However, compounds or substances that are effective in vitro do not necessarily work equally in vivo. This kind of divergence in results may be attributed to key factors related to the bioavailability as well as pharmacology of those compounds or substances in the host organism, destruction of active compounds by gut flora metabolism in rumen and different conditions observed in vitro versus in vivo (Chagas and Vieira, 2007; Peneluc et al., 2009). These considerations should be taken into account when developing new anthelmintic agents