text: Measuring the composition of a cow's rumen can also indicate the quality of its feed, a process called a forage analysis.
  Once the cannula is surgically placed, the cow is then allowed to graze for a certain period of time—for example, 30 to 45 minutes, in a 1960 study at the University of Nevada, Reno. Researchers will then remove some or all of the ruminated material through the cannula. Analyzing rumen this way can indicate whether particular grasses on which cows are grazing are nutritionally adequate.