Volatile fatty acids in urine and vaginal secretions of cows during reproductive cycle.

Levels of volatile fatty acids (VFA) in vaginal secretions (VS) of cows were nearly independent of concentration changes of acids in the gastrointestinal tract, while levels in urine showed marked dependence. During three-week cycles, the VFA concentrations in VS increased shortly before heat and decreased to one third on days 19-22. Some cows showed an immediate increase after heat while in others the increase was slow and gradual. Moderately increased levels at midcycle were probably related to interovulatory follicle growth. Content of VFA in VS of pregnant cows was significantly above the level of the postestrus drop. Some pregnant cows in the first two thirds of gravidity had substantially higher levels of VFA than the other cows. Changes in VFA levels have a potential value for estrus detection and pregnancy diagnosis in cows. The gas chromatographic method used is too slow and tedious for practical application, but a reliable semiquantitative test for rapid proof of VFA or acetic acid in VS would be a very useful device for field use. It would have a substantial impact on the economy of cattle production by minimizing the loss of time due to delayed breeding.