Effects of Estradiol Benzoate Injections on the Characteristics of Bovine Semen

Estradiol benzoate was injected into two normal bulls at levels ranging ~rom 0.99 to 70 rag. per week. At levels up to and including 15 mgi per week, supplementary estrogen produced statistically insignificant increases in motility, per cent live spermatozoa, volume per ejaculate, spermatozoa concentration, and total spermatozoa per ejaculate. The per cent of abnormal spermatozoa was decreased but the decrease was not statistically significant. Levels of 35 and 70 rag. per week decreased semen quality. Seventy milligrams per week decreased the libido in one bull but had no effect on the libido of the other.