulted in stage-specific and dose-related responses. FGS30 may exceed the appropriate inclusion range. Based on the present data, none of the tested supplementation levels can be considered optimal, and the range of 10–20 kg FGS per 1000 kg basal diet requires further validation.

Early-weaned squabs are sensitive to dietary energy–protein supply, but combined effects remain unclear. We tested metabolizable energy (ME; 11.9, 12.2, and 12.5 MJ/kg) and crude protein (CP; 18, 19, and 20%) in 216 15-day-old gray-feathered King pigeon (Columba livia domestica) squabs using a 3 × 3 factorial design. Higher ME increased abdominal fat percentage, whereas CP affected slaughter traits. ME × CP interactions occurred for live weight, liver index, breast and leg muscle quality, and most digestive enzyme activities. At 18% CP, live weight was significantly higher at 12.5 than at 12.2 MJ/kg ME, whereas the opposite numerical trend occurred at 19% CP. Liver index was lower at 18% CP + 11.9 MJ/kg ME than at 18% CP + 12.2 MJ/kg ME. At 12.5 MJ/kg ME, breast muscle a* was lower at 20% CP than at 18% or 19% CP. Enzyme activities were generally highest at 20% CP + 11.9 MJ/kg ME. Targeted 16S rRNA sequencing associated the highest-energy/lowest-protein treatment with Lactobacillus-related taxa, whereas the opposite treatment showed higher diversity and greater contributions of Pseudomonadota- and Enterobacterales-related taxa. Responses were trait-specific; microbial findings represent associations between two contrasting diets.

This study aimed to investigate the effects of thymol supplementation in health care sand on growth performance, serum biochemical parameters, fecal microbial diversity, and fecal metabolites in Grey King squabs. A total of 160 healthy 28-day-old Grey King squabs were selected and randomly assigned to four treatment groups: the CON, 2%Thy, 3%Thy, and 4%Thy groups. Each group consisted of 10 replicates with four squabs per replicate, resulting in a total of 40 squabs per group. Under identical feeding management conditions and dietary nutrient levels, squabs in the CON group received the basal diet plus 5 g of health care sand; those in the 2%Thy group received the basal diet plus 5 g of health care sand containing 2% thymol; those in the 3%Thy group received the basal diet plus 5 g of health care sand containing 3% thymol; and those in the 4%Thy group received the basal diet plus 5 g of health care sand containing 4% thymol. The experiment lasted for 30 days. During the experimental period, the pigeons were housed in cages measuring 45 cm × 50 cm × 60 cm. Each pigeon was provided with 40 g of diet and 5 g of health care sand daily and had free access to water. After Benjamini–Hochberg false discovery rate correction, no significant differences were observed in growth performance, body measurements, apparent nutrient retention, or energy metabolizability among treatments (q > 0.05). However, thymol-supplemented groups exhibited significantly increased serum total antioxidant capacity and superoxide dismutase, glutathione peroxidase, and catalase activities, together with decreased malondialdehyde levels (q < 0.05). Fecal microbiome and metabolomic analyses were restricted to the CON and 3%Thy groups, with the 3%Thy group selected after evaluation of the phenotypic and physiological responses rather than being prespecified before the experiment. These omics comparisons were therefore considered exploratory. No statistically significant difference in overall fecal microbial community composition was detected between the two groups, whereas 17 candidate differential fecal metabolite features were observed. These features were mainly putatively annotated as lipids and lipid-like molecules, organic acids and derivatives, organoheterocyclic compounds, and benzenoids. Among the supplementation levels evaluated, the 3%Thy group showed comparatively favorable numerical responses in several measured parameters and may be considered a candidate level for further investigation. However, the present findings do not establish an optimal thymol supplementation level, and the biological significance of the exploratory fecal omics results requires further validation.