Excess of dietary benzoic acid supplementation leads to growth retardation, hematological abnormality and organ injury of piglets

• Safety of dietary benzoic acid supplementation in piglets was studied.
• Blood indices at three time points were detected.
• Benzoic acid residues in the liver and kidneys in two periods were detected.
• Excess benzoic acid impaired performance, blood components, liver and spleen structures of piglets.

Benzoic acid has been widely used in feed industry as an organic acidifier and preservative. However, it is unknown whether excessive benzoic acid in diets would have a potential risk on pigs. This study was conducted to investigate the safety of benzoic acid that was used in diets of piglets. A total of 120 weaned pigs [(Yorkshire×Landrace)×Duroc] with initial average BW of 8.16±0.09 kg (28±1 d of age) were randomly allotted to four groups receiving diets supplementing 0%, 0.5%, 2.5% and 5.0% benzoic acid for 56 d. Supplementing 0.5% benzoic acid in the diet had no negative effects on the growth of piglets, and increased antioxidant enzyme (CAT and GSH-Px) activities in the liver (P<0.05). Dietary 2.5% benzoic acid supplementation decreased ADFI and ADG of pigs from 1 to 28 d (P<0.05), reduced the white blood cell and globulin on d 56 (P<0.05), and resulted in spleen injury on d 28 and d 56. In addition, besides impairing growth performance of pigs during the whole experiment (P<0.05), supplementing 5.0% benzoic acid in the diet increased the relative liver weight on d 56 (P<0.05), enhanced the serum alanine aminotransferase and aspartate aminotransferase of pigs on d 28 (P<0.05), and led to liver injury. Moreover, dietary 5.0% benzoic acid supplementation also decreased the red cell pressure product, red blood cell volume and increased red cell distribution width-SD/CV on d 28 (P<0.05), and resulted in the serious spleen damage. When compared with pigs fed by the diet supplemented 0.5% benzoic acid, pigs fed the diets containing 2.5% or 5.0% benzoic acid would have higher benzoic acid residues in the liver and kidneys on d 28 and d 56 (P<0.05). These results suggested that dietary 0.5% benzoic acid supplementation had the beneficial effects on piglets, but supplementing excessive (2.5% and 5.0%) benzoic acid in the diets could lead to growth retardation, hematological abnormality and the injury of some organs (liver and spleen).