The invention relates to a food additive for animals comprising a magnesium phyllosilicate, having a specific surface area of between 50 and 160 m2/g, a cation exchange capacity of between 30 and 170 meq/100 grams, and an intrinsic pH of between 6.5 and 11 in an amount ranging from 31.2% to 98.2% by weight with respect to the total weight of the additive； activated with at least one sodium-containing buffering agent, in a proportion of between 1.8% and 68.8% by weight relative to the total weight of the additive. This additive may also contain a larger amount of buffering agent and/or alkalizing agent. The invention also relates to the method for obtaining and using the additive as a ruminal pH regulator and as a food supplement.
