Two experiments were conducted to examine the effect of benzoic acid in the diet of lactating sows on urinary pH and nutrient digestibility. In the first experiment, three levels of benzoic acid in the diet were tested (0.5, 1.0, and 2.0%), while in the second experiment only one dietary level of benzoic acid (0.5%) was used. In the second experiment, the urinary excretion of benzoic acid and hippuric acid was additionally measured. The digestibility was estimated in experiment 1 with HCl-insoluble ash as a marker and in experiment 2 in a total balance period with collection of urine and faeces over 5 days. Supplementation of benzoic acid reduced the urinary pH in a dose dependent manner. The relationship between benzoic acid intake and urinary pH response was linear. Dietary benzoic acid at a level of 2% increased the digestibility of organic matter, protein, fat and fiber in the diet. In sows fed the diet supplemented with 0.5% of benzoic acid, 64% of benzoic acid ingested was excreted via urine as hippuric acid, the remainder as unmetabolized benzoic acid.

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