The inclusion of various organic acids or their salts to diets improves the growth performance of pigs and helps in preventing scouring and high mortality post-weaning. The beneficial effects of organic acids on growth performance are evident within the first few weeks of weaning, and the influence gradually decreases as the pig grows old. Diet acidification significantly reduces the diet pH, but does not affect the gastrointestinal pH. The use of acids in diets for pigs enhances the nutrient digestibility and dissimilarly affects the microbial populations in different parts of the digestive tract.