BLOOD-ACETALDEHYDE FLUCTUATES MARKEDLY DURING BOVINE ESTROUS-CYCLE

Our interest in the study of volatile sexual pheromones given off by c ows as they enter estrus caused us to use blood head-space gas chromat ography (HSCG) to monitor changes of volatile compounds during 18 comp lete estrous cycles of five adult cows. We observed several distinct c omponents in the chromatographic profile, but only one component chang ed in concentration with the stage of the estrous cycle. Analysis of 1 64 blood samples revealed that the size of the peak representing this compound varied widely during the cycle and among cows. However, all c ows typically showed a similar qualitative pattern of a rise and then a fall in peak area just prior to or at the time of standing estrus (t he day when cows will stand still for mounting). This peak of interest eluted from the chromatographic column in less than 3 min at room tem perature. Thus, we knew that the molecule was small and highly volatil e. This was confirmed by preliminary mass spectral analysis, which sug gested some candidate compounds. Spiking of blood samples with small a mounts of these candidate compounds revealed that acetaldehyde co-elut ed with our peak of interest. To collect sufficient quantity of this c ompound for mass spectral identification, we tested various ways to in crease head space concentration. Best results occurred by adding potas sium carbonate to the blood and heating it for 30 min at 90-degrees-C. This head-space gas was then derivatized by bubbling it through an ac idified solution of 2,4-dinitrophenylhydrazine. Mass spectral analysis of the derivatized product confirmed that our compound of interest wa s acetaldehyde. We suggest that sexual hormones regulate the metabolic production of acetaldehyde. Estrus and ovulation could potentially be predicted by non-invasive monitoring levels of acetaldehyde in body f luids such as saliva, milk, sweat or even breath.