Microencapsulated immunoglobulin Y and lactic acid bacteria improve intestinal health in Yanbian Yellow calves

Objective: Neonatal calf diarrhea remains a major cause of morbidity and growth impairment, highlighting the need for stable and effective antibiotic alternatives that can simultaneously suppress enteric pathogens and improve gut health.We aimed to develop microcapsules containing immunoglobulin Y (IgY) and mixed lactic acid bacteria (LAB), termed IgY-LAB-MCs, and to evaluate their efficacy and optimal dosage as an alternative strategy for preventing calf diarrhea.Methods: IgY concentrations of 0, 30, 60, and 90 mg/mL were screened with mixed LAB based on bacterial growth and antibacterial activity.IgY-LAB-MCs were prepared using a sodium alginate/chitosan/sodium alginate triple-coating method.Twenty-four newborn Yanbian Yellow calves were assigned to control (CON), low-dose IgY-LAB-MCs (L-YLAB), or high-dose IgY-LAB-MCs (H-YLAB) groups for 60 d.Growth, nutrient digestibility, diarrhea indices, fecal Escherichia coli (E.coli), immune and oxidative markers, fecal microbiota, and short-chain fatty acids were measured.Results: In vitro, 60 mg/mL IgY combined with LAB showed the strongest inhibition of E. coli and Salmonella.IgY-LAB-MCs had an encapsulation efficiency of 95.99%, a viable LAB count of 4.37 × 10⁹ CFU/g, a protection rate of 62.07% after simulated gastric treatment, and an intestinal release rate of 97.80%.In calves, L-YLAB improved final body weight, average daily gain, and nutrient digestibility but reduced fecal score and diarrhea incidence compared with CON (P < 0.05).Both doses reduced fecal E. coli counts, but L-YLAB showed better overall effects.L-YLAB increased serum interleukin (IL)-10 and decreased pro-inflammatory and oxidative stress markers (P < 0.05).Microcapsule supplementation reshaped fecal microbiota; L-YLAB enriched Firmicutes, Verrucomicrobia, UCG-005, Christensenellaceae_R-7_group, and Akkermansia, and reduced Bacteroidetes and Prevotella.Both doses increased fecal short-chain fatty acids, with the highest butyrate concentration in L-YLAB. A c c e p t e d A r t i c l eConclusion: Daily supplementation with L-YLAB improved growth, nutrient digestion, diarrhea status, immune-oxidative balance, gut microbiota, and butyrate production in calves.