Young animals such as calves may be fed milk replacers containing soy havingbeen preserved through treatment with acid-producing bacteria that reduces apH of themilk replacer through microbial digestion of sugars present in soy to therebyproduce afermented milk replacer. The milk replacer is edible for at least 48 hours anditsdigestibility in the young animals is increased due to the microbial digestionof sugars inthe soy that are otherwise indigestible in the gut of the young animals. Thefermentedmilk replacers may be ingested by young animals in group settings. Inaddition, the milkreplacers containing soy may be treated with enzymes adapted to hydrolyzecomplexindigestible carbohydrates within the milk replacer, potassium sorbate orboth. Feedingsystems incorporating these fermented milk replacers may result in increasedgain andincreased dry matter intake without negatively affecting animal health.