ULTRASONOGRAPHIC MEASUREMENT OF STALLION ACCESSORY SEX GLANDS AND EXCURRENT DUCTS DURING SEMINAL EMISSION AND EJACULATION

Accessory sex gland and excurrent duct activity of 10 stallions was vi sualized with transrectal ultrasonography during seminal emission and ejaculation. First and last penile urethral contractions were defined as the start (0 sec) and end of ejaculation, respectively. Duration of ejaculation (n = 63 ejaculations) averaged 6.15 +/- 2.98 sec. Penile urethral contractions occurred an average of 6.2 +/- 2.2 times per eja culation. Right bulbourethral glands (n = 19 ejaculations) alternated repeatedly from ovoid to flattened, irregular shapes during ejaculatio n. Cross-sectional area of right bulbourethral glands did not change ( p > 0.40) between 3 sec before ejaculation and the end of ejaculation. Cross-sectional area of right prostatic lobes (n = 17 ejaculations) d ecreased (p < 0.01) between 3 sec before ejaculation and the end of ej aculation, with decreases (p < 0.05) at 2, 1, and 0 sec before ejacula tion and at the time of the second penile urethral contraction. Excurr ent ducts of ampullae (n = 17 ejaculations) first appeared to dilate w ith fluid at 2.60 +/- 0.23 sec before ejaculation and subsequently dil ated an average of 3.4 +/- 0.3 times between 3 sec before ejaculation and the end of ejaculation. Fifty-three of 58 (93% ) ampullar duct dil ations occurred prior to the start of ejaculation. During each dilatio n of ampullar ducts, fluid remained visible for 0.23 +/- 0.04 sec. Flu id was detected within the lumina of vesicular gland excurrent ducts d uring the 6 of 17 monitored ejaculations that produced detectable gel. First and last dilations of vesicular gland ducts began at 1.31 +/- 0 .58 and 5.12 +/- 0.96 sec, respectively, and a total of 4.3 +/- 0.7 di lations occurred between 3 sec before ejaculation and the end of ejacu lation. During each dilation of vesicular gland ducts, fluid remained visible for 0.73 +/- 0.21 sec.