Salmonella Enteritidis (SE) is a significant foodborne pathogen, with chickens serving as its primary reservoir, underscoring the significance on-farm strategies for improving the microbiological safety of poultry products. This study evaluated the prophylactic efficacy of in-feed supplementation with linalool, a generally recognized as safe (GRAS) plant compound, in reducing SE colonization in broiler chickens. A total of 212 day-old broiler chicks were procured, with 192 randomly assigned to eight groups of 24 birds each, and 20 used to verify colonization efficiency post-challenge. The groups included a negative control (no SE, no linalool), compound controls (no SE, fed 1, 1.5%, or 1.8% linalool), a positive control (SE, no linalool), and treatment groups (SE, fed 1, 1.5%, or 1.8% linalool). On day 7, birds were inoculated with approximately 8.0 log 10 CFU of a four-strain SE mixture, and cecal colonization was determined 48 h later. Eight birds per group were euthanized on days 14, 24, and 34 to enumerate SE populations in the cecum, while liver and intestine samples were collected for histopathological analysis. Additionally microbiome analysis of cecal samples collected on days 24 and 34 was performed using 16S rRNA sequencing by Illumina Miseq. Moreover, the effect of linalool on select SE colonization and virulence genes was investigated by RT-qPCR. Results demonstrated that in-feed supplementation with 1.5 and 1.8% linalool significantly reduced SE counts by at least 2.5 to 3.0 log CFU/g cecum at 34 days ( p 0.05), without adversely affecting body weight, feed intake, or feed conversion ratio ( p 0.05). Cecal microbiome analysis showed no major disruptions in alpha or beta diversity due to linalool supplementation, indicating gut microbial stability. Furthermore, linalool at all tested concentrations did not induce histologic changes in liver or intestinal tissues, confirming its safety at the microscopic level. Histopathologic lesion scores in the liver and intestine were significantly lower in the SE + linalool 1.5% and SE + linalool 1.8% groups compared to the positive control ( p 0.05). Gene expression analysis revealed that linalool downregulated the expression of critical SE colonization genes ( p 0.05). These findings suggest that prophylactic in-feed supplementation with linalool effectively reduces SE colonization in broiler chickens without adversely affecting bird health and production parameters.
Viju et al. (Tue,) studied this question.