Methods involve feeding livestock animals a milk replacer, where the milk replacer includes non-milk proteins and phytase. Prior to feeding the milk replacer, the phytase may be activated through heat and moisture treatment. The activated phytase may rest for an activation period and the milk replacer containing the activated phytase may be fed to the animal thereafter. The livestock animals may be calves, and may be between about 0 and about 3 weeks of age. In response to ingesting the milk replacer, the calves may increase a rate of weight gain.
