Bentonite as an arsenic and lead adsorbent in the bovine digestive tract: an in vitro study | Bentonita como adsorbente de arsénico y plomo en el tracto digestivo de bovinos: estudio in vitro

إنجليزي. Objective. To determine the recommended dose of bentonite as a chelator of arsenic (As) and lead (Pb) in the rumen, abomasal and duodenal environment by means of an in vitro system, considering the variables of ruminal fermentation and the adsorbent effect of As and Pb. Materials and Methods. Vials were prepared with 50 mL of anaerobic medium and 0.5 g of alfalfa as substrate. The culture media were added with 1.01 and 1.95 ppm of As and Pb, respectively. The treatments consisted of different levels of bentonite (B) added to the medium, B-0%, B-1.5%, B-3.0% and B-4.5%. The media were incubated for 24 h, and pH, volatile fatty acid (VFA) and N-NH3 production, in vitro DM digestibility (IVDMD) and chelating effect of bentonite were measured, simulating rumen, abomasum and duodenum conditions. A completely randomised design and orthogonal contrasts were used. Results. Bentonite did not modify the pH (p > 0.05) and the molar proportion of VFAs, but the total VFA concentration presented a negative linear effect with increasing bentonite levels. Likewise, the N-NH3 level decreased (p < 0.05) with increasing inclusion levels of bentonite. The IVDMD was reduced with B-3% and B-4.5% (52.36b and 49.74b%) in comparison to B-0% and B-1.5% (62.30a and 61.98a%). Treatments B-1.5% and B-4.5% improved (p < 0.05) As and Pb adsorption in the rumen, abomasal and duodenal environments. Conclusions. The recommended level of bentonite as chelator of As and Pb is 1.5%; doses of 4.5% affect IVDMD and, consequently, animal productivity.

الأسبانية؛ قشتالية. Objetivo. Determinar la dosis recomendable de bentonita como quelante de arsénico (As) y plomo (Pb) en el medio ruminal, abomasal y duodenal mediante un sistema in vitro, considerando las variables de fermentación ruminal y el efecto adsorbente de As y Pb. Materiales y Métodos. Se prepararon viales con 50 mL de medio anaerobio y 0.5 g de alfalfa como sustrato. Los medios se adicionaron con 1.01 y 1.95 ppm de As y Pb, respectivamente. Los tratamientos consistieron en el nivel de bentonita (B) adicionada al medio, B-0%, B-1.5%, B-3.0% y B-4.5%. Los medios se incubaron durante 24 h y se midió el pH, producción de AGV, N-NH3, degradabilidad in vitro de MS (DIVMS) y efecto quelante de la bentonita, simulando las condiciones del rumen, abomaso y duodeno. Se usó un diseño completamente al azar y contrastes ortogonales. Resultados. La bentonita no modificó el pH ni la proporción molar de AGV (p>0.05), pero la producción total de AGV presentó un efecto lineal negativo al aumentar el nivel del mineral.  Asimismo, el N-NH3 disminuyó (p<0.05) al adicionar bentonita. La DIVMS fue menor con B-3.0% y B-4.5% (52.36b y 49.74b%) en comparación con B-0% y B-1.5% (62.30a, 61.98ª). La inclusión de B-1.5% y B-4.5% mejoró (p<0.05) la adsorción de As y Pb en el medio ruminal, abomasal y duodenal. Conclusiones. La proporción de bentonita recomendable como quelante de As y Pb es de 1.5%, ya que la dosis de 4.5% afectan la DIVMS y por consiguiente, la productividad animal.