Effect of seminal plasma on the in vitro fertilizability of bull spermatozoa

The aim of this study was to determine the effect of seminal plasma on the in vitro fertilizability of bull spermatozoa and developmental capacity of cultured oocytes. For the in vitro fertilization (IVF) frozen-thawed cauda-epididymal spermatozoa (EPI) and ejaculated spermatozoa deprived of seminal plasma immediately after collection (SDS) and control (ES) were used. EPI spermatozoa were recovered from bulls randomly selected at the slaughterhouse, whereas ejaculated spermatozoa were collected from selected bulls showing the low (two animals) and the middle (two animals) in vitro fertility (blastocysts yield ⩽ 10% and 11–20% of inseminated oocytes, respectively). vitro embryo production efficiency with frozen-thawed EPI spermatozoa was high and approached a similar level for individual bulls (83.7 ± 10.3, 80.2 ± 11.8 and 30.6 ± 5.0%, mean ± SD, fertilization, cleavage rate and blastocysts yield, respectively). The comparison of the fertilizability of SDS and ES sperm showed that significantly more (P < 0.001) oocytes were fertilized, cleaved and developed to the blastocyst stage when the in vitro insemination was done with SDS sperm than those inseminated with ES sperm (63.3 ± 18.2, 52.0 ± 19.2 and 16.2 ± 9.4% versus 50.1 ± 20.1, 39.9 ± 24.8 and 10.6 ± 9.5%, mean ± SD, respectively). The absence of seminal plasma during capacitation has appeared especially favorable to embryo production efficiency of the low in vitro fertility bulls. clusion, these data provide evidence that for IVF purposes the use of frozen EPI spermatozoa can be recommended in the case of mass embryo production of unknown genetic value while removal of seminal plasma from bull ejaculate immediately after collection can be recommended as a routine procedure for semen freezing to improve the in vitro fertilizability.