The literature contains a bewildering number of reports on conception rates obtained in various artificial insemination (AI) programmes, but some of the confusion is caused by environmental differences and some by differences in methods of assessing fertility.
P. Shannon and B. Curson
Summary. Most (94%) of the aromatic l-amino acid oxidase activity in dead bovine spermatozoa was recovered in tail preparations. The enzyme was released from the cell in sodium citrate but not in sodium phosphate or sodium chloride solutions but oxidase activity was not significantly different in sodium phosphate or sodium citrate buffers (9·6 μl O2/h and 11·2 μl O2/h). The activity in ejaculated spermatozoa was correlated with the percentage of dead spermatozoa (r = 0·954, P < 0·01) but could not be detected in freshly collected epididymal spermatozoa. Killed epididymal spermatozoa showed oxidase activity (10·1 μl O2/h) similar to that of killed ejaculated spermatozoa (9·2 μl O2/h).
It is concluded that death of spermatozoa occurs in the ampulla and/or at ejaculation and that between-bull differences in the percentage of dead spermatozoa are a consequence of differences between bulls in conditions in the ampulla and/or at ejaculation.
P. Shannon and B. Curson
Summary. At limiting velocity 50 × 106 dead spermatozoa consumed 13·6 μl O2/h and degraded 6·1 × 10−7 mol l-phenylalanine/h. Substrate concentration in egg yolk was equivalent to 6·1 × 10−3 m-l-phenylalanine. At a substrate concentration of 3 × 10−2 m-l-phenylalanine, oxidase activity was significantly affected by oxygen tension (r = 0·947, P < 0·01) and temperature (r = 0·995, P < 0·01). Non-return rates were not affected when semen was stored at 5°C in 20% egg yolk diluents with catalase but were significantly increased with semen stored at ambient temperatures of 15–23°C.
Joan W. Baas, P. C. Molan, and P. Shannon
Summary. When ejaculated bovine semen was washed twice with Ficoll the spermatozoa, resuspended in buffer, became immotile. Motility could be restored by addition of seminal plasma from vasectomized bulls and by addition of both bovine serum albumin (BSA) and theophylline. Motility could be restored and maintained at 37°C to a variable extent with BSA alone. When this motility ceased it could be revived with theophylline or seminal plasma. When spermatozoa, inactivated by washing with Ficoll, were reactivated with seminal plasma the time that motility lasted at 37°C before it was irreversibly lost depended on the concentration of seminal plasma: the more seminal plasma added, the shorter the duration of motility. This suggested that seminal plasma contained separate factors which restored motility and led to permanent inactivation of the spermatozoa. A motility-stimulating factor was present in the low molecular weight fraction of seminal plasma which had been passed through an ultrafilter of retention Mr 500 and the damaging effect was confined to the high molecular weight non-dialysable fraction.