REVIEW: Alternatives to Conventional Antimicrobials in Swine Diets

There is growing concern that the use of antimicrobials in livestock feeding to enhance growth and to prevent disease is leading to increasing numbers of antibiotic-resistant human and animal pathogens. The exact degree of antibiotic-resistant organisms attributed to the use of antimicrobial agents in livestock feeding remains to be proven. Despite the lack of empirical evidence, many restrictions and bans have been placed on the use of antibiotics in livestock feeding in Europe. At present, there are no bans placed on the use of common antimicrobials in swine feeding in the United States. However, many scientists have begun to seek naturally occurring alternatives to antibiotics for commercial use if ever a similar situation arises here in the United States. This paper reviews the published data from natural agents that may serve as alternatives to conventional antimicrobials currently used in swine feeding operations. Specific natural agents such as probiotics, oligosaccharides, spices, and plant extracts that have shown some promise for enhancing growth performance and immune function are discussed. Based on this review of the literature, it appears that the observed beneficial effects of natural alternatives to conventional antimicrobials on growth performance and immune function are inconsistent among studies. Although these natural substances show promise, at present, it does not appear that any one natural remedy is a competitive alternative to conventional antimicrobials for growth promotion in swine feeding operations.