The presently disclosed subject matter relates to feed additive formulations for monogastric animal feed. Particularly, the disclosed formulations comprise an isolated xylanase enzyme and a B. licheniformis strain PWD-1. The feed additive formulations may further include B. amyloliquefaciens strain Ba-BPD1. The disclosed formulations are useful for addition to feeds for monogastric animals to synergistically improve the performance of the animals.