Sperm Production of Holstein Bulls Determined from Testicular Spermatid Reserves, after Cannulation of Rete Testis or Vas Deferens, and by Daily Ejaculation

The relationship between sperm production and sperm output was reexamined with data from 50 bulls. Sperm output in semen collected daily by artificial vagina averaged 6.46 × 10⁹/day (47 bulls). The volume (ml/day), cell concentration (10⁶ml), and sperm output (10⁹/day) from a cannulated rete testis (21 measurements) averaged 41.3, 70, and 2.83 while corresponding values for cauda epididymal semen obtained via a vas deferens cannula (20) averaged .8, 5387, and 3.93. Comparisons within bulls for pairs of measurements revealed no significant difference in the number of sperm recovered from the rete testis, from the cauda epididymidis, or representing one-half of those ejaculated daily before surgery. These values were similar to estimates of sperm production calculated with a new time divisor (5.32 days) to convert testicular spermatid reserves to sperm production. Each method used can give valid estimates of daily sperm production. In normal bulls few if any sperm are resorbed in the epididymis. Sperm transport through the epididymis was not retarded by ligation of the efferent ducts. The time required for sperm to traverse the epididymis of a bull ejaculated daily averaged 8 days but ranged from 4 to 15 days.