The effects of rumen fluid on the in vitro aflatoxin binding capacity of different sequestering agents and in vivo release of the sequestered toxin

In an in vitro experiment, aluminosilicates (Atox® and Novasil™ Plus) and a yeast cell wall derivate (Mycosorb®) were used as sequestering agents (SAs) to verify their capacity for binding aflatoxin B1 (AFB1) in vitro. SAs were individually mixed at three different ratios with AFB1 (1:5000, 1:50,000 and 1:500,000, w/w) in water (CTR), rumen fluid from a lactating cow with a low rumen pH (LRS) or rumen fluid from a dry cow with a high rumen pH (HRS), and then used in a 3 × 3 × 3 factorial arrangement of a completely randomized design. At the 1:500,000 AF:SA ratio Atox® and Novasil™ Plus sequestered over 0.87 and 0.98 of the AFB1 in the CTR and rumen solutions (LRS and HRS), respectively. This efficacy decreased when the amount of clays was reduced, with higher values (P<0.001) for Atox® compared with Novasil™ Plus (0.50 vs. 0.28 in CTR; 0.58 vs. 0.16 in LRS and 0.44 vs. 0.27 in HRS). Mycosorb® had a lower sequestering efficacy (P<0.001) in all of tested experimental conditions, with 0.34 being the maximum value obtained in the CTR solution. arallel in vivo experiment, complexes between AFB1 and SAs (AF:SA) were obtained by mixing one litre of AFB1 contaminant solutions (0.845, 0.790, 0.832 and 0.911 μg/mL) with 50 g Atox®, 150 g Mycosorb®, 50 g Novasil™ Plus and 4000 mL rumen fluid, respectively. The unbound AFB1 was eliminated from the AF:SA complexes after centrifugation and washing of the precipitates. The strengths of the complexes were investigated in vivo by measuring both the aflatoxin M1 (AFM1) levels and the AFB1 recovery rate (RR) in milk from cows administered through the esophagus, before the morning meal, 300 mL/cow of the prepared AF:SA complex suspension for a total of 0.447, 0.360, 0.460 and 0.367 μg/mL AFB1, respectively for Atox®, Mycosorb®, Novasil™ Plus and contaminated rumen fluid (R-SA). When the prepared AF:SA complexes were given to cows, differences (P<0.05) were observed for the total excreted AFM1, with amounts (ng) of 199, 870, 2394 and 1056, respectively, measured for Atox®, Mycosorb®, Novasil™ Plus and R-SA. Among the used aluminosilicates, Atox® had the lowest RR value compared with Novasil™ Plus (0.002 vs. 0.017; P<0.05), however this was not different to Mycosorb® or R-SA. Higher levels (P<0.05) of AFB1 were released from the Novasil™ Plus AF:SA complex compared with the Atox® complex. R-SA showed a sequestering activity and a low release of the sequestered AFB1 from the AF:SA complex.