Effects of organic acids with and without a microbial culture on performance and gastrointestinal tract measurements of weanling pigs

In Study 1, 25-day-old crossbred weanling pigs (n = 144) were fed a 20% crude protein maize-soyabean meal basal diet. Supplementation with 1.5% citric acid tended to improve gain and the efficiency of feed utilization (F:G) during the first 4 weeks with no effect during week 5; 1.5% fumaric acid caused smaller and non-significant improvements in gain and F:G. Feed intake was unaffected by organic acids. The pH, chloride ion and volatile fatty acid concentration of intestinal contents from the stomach, jejunum, cecum and lower colon of 27 pigs killed at the end of Study 1 were not significantly affected by dietary organic acids. With the exception of fumarate, the concentration of non-volatile acids was not affected by diet. The stomach and jejunum of pigs given fumaric acid had a greater concentration (P < 0.05) of fumarate than those of pigs given the control and citric acid diets. In Study 2 (n = 192), no interactive effect of dietary fumaric or citric acid with a live microbial culture (Lactobacillus acidophilus) was observed. Fumaric acid supplementation increased (P < 0.03) gain and the microbial culture improved gain (P < 0.08) and F:G (P < 0.02) during the 5 week test; 1.5% citric acid had no effect. In conclusion, the addition of citric or fumaric acid and/or a microbial culture produced inconsistent improvements in gain and F:G, with little effect on intestinal digesta measurements.