No abstract

The effects of probiotic supplementation vary among species or strains, and the dose and feeding timeline could alter the intestinal environment of broilers. A fresh culture of Bacillus subtilis CE330 and multiple lactic acid bacteria (LAB) strains was administered to hatched broilers to investigate their synergistic and long-term effects. One-day-old Cobb broilers (n 30) were randomly distributed into five groups (six chicks per group) and orally fed dH 2 O (control), B. subtilis CE330, or mixed cultures of B. subtilis CE330 and LAB at different doses and times. The simultaneous oral feeding B. subtilis CE330 and 4 LAB strains (ratio equal to 1:4) resulted in the best improvements in growth and health performance in broilers raised without antibiotics. The probiotic-fed group showed a 32.3% higher body weight gain and a 30.2% increase in high-density lipids. One of the 22 Bacillus-like isolates showed similar properties to B. subtilis CE330, including inhibition of bacterial pathogens, presence of the subtilosin gene, digestive enzyme activity, and antibiotic susceptibility. PCR-DGGE analysis revealed that the control group exhibited a diverse bacterial population of pathogen-related species that was not detected in the caecum of the B. subtilis CE330-fed group. The villus number and the morphology of the epithelial cells in the caecum were obviously increased and improved the nutrient adsorption in the probiotic-fed groups. The administration of three doses of a probiotic mixture early after hatching was sufficient for a long-term health benefit on broilers. The most effective probiotics could be further developed for the production of antibiotic-free broilers. Keywords Bacillus subtilis • Lactic acid bacteria • Probiotics • Broilers • Caecal villi • PCR-DGGE Abbreviations CA4 Enterococcus faecium CA4 CE330 Bacillus subtilis CE330 CH24 Lactobacillus salivarius CH24 CH33 Enterococcus durans CH33 SH8 Pediococcus acidilactici SH8 BS Bacillus subtilis CE330 B Wilailak Siripornadulsil