Effects of novel probiotic on growth performance and microbial composition of broiler chickens with 'Salmonella sofia' challenge

The effects of 'L. johnsonii' on gut microflora and bird performance were assessed using 288 day-old Cobb broilers challenged with 'Salmonella sofia' ('S. sofia'). A 3 x 2 factorial design which consisted of three treatments, i.e., a negative control (NC) containing no additives, a positive control (PC) containing antimicrobials (Zinc-bacitracin, 50 ppm; monensin 100ppm) and a probiotic group (Pro) receiving a probiotic via oral gavage; and two factors, i.e., with or without 'S. sofia' challenge. 'L. johnsonii' (10⁹ cfu/chick) was gavaged on days 1, 3, 7 and 12. Chicks were gavaged with 'S. sofia' (10⁷ cfu/chick) on days 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 'C. perfringens' in the gut environment, and improved the birds' resistance to 'S. sofia'.