A Review of the Effect of Formic Acid and Its Salts on the Gastrointestinal Microbiota and Performance of Pigs

Simple Summary Acidifiers, especially formic acid and its salts, have long been used for improving the gastrointestinal health and growth performance of pigs, especially piglets. Although, some biological mechanisms explaining their effects are already known, a lack of consensus is still reported on their effects on the gastrointestinal microbiome. The present review provides an overview and evaluation of the effects of formic acid and its salts on the gastrointestinal microbiota and on the growth performance of pigs. Abstract Out of the alternatives to antibiotics and zinc oxide, organic acids, or simply acidifiers, play significant roles, especially in ensuring gut health and the growth performance of pigs. Regarding acidifiers, formic acid and its salts have shown very promising results in weaning, growing and finishing pigs. Although it is known that the main mechanisms by which acidifiers can improve livestock performance and health are related to the regulation of gastrointestinal pH, an improvement in intestinal digestibility and mineral utilization, and their antimicrobial properties against specific pathogens has been observed, while poor consensus remains in relation to the effect of acidifers on bacteria and the complex microbiome. Therefore, the aim of the present review was to critically evaluate the effects of formic acid and its salts on the performance and the gastrointestinal microbiota balance of pigs.