Described herein are methods and plants for the reduction of harmful byproducts of animal agriculture by biotechnological means. More particularly, the methods described herein use genetic engineering to enhance plant biosynthesis of small, halogenated molecules, including bromoform (CHBr.sub.3), iodoform (CHI.sub.3), chloroform (CHCL.sub.3), or combinations thereof that inhibit enteric methanogenesis in livestock. The plants may include transgenic elements that further relate to targeting engineered metabolism to specific plant tissues and stabilizing specific end products. Such plants can be used as feedstock for ruminant animals.

The present disclosure features a method of modulating production of a small halogenated organic compound with a peroxidase enzyme, and related compositions and methods of use thereof.