Excess Of Dietary Montmorillonite Impairs Growth Performance, Liver Function, And Antioxidant Capacity In Starter Pigs

Montmorillonite (MMT) is widely used as a mycotoxin adsorbent in animal feeds, but its safety remains unclear. This study was conducted to investigate the safety of MMT supplementation in diets fed to starter pigs. A total of 120 32-d-old piglets (initial weight, 8.0 +/- 0.9 kg) were randomly allotted into dietary treatments with graded MMT levels (0 [FS 0], 0.5% [FS 0.5], 1.0% [FS 1.0], 2.5% [FS 2.5], and 5.0% [FS 5.0]) with 6 replicate pens per treatment and 4 pigs per pen. All diets were fed for 28 d. As the MMT level increased, ADG and G:F changed in a linear and quadratic manner, while ADFI was linearly decreased (P > 0.05). Compared with FS 0, ADG, ADFI, and G:F of pigs in FS 1.0 increased (P < 0.05). However, the ADFI in pigs of FS 5.0 was lower than that in pigs of FS 0 (P < 0.05). The relative liver weight activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) changed in a linear and quadratic manner (P < 0.05). Compared with FS 0, pigs in FS 2.5 and FS 5.0 had a greater serum ALT (P < 0.05), while AST activity significantly increased in pigs of FS 5.0 (P < 0.05). Dietary MMT supplementation decreased serum Mg content in a linear and quadratic manner (P < 0.05), while Zn and Cu contents were linearly decreased (P < 0.05). Serum Zn and Cu contents of pigs in FS 0.5, FS 2.5, and FS 5.0 groups were lower than those in the control. Pigs fed with 2.5% and 5% MMT showed hepatic histopathological changes, including swelling, granular and vesicular degeneration, and apparent vacuolar degeneration. In addition, the content of serum total antioxidant capacity (T-AOC) and activity of glutathione peroxidase (GSH-PX) decreased in a linear and quadratic manner (P < 0.05). Compared to the control, 5.0% MMT significantly increased piglets' serum malondialdehyde (MDA) concentration and decreased GSH-PX activity (P < 0.05). T-AOC concentration in the pigs fed 2.5% and 5.0% MMT was lower than that in the control group (P < 0.05). Serum superoxide dismutase (SOD) activity changed in a quadratic manner (P < 0.05). Piglets in FS 1.0 showed a higher SOD activity when compared with the control (P < 0.05). These results indicate that supplementation of MMT higher than 1.0% can negatively affect liver structure and serum mineral content, and 5.0% MMT supplementation would also decrease feed intake, aggravate liver damage, and reduce the antioxidant capacity of starter pigs. Therefore, excess supplementation of MMT is not safe in starter pigs.