<P> A cannulated cow or "fistulated cow" refers to a cow that has been surgically fitted with a cannula . A cannula acts as a porthole - like device that allows access to the rumen of a cow, to perform research and analysis of the digestive system . The practice can be traced back to as early as the 1920s . </P> <P> A forage analysis can take place due to the access of the rumen through a cannula . Once the cannula is surgically placed in the cow, a cow is then allowed to graze for a certain period of time . Once the allotted time is up, the material that is located in the cannula is collected and tested . This analysis shows producers which forages are optimal for the use of their individual operation . </P>

What is the point of a fistulated cow