The health of neonatal calves is critically influenced by early gut health and microbiota development, yet the potential benefits of Lacticaseibacillus paracasei strains in calves remain underexplored. This study evaluated bovine-derived Lacticaseibacillus paracasei subsp. paracasei Q‑1(L. paracasei subsp. paracasei Q-1) supplementation on neonatal calf health. Forty five-day-old neonatal Simmental×local yellow cattle calves were randomly assigned to four groups for a 60-day: control (CON), low-dose (LP, 1× 10⁸ CFU/calf/day), medium-dose (MP, 3×10⁸ CFU/calf/day), and high-dose (HP, 1×10⁹ CFU/calf/day). Growth rate, diarrhoea incidence, serum antioxidant and immune markers, intestinal permeability indices, and ruminal and faecal microbiota profiles were assessed. Relative to CON, probiotic inclusion increased average daily gain, reduced diarrhoea incidence, boosted serum superoxide-dismutase and glutathione-peroxidase activities, elevated IgA and IgG concentrations, and lowered circulating D-lactate and lipopolysaccharide, indicating improved antioxidant status, immunity and intestinal-barrier integrity. Rumen and faecal 16S rRNA profiling revealed greater community evenness and enrichment of fibre-utilising Firmicutes taxa in supplemented calves. Within the tested range, the MP group (3×10⁸ CFU/calf/day) yielded the most consistent benefits. Larger, longer-term field trials are required before routine on-farm adoption is recommended.

To Cite This Article: Zhang B, Wu Z, Xu Y, Tan M, Tian Y, Kang L, Huang C, Liu D, Zhou Y, Song L and Guo J, 2025. Effects of Lacticaseibacillus paracasei subsp. paracasei Q‑1 supplementation on growth performance, gut health and immune function in neonatal calves. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.315