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.