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[trade mark sign] 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 3x3x3 factorial arrangement of a completely randomized design. At the 1:500,000 AF:SA ratio Atox® and Novasil[trade mark sign] 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[trade mark sign] 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. In a parallel 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 0.911μg/mL) with 50g Atox®, 150g Mycosorb®, 50g Novasil[trade mark sign] Plus and 4000mL 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, 300mL/cow of the prepared AF:SA complex suspension for a total of 0.447, 0.360, 0.460 and 0.367μg/mL AFB1, respectively for Atox®, Mycosorb®, Novasil[trade mark sign] 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[trade mark sign] Plus and R-SA. Among the used aluminosilicates, Atox® had the lowest RR value compared with Novasil[trade mark sign] 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[trade mark sign] 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.