Effect of combinations of organic acids in weaned pig diets on microbial species of digestive tract contents and their response on digestibility

The effect of combinations of organic acids on digestive microbial population and total tract digestibility of piglets was studied. Thirty 19-21 days weaned pigs (5.4 +/- 0.23 kg, six pigs per treatment) were given a mixed feed with 10 ml water/kg (CTL) or 200 mEq/kg of formic acid (FOR), 1:1 formic:fumaric (FOFU), 1:1 formic:lactic (FOLA) or 2:1 formic:lactic (2FOLA). After 6-8 days, animals were slaughtered. In gastric contents, pH was higher (p = 0.01) with FOFU and lactobacilli tended (p = 0.08) to be lower with FOFU than CTL and FOLA, but coliform counts did not differ (p = 0.14). Acetate proportion was lower (p = 0.03), and propionate (p = 0.05) and butyrate (p = 0.01) higher, with FOFU than CTL, FOLA and 2FOLA. Intestinal coliform counts were higher (p = 0.03) with CTL than FOLA and 2FOLA, but there were no differences on lactobacilli. In intestinal contents, acetate tended (p = 0.06) to be lower with FOR than FOLA and 2FOLA, and butyrate was higher (p = 0.001) with FOR. Although not significantly, dry matter digestibility was 0.03-0.05 lower with CTL than with the other treatments. Combinations of organic acids in piglet diets modify gastric and intestinal microflora, the mixtures of formic:lactic appearing as the most interesting.