The invention provides an animal feed composition comprising microbial a-amylase, for example, an animal feed composition comprising transgenic plant material comprising a microbial a-amylase (e.g., a thermostable microbial a-amylase). The invention further provides methods of increasing animal performance and/or the efficiency of feed utilization by an animal (e.g., for milk or meat production), comprising feeding to the animal an animal feed composition of the present invention.