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Aging Phenomena in Spermatozoa. I. Fertility and Prenatal Losses with Use of Liquid Semen

Department of Dairy Science and the Statistical Service Unit, University of Illinois, Urbana

ABSTRACT

Data on the artificial insemination of 423,054 cows were sorted by age of the spermatozoa when insemination occurred. Two studies, completely orthogonal in design, were made of the effects of spermatozoan aging on their capacity to fertilize ova and to sustain normal physiological development and ontological sequence in embryo growth. The semen was aged at 4–5 C in a yolk-citrate-milk diluent for five days after collection, the date of collection being Day 1. The evidence obtained indicates that from Day 1 to Day 2 the fertility increased and the incidence of prenatal losses decreased, but that after Day 2 there was a consistent decrease in fertilizing capacity of the spermatozoa and an associated increase in prenatal death of those developing zygotes which were formed. Theories to explain each of these phenomena are based on the view that normal spermatogenesis involves the production of at least a minimum number of spermatozoa containing defective chromatin which, nevertheless, compete well early in their independent life for fertilization sites in fertilizable eggs. However, these spermatozoa with defective chromatin can sustain that early fertilization rate for only a short time, after which the preponderance of fertilization is by spermatozoa with adequate chromatin. As such normal spermatozoa age, they too gradually lose the capacity to fertilize ova; but they lose at an even faster rate the functional integrity of the genetic information chain necessary to carry embryogenesis to normal parturition.

¹ Present address: Office of the Superintendent of Public Instruction, Olympia, Washington.