On-Farm Control of Salmonella in Pigs 

The effectiveness of the control of Salmonella in pigs on farms relies on targeted interventions that reduce intestinal colonization, pathogen shedding, and the number of asymptomatic carriers entering the production chain. Feed additives, vaccination strategies, and alternative biological approaches are key components of an integrated control program. 

Feed Additives 

The feed represents one of the most strategic intervention points for Salmonella control. The organic acids, including formic, lactic, and propionic acids, as well as essential oils, have demonstrated efficacy against specific pathogens when incorporated into pig diets (Alarcón et al., 2021). Their antimicrobial activity is linked to pH reduction and disruption of bacterial cell membranes. The encapsulated technologies are preferred as they need to reach; however the free acids will be neutralised early on the digestive tract (Suggested read Organic acids and essential oils: how they work, how they differ - Articles - pig333, pig to pork community)   

Other additives such probiotics—including Lactobacillus and Bacillus velezensis—have shown positive effects in farms with Salmonella problems (USDA‑FSIS, 2023a,b). Probiotics reduce pathogen colonization by modifying the intestinal microbiota and enhancing competitive exclusion (Grandmont et al., 2024). However, the efficacy of the responses may vary; some probiotics reduce Salmonella Typhimurium loads in mesenteric lymph nodes without significantly decreasing fecal shedding (Baer et al., 2013). 

The effectiveness of acidifiers depends on pig age and the specific formulation used (Andrés & Davies, 2015). Lactic acid supplementation has been shown to reduce Salmonella infection in growing pigs (Tanaka et al., 2010), while combinations of sodium butyrate with organic acids and essential oils can reduce fecal excretion (Lynch et al., 2017). Notably, mixtures of short‑chain fatty acids, lactic acid, and oregano oil have been associated with reductions in Salmonella levels in ileocecal lymph nodes, feces, and pre‑slaughter intestinal contents (Willamil et al., 2011). 

Vaccination 

The vaccination is an effective tool to reduce Salmonella prevalence and control clinical disease (Denagamage et al., 2007). Several vaccination strategies have been described, including vaccinating sows before farrowing, vaccinating suckling piglets, combining sow and piglet vaccination, or vaccinating pigs at the entrance into the fattening phase (Smith et al., 2018a,b). 

Vaccine efficacy depends on the objective: protecting public health versus controlling on‑farm clinical disease. Vaccines against Salmonella choleraesuis provide cross‑protection against S. Typhimurium and S. Derby, although serotype‑specific vaccines induce stronger antibody responses. Inactivated vaccines can protect against antigenically similar strains, while live vaccines may confer broader cross‑immunity. Autovaccines offer a rapid solution when no commercial vaccine is available. Nevertheless, only the vaccination is insufficient without proper biosecurity, cleaning, and disinfection. 

Conclusions 

Salmonellosis in pigs represents a significant challenge for both animal production and consumer safety; causing economic losses through mortality, reduced performance, and antimicrobial use. The complexity of risk factors demands a comprehensive control strategy, integrating feed hygiene, additives, vaccination, biosecurity, and strict cleaning and disinfection protocols. The effective control requires coordinated action among farmers, veterinarians, slaughterhouses, and regulatory authorities to reduce Salmonella prevalence along the entire chain of production.