Effects of season, nutrition and hormone treatment on the fructose content of ram semen

Abstract

A marked seasonal fluctuation was found over 2 years in the concentration of seminal fructose, and in the total amount per ejaculate, in Merino and Romney Marsh rams at pasture. Values were high in autumn, low in spring. No such fluctuation was observed in rams kept on a constant diet under a natural or a reversed annual light cycle; but when the energy intake of the rams was decreased by 30%, there was a sharp decline in the amount of fructose per ejaculate.

In castrated rams the amount of fructose per ejaculate was linearly related to log (dose of injected testosterone). In entire rams injections of human chorionic gonadotrophin caused an increase in seminal fructose, but thyroxine injections were without effect. Stilboestrol injected at levels of 25 and 250 µg/day caused marked decreases in seminal fructose. Increasing the frequency of electro-ejaculation from once per 2 weeks to twice weekly caused an increase in seminal fructose.