Use of ionophores in lactating dairy cattle: A review

Ionophores are feed additives that alter rumen microbial populations throug h ion transfer across cell membranes. Although ionophores have been used wi dely in the beef industry for improved feed efficiency and control of cocci diosis, there has been limited use by the dairy industry. In Canada, the la bel warning prohibiting the use of monensin premix in lactating dairy cattl e was removed in June 1996. Following this, in December 1997, a controlled release capsule containing monensin was approved for use in dairy cattle as an aid to prevent subclinical ketosis. Monensin may have several advantage s for dairy cattle, including improved energy metabolism, increased milk pr oduction, and altered milk components. This literature review was primarily conducted in 1996 by using the Agricola and CAB search databases. Other re levant articles published since the search (up to 1998) have been added. Th is review will provide practitioners with relevant references in the publis hed literature regarding ionophore use in dairy cattle. It should also give Some guidance as to what effects might be anticipated with the use of iono phores in lactating dairy animals.