Why does the excessive inclusion of simple sodium bentonite clay in feed reduce the bioavailability of vital vitamins and trace minerals?

Sodium bentonite is a widely used, highly economical clay binder incorporated into poultry feeds to bind moisture (as a pellet binder) and adsorb polar mycotoxins like aflatoxins. However, bentonite has a highly active, non-selective crystalline structure with a high cation exchange capacity (CEC). The clay particles carry strong negative electrostatic charges on their surface. This negative charge physically attracts and binds positively charged molecules in the gastrointestinal tract. Unfortunately, many essential vitamins (specifically Vitamin $B_1$ thiamine, $B_2$ riboflavin, and Vitamin A) and divalent trace mineral cations (such as zinc $Zn^{2+}$, manganese $Mn^{2+}$, and copper $Cu^{2+}$) carry these exact positive charges. When bentonite is added to feed at high rates (above 1.0%), it non-selectively adsorbs these vital nutrients, creating insoluble complexes that are excreted in the feces. This reduces the dietary bioavailability of the minerals, leading to sub-clinical leg weakness and vitamin deficiencies. Using low-inclusion, modified binders is critical. Farmers can read mineral adsorption science in the Poultry Encyclopedia, buy certified selective binders on Poultry Plaza, monitor daily feed rates on Poultry Rates, and list healthy flocks on Murghi Mandi.