Compartmental Analysis of Sources of the Bovine Ejaculate

Abstract

A compartmental analysis mcdei applicable to many experimental situations was used to estimate the volume contributed to ejaculated bull semen by the (1) seminal vesicles, (2) epididymides and (3) other sources. The fluid which drips from the urethra during sexual preparation was assumed to be characteristic of the latter compartment. Fructose, sperm, and chloride (Cl), respectively, were used as markers. Estimates of vesicular fluid fructose concentration ranged from 959 to 1658 mg/bC ml; similarly, estimates of epididymal sperm concentration ranged from 3.35 to 7.10 X 109 sperm/mi. Average urethral fluid Cl concentrations ranged from 487 to 517 mg/lOO ml. The uniformity in Cl among bulls supports the postulate that urethral fluid essentially is a filtrate from a rather uniform pool, the blood. For first ejaculates it was estimated that each of the three areas contributed approximately 1.5 ml to the average ejaculate of 17to 22-month-old bulls and similarly each contributed about 2.0 ml for 3-year-old bulls. For both groups of bulls, epididymal volume contribution to second ejaculates was only about half that of first ejaculates, but volume contributions from the other two compartments were similar to