Disclosed are methods of administering at least two Bacillus strains to a pig, such as female breeding stock, nursery pigs, or other pigs. The Bacillus strains inhibit Clostridium in litters borne to the pig. The Bacillus strains also are useful when administered to herds lacking symptoms of Clostridium infection. Administration of the Bacillus strains improves performance of female breeding stock and in piglets borne by the female breeding stock.