Background and Aim: Probiotic species have been proven to be beneficial on broiler performance; however, most studies have focused on industrial chickens with fast growth, whereas little information concerning the use of these species on native chickens is available. This study aimed to investigate the effects of probiotics Lactobacillus plantarum (LP) and Bacillus subtilis (BS) on the mortality, growth rate, and carcass characteristics in native Noi chickens challenged with Salmonella Typhimurium.

Materials and Methods: We divided 420 1-day-old Noi chicks into seven different treatment groups (n = 60): negative
control (no S. Typhimurium, no probiotics or antibiotics); positive control (PC, S. Typhimurium infection, no probiotics
or antibiotics); and S. Typhimurium infection and supplementation with LP, BS, LP + BS, enrofloxacin, and commercial
probiotics, respectively. Treatment was for 96 days, and the chicks were orally challenged with S. Typhimurium at 22 days old.

Results: No deaths occurred during the 4 weeks post-infection in the negative control, LP, or LP+BS groups. The PC group had the highest mortality rate (20%). Re-isolation of S. Typhimurium from the liver, spleen, and heart showed reduced bacterial counts at 1 week post-infection in the LP, BS, and LP + BS groups. The lowest body weight gain was observed in the PC group (949 g/bird), and chicks in the LP group gained 1148 g/bird. An improved feed conversion ratio was noted in the groups receiving probiotic supplementation (3.42–3.50 kg feed/kg gain). There was little evidence that probiotics affected carcass percentage and related parameters, such as breast, thigh and drumstick, and wings.

Conclusion: Lactobacillus plantarum or BS dietary supplementation to native Noi broilers resulted in a lower mortality rate and improved body weight gain but did not affect carcass characteristics.
Keywords: Bacillus subtilis, growth, Lactobacillus plantarum, mortality, Noi chicken.