Effect of Portulaca oleracea Addition in Health Care Sand on Apparent Nutrient Digestibility, Serum Parameters, and Excreta Microbiota Metabolism in Tumbler Pigeons

Tumbling pigeons are prone to oxidative stress and disruption of gut microbiota balance during long-term exercise training and competitions. Considering that <i>Portulaca oleracea</i> (<i>P. oleracea</i>), as a natural plant feed additive, has natural antioxidant, anti-inflammatory, and gut function improvement effects. This study investigates the effects of adding <i>P. oleracea</i> into health care sand on nutrient digestion and metabolism, serum parameters, and excreta microbiota metabolism in tumbler pigeons. Ninety 12-month-old tumbler pigeons were randomly assigned to three groups, with ten cages with three birds each. The CON Group received a basal diet added with 4 g of health care sand; Group TRT1 received a basal diet added with 4 g of health care sand containing 0.75% <i>P. oleracea</i>; and Group TRT2 received a basal diet added with 4 g of health care sand containing 1.00% <i>Portulaca oleracea</i>. The adaptation period lasted for 7 days, followed by a formal testing phase of 45 days. All tumbler pigeons received 1 h of flight training daily. The CON and TRT2 groups showed significantly increased dry matter (DM) apparent digestibility by 11.68% (<i>p</i> < 0.01) and 8.50% (<i>p</i> < 0.05), respectively, compared to the TRT1 group. The TRT2 group also demonstrated higher organic matter (OM) apparent digestibility (increase of 4.25%, <i>p</i> < 0.05) and markedly improved crude protein (CP) digestibility (16.72% higher than CON, <i>p</i> < 0.05; 27.12% higher than TRT1, <i>p</i> < 0.01). Both gross energy (GE) and metabolizable energy (ME) digestibility were significantly elevated in CON and TRT2 groups compared to TRT1 (<i>p</i> < 0.01). Compared to the CON group, the TRT2 group showed a 19.86% decrease in lactate (LAC) level (<i>p</i> < 0.05) alongside a 38.91% increase in lactate dehydrogenase (LDH) activity (<i>p</i> < 0.05). Serum uric acid (UA) levels increased by 33.65-36.14% in both treatment groups (<i>p</i> < 0.05). Antioxidant capacity markedly improved, with malondialdehyde (MDA) decreasing by up to 27.75% (<i>p</i> < 0.01) and key antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and total antioxidant capacity (T-AOC) showing dose-dependent enhancements of up to 25.23% (<i>p</i> < 0.01). Other serum biochemical parameters showed no significant differences (<i>p</i> > 0.05). Microbial analysis demonstrated that Actinobacteriota, Acidothermaceae, and Nitrosotaleaceae were enriched in the TRT1 and TRT2 groups, while the relative abundance of Proteobacteria and Chitinophagaceae decreased (<i>p</i> > 0.05). Metabolomic analysis revealed a significant increase in beneficial metabolites, including agmatine, pyropheophorbide-a, and <i>N</i>-acetylmuramate (<i>p</i> < 0.01). In conclusion, the addition of 1.00% <i>Portulaca oleracea</i> in health care sand effectively enhanced apparent nutrient digestibility, improved antioxidant capacity, and modulated the intestinal microbiota and metabolic profile of tumbler.