Secular sperm trends in stallions between 1981 and 1996

Several reports have suggested that human semen quality has declined throug hout the world over the last few decades. Chemicals in the environment acti ng as endocrine disrupters have been implicated as a possible cause. If thi s is indeed the case, then similar effects may be observed in animals. We a nalyzed 1489 ejaculates collected from 390 Breton draught stallions between 1981 and 1996. Semen was collected from all the stallions at a single cent er, according to standardized semen collection protocols and laboratory met hods. Semen volume decreased slightly but significantly and there was an in crease in sperm concentration over the study period. However, total sperm p roduction was unchanged. Seminal fluid volume is controlled by accessory se x glands, which are regulated by androgens. Chemicals with antiandrogenic p roperties have been detected in the environment. By affecting the developme nt or function of accessory sex glands, these chemicals may be at least par tly responsible for the observed decrease in semen volume.