Probiotics have gained attention as alternatives to antibiotic growth promoters in broiler production due to their ability to support gut health, immune function, and disease resistance. Bacterial chondronecrosis with osteomyelitis (BCO) is a major cause of lameness in broiler chickens and is commonly associated with bacterial translocation from the gastrointestinal tract. Strategies that improve intestinal integrity and host responses may help mitigate this condition. This study evaluated the efficacy of a probiotic program comprising an Enterococcus faecium-based spray (2 × 10⁹ CFU/bird at hatch) and a triple-strain Bacillus-based feed additive (B. subtilis 597, B. subtilis 600, and B. amyloliquefaciens 516 at 500 g/t feed from day 1 to 56), applied alone or in combination. A wire-flooring challenge model was used to simulate BCO transmission. A total of 1,560 Cobb 500 broilers were randomly assigned to four treatment groups: NC (negative control, 6 replicate pens), GalliPro® Hatch (E. faecium spray only, 6 replicate pens), GalliPro® Fit (Bacillus-based feed supplement only, 6 replicate pens), and Hatch/Fit (combined treatment, 6 replicate pens). Two additional wire-floor seeder pens served as the infection source for the BCO challenge. Tight junction gene expression (CLDN1, CLDN5, OCLN, ZO-1, and ZO-2) was assessed in the ileum and trachea at d 7, 28, and 56, along with serum IgM, IgA, and serotonin concentrations. Probiotic supplementation significantly influenced ileal gene expression, with significant effects of treatment, age, and treatment × age interaction for selected tight junction genes (P < 0.05). OCLN and ZO-1 were upregulated at d 7 (P< 0.001), followed by sustained increases at d 56, particularly in the Hatch/Fit group (p < 0.05). Tracheal responses were variable. Plasma IgA concentrations increased with age (P < 0.001), reflecting normal immune maturation. Notably, serum serotonin concentrations were markedly elevated in the Hatch/Fit group, indicating microbiota-driven modulation of the gut-brain axis. Bacterial isolation identified a polymicrobial profile dominated by Staphylococcus spp. Collectively, these findings demonstrate that combined probiotic supplementation modulated tight junction gene expression and serum serotonin concentrations in BCO-challenged broilers. These results support evaluation of combined probiotic strategies in commercial production systems.

This experiment compared 14-day and 28-day inclusion schedules of 1,25(OH)₂D₃-glycosides in the broiler feed on the reduction of experimental clinical bacterial chondronecrosis with osteomyelitis (BCO) lameness, using the aerosol transmission induction model. Eight hundred and forty Cobb 500 chicks were randomly allocated to each of the following treatments at 60 chicks/pen as the initial stocking density and reared over 56 d: T1 (Positive Control-PC, 2 wire-flooring pens)—Basal diet (7166 IU/kg Vit-D3); T2 (Negative Control-NC, 4 litter pens)—Basal; T3 (4 litter pens)—Basal + 14d 1,25(OH)₂D₃-glycosides (1 µg/kg feed); and T4 (4 litter pens)—Basal + 28d 1,25(OH)₂D₃-glycosides (1 µg/kg feed). There were three feeding phases: Starter (d0–21), Grower (d22–42), and Finisher (d43–56). Clinical lameness assessment was conducted daily from d21, followed by euthanasia and necropsy of clinically lame birds to determine BCO lesion severity. Cumulative lameness incidence rates between treatments were assessed using binomial logistic regression analysis in a generalized linear mixed model. All statistical significance was determined at p < 0.05. Cumulatively, T4 (55.5%) was significantly lower in clinical lameness incidence compared to T2 (85.0%, relative decrease of 34.71%; p < 0.0001), while T3 (85.5%) was not significantly different (p = 0.89). These results further affirm efficacy of the 28-day inclusion period and the rate of 1,25(OH)₂D₃-glycosides against experimental clinical BCO lameness incidence.

Background/Objectives: Antimicrobial resistance (AMR) in Staphylococcus spp. associated with poultry production is an emerging concern with implications for animal and public health. This study aimed to characterize antimicrobial susceptibility patterns and detect targeted methicillin resistance determinants in Staphylococcus isolates recovered from broiler chickens affected by bacterial chondronecrosis with osteomyelitis (BCO). Methods: A total of 200 bacterial isolates were evaluated, of which 167 were confirmed as Staphylococcus spp. Species identification was performed using presumptive phenotypic characterization followed by 16S rRNA gene sequencing. Antimicrobial susceptibility was assessed using disk diffusion, while presumptive methicillin-resistant phenotypes were evaluated using oxacillin screening and CHROMagar MRSA. Targeted molecular detection of mecA and mecC was performed by PCR. Results: The isolates demonstrated substantial species diversity, with S. aureus as the predominant species. Antimicrobial resistance was mainly observed against β-lactam antibiotics, particularly penicillin (33.5%), whereas high susceptibility was retained for non-β-lactam agents, including ciprofloxacin, tetracycline, trimethoprim–sulfamethoxazole, and azithromycin. A targeted PCR detected mecA in 7.2% of isolates, while mecC was not detected. The detection of mecA in oxacillin-susceptible isolates suggested genotype–phenotype discordance. Conclusions: BCO-associated Staphylococcus spp. from broiler chickens showed diverse species distribution, penicillin-dominant resistance, and targeted mecA detection across multiple species, supporting the use of combined phenotypic and molecular approaches for methicillin resistance surveillance.