Pre-freezing incubation of intratesticular semen of rainbow trout (Oncorhynchus mykiss) XX-males
Female rainbow trout reaches marketable size before male. Females are sex-reversed to produce XX-males, which mostly lack of sperm ducts. XX-males are sacrificed to obtain intratesticular sperm. Semen cryopreservation maximizes the use of a single male but post-thaw motility is often low. The aim of this study was to test a pre-freezing incubation of intratesticular semen in seminal plasma as a mean to improve post-thaw sperm motility. Intratesticular semen was diluted in seminal plasma obtained from normal XY-males at three ratios (semen:plasma): 1:0 (undiluted), 1:6 and 1:8. Half of the semen volume was immediately frozen in a medium containing glucose, egg yolk and DMSO . The other half was first incubated for 1:30 h at 4ºC and then frozen. Post-thaw sperm motility of undiluted semen (1:0) submitted or not to the pre-freezing incubation period was very low (0-6%). Post-thaw sperm motility of semen diluted 1:6 and 1:8 in seminal plasma increased from 16-18% to 50-60% when submitted first to the pre-freezing incubation period and then frozen. Incubation of intratesticular semen in seminal plasma prior to freezing, increased post-thaw motility.