The effects of Lactobacillus johnsonii (L. johnsonii) on gut microflora, bird performance and intestinal development were assessed using 288 one-day-old Cobb broilers challenged with Salmonella sofia (S. sofia). The experiment was a 3 × 2 factorial design which consisted of three treatments, a negative control (NC) with no additives, a positive control (PC) containing antimicrobials (zinc-bacitracin, 50 mg/kg) and a probiotic group (Pro), and with the two factors being unchallenged or challenged with S. sofia. A probiotic preparation of L. johnsonii (109 cfu/chick) was administered to chicks individually by oral gavage on days 1, 3, 7 and 12. Chicks were individually challenged with S. sofia (107 cfu/chick) by oral gavage on d 2, 8 and 13. Results showed that the challenge itself markedly reduced (P < 0.05) bird performance and feed intake. And, transient clinical symptoms of the infection with S. sofia were observed from the second time they were challenged with S. sofia in the negative challenge groups. The novel probiotic candidate L. johnsonii reduced the number of S. sofia and Clostridium perfringens in the gut environment, and improved the birds' colonization resistance to S. sofia.
Keywords: Broiler; Challenge; Probiotic; Salmonella sofia.