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Pheromones for modulating reproduction in cattle

Declining dairy cow fertility, largely attributable to increasing milk yields, is of major 
concern to dairy farmers worldwide. New tools for reproductive management, to 
replace exogenous hormones, would be of great interest. Chemical communication in 
cattle has been suggested to cause modifications of the oestrous cycle. Here, 
reproductive parameters were monitored in ten dairy heifers during five oestrous 
cycles. They were exposed to distilled water (control) or oestrous urine and vaginal 
mucus (treatment). Four of them were also subjected to intensive blood sampling to 
study the treatment effect on the LH pulsatility pattern (LHP) preceding the 
preovulatory LH surge (LHS).We found that the treatment had significant effects on 
when the different signs of oestrus occurred and on the intensity of oestrus expression. 
There was a tendency for treatment to have an effect on LHS characteristics whereas 
LHP was significantly affected by the treatment. To find a quick bioassay to detect 
bioactive bovine body fluids, two heifers and two bulls were exposed to different body 
fluids while their heart rates were registered. Although the exposure caused significant 
effects, they were not of sufficient magnitude to be useful. Further attempts to find a 
bioassay to identify oestrus-specific compounds included using the face fly as a 
biological detector. Female flies were allowed to choose between either oestrous (OU) 
or luteal urine (LU) and distilled water (control) in a Y-tube olfactometer. Flies were 
significantly repelled by OU, but not by LU. Gas chromatography coupled with 
electroantennographic detection (GC-EAD) revealed no behaviourally active, oestrusspecific 
compounds. Comparison of chromatograms, however, showed that cetyl 
alcohol was more abundant in OU than in LU. When tested at different doses, the 
lowest dose of cetyl alcohol was found to attract flies, while the second lowest dose 
was repellent. 
 
We found effects of exposure to body fluids on cyclicity in heifers, as well as on 
heart rate in cattle, which supports the existence of bovine pheromones. We also found 
that the face fly could discriminate between OU and LU, probably based on the amount 
of cetyl alcohol in the samples. Neither monitoring of heart rate, nor using the face fly 
as a biological detector, were suitable bioassays for detection of bovine pheromones.