Impaired semen quality of AI bulls fed with moldy hay: a case report.

The daily quality control of semen at a Finnish artificial insemination (AI) bull station is based on subjective motility and sperm morphology of young bulls entering the semen collection program. Semen quality dropped suddenly in autumn 1998. During 5 consecutive months, the number of rejected ejaculates and discarded frozen semen batches due to poor motility increased, and the number of all forms of abnormal spermatozoa increased. However, for the accepted ejaculates, a 60 day nonretum rate was normal. The summer of 1998 in Finland was rainy, and the hay used in the AI station was visibly moldy. Immunoassay and gas chromatography-mass spectrometry (GC-MS) detected Fusarium mycotoxins HT-2 and T-2, but no zearalenone in the hay. Occurrence of mycotoxins such as T-2 and HT-2 in the moldy hay coincided with, and may have been responsible for the impaired semen quality in AI bulls. This case report will draw the attention to the possible hazards when feeding moldy hay.