Tail Stump effect on Hereford bulls

case report

Abstract

This paper reports the first case known in Uruguay of bulls with a middle piece sperm defect recognized as ·tail stump". Two related sexually mature Hereford bulls were tested for use in natural breeding. The sperm morphology studied by means of a differencial interference contrast microscope (1000X) revealed a high frequency of middle piece defects described as tail stump (bull A: 88,5%; bull B: 18,5%). The histopathological studies of bull A showed evidence of mild testicular hypoplasia and a low rate of spermiogenesis, corresponding with a very poor sperm concentration and sperm molility, consequently this bull had a sterilizing oligoteratozoospermia. On the other hand, bull B presented a normal sperm concentration with a very good motility and it seems to be a fertile bull in spite of the abnormal sperm cells found. The hypotesis of being an hereditary defect in spermiogenesis inherited by a single recessive gene is enhaced, therefore it is emphasized the importante of performing spermiogram studies in bulls where suspected carriers could be detected and removed from service.