A method of monitoring the physiological condition, and/or suitability of animal feed, of ruminant animals, comprising:a. sensing the occurrence of at least a first predetermined type of activity of the animal；b. determining a length of a time period of a first type during which in step a. a sensed first predetermined type of activity has taken place；c. transmitting information about the length of a time period of the first type determined in step b. wherein preferably the transmission starts on a moment in time which depends on the moment in time on which the time period of the first type has ended；d. repeating steps a.-c. for next sensed occurrences of activities of the first predetermined type.
