The flehmen response of bulls and cows.

The response of dairy bulls to the urine of cows in various stages of the reproductive cycle was quantified by presenting 200 ml of urine in a stainless steel bowl to the stanchioned bulls for 10 min. Estrous mucus was also presented in the same manner. Sniffs, nose licks and flehmen responses were recorded. Of 15 bulls tested only 7, or 47%, met the criteria of two flehmens in response to estrous urine. Among these bulls, the rate of flehmen was higher to estrous urine 6.1 +/- 1 flehmen/10 min) than to nonestrous urine (3.5 +/- 0.6 flehmen/10 in, paired t = 3.1, P < 0.03). Flehmen duration was also longer in response to estrous urine (6.4 +/- 0.4 sec) than to nonestrous urine (5.7 +/- 0.4 sec, t = 2.65, P < 0.03). There were no significant differences between the sniff frequencies and durations or in the number of licks to estrous and diestrous urine. There were significantly more flehmen responses to estrous urine (7 +/- 1.4 10 min ) than to mucus (2.25 +/- 0.9 10 min , t = 4.75, P < 0.01). The response to water (0.6 +/- 0.3 10 min ) was not different from that to mucus (t = 2.37, P < 0.10). The spontaneous flehmen rate of dairy bulls in their home stalls was 3.2 +/- 0.7 24 h . Although estrous cows did not exhibit flehmen frequently, they did sniff bull urine more frequently (3.6 +/- 0.6 10 min ) than nonestrous cows (1.8 +/- 0.3 10 min , t = 2.4, P < 0.03).