Fertility of frozen-thawed dog sperm with the addition of homologous prostatic fluid or protein-free sperm TALP prior to intravaginal insemination of bitches

Abstract

The addition of prostatic fluid to intravaginally inseminated frozen-thawed semen resulted in an increase in pregnancy rate in bitches when compared with frozen-thawed semen inseminated on its own (Nöthling and Volkmann, 1993). However, the volume and viscosity of the inseminates varied greatly, which may have caused the improvement in fertility. Sperm TALP is a sperm-friendly fluid used extensively inin vitro processes. It was modified to exclude albumin to avoid any potentially beneficial effect. Twenty-eight young, healthy German shepherd bitches were inseminated with frozen-thawed semen to which either prostatic fluid (Group P) or albumin-free TALP (Group T) was added to provide an insemination volume of 7 ml. All bitches were inseminated daily from the onset of the appearance of shrunken angular folds on vaginoscopic evaluation until the day prior to diestrus as confirmed by cytological evaluation. Approximately 50 million progressively motile sperm was used per insemination. The semen was inseminated intravaginally after the addition of the appropriate fluid. Bitches were spayed 3 weeks after the onset of dioestrus and the number of conceptuses and corpora lutea counted. The non-resorbed conceptuses were taken as the litter size. The number of corpora lutea did not differ between the groups (n=25, P=0.496). The pregnancy rate between the groups did not differ. Among pregnant bitches, Group P (n=13) had significantly higher litter sizes than Group T (n=12) (P = 0.036). For the 13 bitches that received prostatic fluid, there were 139 corpora lutea and 80 conceptuses whereas, for the 12 bitches that received albumin-free TALP, there were 117 corpora lutea and 44 conceptuses (Chi-squared, P=0.002). Prostatic fluid has a positive influence on the fertility of frozen-thawed sperm more than by merely increasing the volume or decreasing the viscosity of the inseminate. The exact mechanism of its influence remains unknown.