Plant oestrogens; the cause of decreased fertility in cows. A case report.

During the stall feeding period 1982-1983, it was established that serious fertility disturbances, indicating oestrogenic stimulation, had occurred in a herd of cattle in an area supported by the College of Veterinary Medicine's ambulatory clinic. Whilst investigating the cause of these disturbances it was proven that the silage administered during this period was prepared almost entirely from pure red clover aftergrowth. The oestrogenic isoflavone content of the silage (liquid chromatograph examination) and the oestrogenic strength (bioassay) were considerably great. When feeding with the fodder was subsequently discontinued the disturbances ceased to occur and the cows became pregnant more easily. On the basis of the aforementioned incidences it was ascertained that plant oestrogens were almost certainly the cause of the fertility disturbances.