Embodiments herein relate to animal feed preservatives including byproducts containing levulinic acid and methods of making and using the same. In an embodiment, a method of making an animal feed preservative is included. The method can include obtaining an acidic byproduct of a manufacturing process. The acidic byproduct can include at least about 1% by weight levulinic acid or a salt thereof. The method can further include mixing the acidic byproduct with a base to form the animal feed preservative. The animal feed preservative can include at least about 5 wt. % of the acid byproduct. In various embodiments, a method of reducing the amount of mycotoxins formed in an animal feed product during storage is included. In various embodiments, an animal feed preservative or supplement is included. Other embodiments are also included herein.