Epididymal sperm maturation in the ram : motility, fertilizing ability and embryonic survival after uterine artificial insemination in the ewe

Ram spermatozoa from the distal caput, corpus, and cauda epididymis and ejaculated spermatozoa were artificially inseminated in 170 ewes which had been treated with an ovulatory dose of PMSG 61 ! 4 hrs previously. Results were expressed as the percent of ewes pregnant 18 days after insemination (F = with positive progesterone assay/ Q inseminated) and embryonic survival (ES = ewes lambing/ pregnant on day 18). F =0, 8, 12, 54, 78, 80 and 72 p. 100 respectively after insemination with 20 x 10 6 total spermatozoa/horn from the caput, corpus, I, II and III, proximal cauda, distal cauda, and ejaculate. Development of sperm fertilizing ability parallelled the development of sperm motility. However when ewes were inseminated with high number of motile spermatozoa, ES was 0, 77, 86, 100 and 86 p. 100 with spermatozoa from the corpus I --!II, the corpus III, the proximal cauda, the distal cauda, and the ejaculate respectively. Thus, the sperm from middle corpus are totally unable to produce viable lambs.