Effect of dietary inclusion of benzoic acid on mineral balance in growing pigs

The objective of this study was to determine the effect of dietary inclusion of benzoic acid on utilization of the macrominerals Ca, P, Mg, K, Na, and Cl in growing pigs. Eighteen barrows, initial BW of 28 ± 1.7 kg, were assigned to 3 diets: a basal diet based on barley, wheat, soybean meal, corn, and field pea and formulated to contain 9.31 MJ NE kg^− 1 and 8.84 g^− 1 kg standardized ileal digestible lysine, or the basal diet containing 10 or 20 g kg^− 1 benzoic acid by replacing tapioca starch. The pigs were fed the experimental diets a rate of 2.7 times the maintenance requirement for ME for 21 days. Faeces and urine were collected quantitatively from days 11 to 21, and blood and plasma was collected on days 1, 10, and 21. On day 21, the pigs were killed and the left femur was removed. Benzoic acid linearly decreased (P = 0.001) the urine pH from 7.32 to 5.32, and quadratically increased (P < 0.05) blood pH on day 21. Benzoic acid linearly increased (P < 0.05) the apparent total tract digestibility (ATTD) of Ca, P, and Na from 65 to 72%, 46 to 55%, and 78 to 90%, respectively, linearly decreased (P < 0.05) the ATTD of Cl from 94 to 93%, and did not affect the ATTD of Mg and K. Benzoic acid linearly increased (P < 0.05) the retention of Ca, P, and K from 58 to 67%, 46 to 54%, and 31 to 38%, respectively, linearly decreased (P < 0.05) the retention of Na and Cl from 57 to 48% and 75 to 44%, respectively, and did not affect retention of Mg. On day 21, benzoic acid linearly increased (P = 0.001) plasma P and quadratically increased (P < 0.05) plasma K or tended to increase (P = 0.05) plasma Na. Benzoic acid linearly reduced (P < 0.05) the concentration of ash in femur but not the amount of ash, reduced (P < 0.05) the concentration of Ca and Cl in femur ash, and linearly increased (P < 0.05) the concentration of P in femur ash. In summary, benzoic acid increased the utilization of dietary Ca, P, and K, did not affect the utilization of dietary Mg, and reduced the utilization of dietary Na and Cl. During swine feed formulation, effects of benzoic acid on macromineral utilization should be considered to ensure that macromineral requirements are met and not exceeded following benzoic acid supplementation.