Fertility of Bovine Spermatozoa from Rete Testis, Cauda Epididymidis, and Ejaculated Semen

A total of 141 heifers and cows, predominantly Holsteins, was used to compare fertility of sperm entering and leaving the epididymis. Testicular and cauda epididymal sperm were obtained through indwelling cannulae while ejaculated sperm were collected before surgery on seven Holstein bulls. After deposition of 200 × 10⁶ sperm in the uterine body, 106 females were killed on day 4 of a natural estrous cycle. Percentages of fertilized ova were 0% for testicular sperm, 84% for cauda epididymal sperm, and 94% for ejaculated sperm. Fertilizing capacity of cauda epididymal and ejaculated sperm was not significantly different. In contrast to observations for the other sperm types, testicular sperm were not detected on ova recovered on day 4. Testicular sperm also were not associated with five other ova, or in oviduct flushings, recovered 12 to 14 h after uterine body inseminations. However, epididymal or ejaculated sperm were plentiful in ova and flushings from two cows killed 13 to 14 h after insemination. The infertility of testicular sperm may result from intrinsic factors, a failure of sperm transport into the oviducts, or unusually rapid elimination of testicular sperm from the oviducts. Attempts to inseminate sperm surgically into the oviduct of 26 cows were unsatisfactory. Placement of sperm within the oviduct was uncertain with one technique while abnormal ovulation and/or corpus luteum formation, accompanied by a low incidence of ovum recovery, followed surgical inseminations by laparotomy.