Feromoninnehållande substansers inverkan på hjärtfrekvensen hos tjur

During the last 50 years the production of milk per cow has increased. This has, however, been followed by a decreased reproductive performance. Shorter and more indistinct signs of oestrus make it harder for the Swedish farmers to discover when the cows are in oestrus. There is a need for ways to control reproduction. The use of pheromones could possibly provide means to satisfy this need. However, this requires a fast and simple in vivo-method for identification of substances containing pheromones. The aim of this study was to investigate whether a change in the heart rate of bulls is possible to use as an indicator, a so-called bioassay, for fast identification of pheromones in body fluids. Two bulls were exposed to the following substances; oestrus mucus and -urine, luteal phase urine, bull urine and water, during intervals of ten minutes. During the exposures each bull had a cassette containing a tampon, with the substance in question, attached to their nose rings. Between every exposure a blank cassette containing only a tampon without substance was attached to the nose rings. During the exposures the heart rates of the bulls were recorded and registered every fifth second. Meanwhile the behaviour of the bulls, with regard to flehmen, erection, secretion and urination, was continuously recorded. The substance oestrus mucus showed, in comparison with the rest of the substances as a whole, an increased standard deviation in heart rate (p<0,05) that was found during the first minute of exposure (p=0,001). During this minute, also the mean heart rate was higher (p<0,05) than for the other substances. There was however no significant difference in mean heart rate or deviation (per minute) between the tested substances. The statistically significant increase in heart rate- and deviation during the first minute of exposure for oestrus mucus, compared to exposure for the others, however, clearly indicates a reaction for oestrus mucus. The fact that the two bulls were sexually inexperienced since they had not met any females since before onset of puberty, has likely had effect on the results. During the study, bull A had erection eleven times and bull B twice. During the majority of these erections only a small part of the penis was detectable. However, during the second day bull A showed a nearly 2 minute's long erection where a large part of penis was exposed. This happened during exposure for a blank cassette. The erections during the study tended to happen randomly, but maybe slightly more often when exposed to bull urine. However, the number of occasions where erections was recorded is so small that no definitive conclusion is possible to draw from this behaviour. Flehmen display occurred only at one occasion. This was however only a tendency for flehmen, where the upper lip was wrinkled and drawn upwards only to a very small extent. This happened during exposure to luteal phase urine. Possibly the nose ring with the cassette could have interfered with the ability or the will to show flehmen. This might thus explain why the bulls did not show flehmen behaviour. The reaction to oestrus mucus during the first minute indicates that the bulls react to pheromone-containing substances. There were, however, no significant difference between the tested substances which indicate that the heart rate of bulls not can be used as an indicator for fast identification of pheromones in body fluids.