Effects of Lactobacillus acidophilus and natural antibacterials on growth performance and Salmonella colonization in broiler chickens challenged with Salmonella enteritidis

Abstract

In this study, 2 experiments were conducted to investigate the effects of L..acidophilus (LA) and its combination with natural antibacterials [medicinal plant aqueous extracts (MPAE) and organic acids] in broiler chickens challenged with S. enteritidis (SE). In the first experiment, the antibacterial activities of natural antibacterials against SE and LA were assayed. In the second experiment, the effect of the LA and its combination with Thymus vulgaris. L aqueous extract (TVAE) and acetic acid (AcA) in drinking water of broiler chickens challenged with SE was investigated. A total of 420 one-day-old male broiler chickens were randomly allocated to 7 treatments (5 replicates) consisted of drinking water without additives (Control), drinking water supplemented with 200 mL trimethoprim-sulfadiazine/1,000 L (0.02% TS), drinking water supplemented with 200 g LA/1,000 L (0.02% LA), drinking water supplemented with 5 mL AcA/1,000 L (0.5% AcA), TVAE with 5 mg dried extract/mL (0.5% TVAE), 0.02% LA mixed 1:1 with 0.5% AcA (0.02% LA + 0.5% AcA), and 0.02% LA mixed 1:1 with 0.5% TVAE (0.02% LA + 0.5% TVAE). The experiment lasted for 24 d. Based on the in vitro results, TVAE and AcA were chosen out of MPAE and organic acids, respectively, for having the most inhibitory effects against SE (P < 0.001) but they did not have inhibitory effects on the LA. The results of the second experiment indicated that LA and LA + TVAE improved the body weight gain (P < 0.001), whereas AcA had negative effects on the body weight gain, feed intake, water intake, and feed conversion ratio compared to Control (P < 0.001). On d 8, the LA + TVAE reduced fecal shedding of SE compared to Control (P = 0.02). Furthermore, broiler chickens were received TS, AcA, TVAE, and LA + TVAE had the greater Lactobacillus spp. populations in the ileum (P = 0.02). The inclusion of LA + TVAE decreased SE counts in the cecum on d 15 (P = 0.04). The supplementation of LA, TVAE, and LA + TVAE increased the villus surface area of the jejunum compared to (P = 0.009). Villus height in the ileum (P = 0.001) and jejunum (P = 0.02) was longer for all treatments (except for LA in the ileum) than Control. In conclusion, the LA and its combination with TVAE showed positive effects on the growth performance, intestinal microbial ecology, and gut morphology of broiler chickens and could have the potential to be used as a growth promoter.