Riboflavin in Yellow Semen

Abstract

MOST specimens of bull semen are almost white, but during the course of unrelated studies¹ on spermatozoa it was observed that the semen from one particular bull was quite yellow. The colour was confined to the plasma fraction and ultra-violet light produced a green fluorescence similar to that emitted by riboflavin. Other reports^2–4 have since been noted which suggest that the yellow pigmentation of bull semen may be attributed to riboflavin, and recently eight bulls producing yellow semen have been located, thus permitting a more critical and extensive investigation. The production of yellow semen was characteristic of these bulls, which were located in scattered parts of Australia and New Zealand. All bulls producing yellow semen were of the Friesian breed, and six were the first, second or third generation descendants of one sire. The pigmentation apparently does not affect the fertility of the semen since the bulls were in use at artificial insemination centres and the spermatozoal concentration and morphology were normal.