Ruminants possess a unique digestive system. Using the high metabolic potential of the symbiotic microflora of the rumen, ruminants are capable of digesting plant material and obtaining nutrients and energy from this process. Because of the ruminal fermentation, the most bioactives are not stable in the harsh ruminal environment. Therefore there is a need to improve the bioavailability of a bioactive by protecting it from the ruminal digestion. The formulation of protected bioactive can be delivered in the rumen in a controlled manner and over a long period of time. In this project the degree of rumen protection was estimated using model substrates (sugar pellets and granules). These materials were coated with the pH-sensitive polymer Eudragit E. The model bioactive (phloridizin) was coated using the coating methodology adopted from exploratory studies with model substrates. The bioavailability of protected (coated) phloridizin was assessed by administering directly into the abomasum of fistulated cows. Formulation of protected phloridizin was used to demonstrate the feasibility of bioactive controlled delivery based on ART ( Active Rumen Technology ). This technology uses an elevated gas pressure created by a hydrogen-producing cell to drive a plunger which extrudes bioactive formulation from an intraruminal controlled-release device. Four groups of devices filled with formulation containing different amounts of protected phloridizin were tested. The bioactive was released in a controlled manner over several days. The formulation release profiles were reproducible suggesting that in principle the technology can be further developed to use in a commercial sense or for research purposes. The limitations of the technology, including formulation issues and gas diffusion through barrel walls, were identified.