Semen quality after thawing: correlation with fertility and fresh semen quality in dogs

Fifty-four semen samples from five dogs were evaluated both, fresh and after thawing. Some of these semen samples were mixed with autologous prostatic fluid after thawing and used to inseminate each of nine bitches 4-7 times intravaginally. All bitches conceived and the mean number (+/- SD) of conceptuses, number of corpora lutea and ratio between conceptuses and corpora lutea (implantation rate) were 5.7 +/- 2.8, 9.4 +/- 1.1 and 0.63 +/- 0.34, respectively. The mean incidence of normal sperm morphology and progressively motile spermatozoa for all semen samples were 71.5 +/- 13.5% and 74.4 +/- 7.1%, respectively, in fresh semen and 52.0 +/- 18.5% and 53.4 +/- 12.6% in frozen-thawed semen. Extension rate was 1:3 for all semen samples and the mean sperm concentration after thawing was 12.08 +/- 6.66 x 10(7) ml-1. The only semen quality variables after thawing that were correlated with implantation rate were the number of spermatozoa inseminated on day-2 and number of progressively motile spermatozoa inseminated on day-2 (where day 0 is the day of onset of dioestrus as determined by cytology) (Spearman's rank correlation coefficient > 0.7, n = 9, P < 0.05). This study suggests that it is essential that frozen-thawed semen is inseminated on day-2 and that an insemination dose of 10-11 x 10(7) progressively motile frozen-thawed spermatozoa is adequate to achieve a mean implantation rate of 75% or higher. The incidence of either proximal or distal cytoplasmic droplets in fresh semen was negatively correlated with motility after thawing in three of five dogs (Spearman's rank correlation < -0.5, n = 6-17, P < 0.05). Neither the percentage spermatozoa with normal morphology in fresh semen nor the percentage progressively motile spermatozoa in fresh semen nor the concentration of spermatozoa after thawing were correlated with motility after thawing. Fresh semen quality, with the exception of the incidence of retained cytoplasmic droplets, has little value in predicting the progressive motility after thawing in frozen dog semen.