title: Effect of cooling rates on post-thaw sperm motility, membrane integrity, capacitation status and fertility of dairy bull semen used for artificial insemination in Sweden.
abstract: We studied the effects of 2 different cooling rates during equilibration of semen from room temperature to 4 degrees C, at 4.2 degrees C/min (control split sample) or at 0.1 degree C/min (treatment split sample) on in vitro sperm viability post thawing and fertility after AI. Forty batches of split-frozen semen from 14 dairy bulls (Swedish Red and White breed) aged 14 to 16 m.o. or 66 to 79 m.o. were evaluated post-thawing for sperm motility (visual and computer-assisted sperm analysis [CASA], membrane integrity (fluorescent microscopy and flow cytometry post-loading with the combined fluorophores Calcein AM/EthD-1 and SYBR-14/PI); acrosomal status (with Pisum sativum agglutinin [PSA] staining); and capacitation status (CTC-assay). Fertility values (56-d nonreturn rate) of the slow cooling batches (treatment) were 0.4% units higher than for faster cooled (control) batches, but the difference was not statistically significant. Fertility values for the older bulls were 1.6% units higher than for the group of younger sires. No statistically significant correlations were found between semen viability parameters assessed in vitro and 56-d nonreturn rate. Visually assessed sperm motility, membrane integrity, capacitation and acrosomal status post-thawing did not differ significantly between cooling procedures, however the percentage of motile spermatozoa and the kinetic characteristics of spermatozoa--average path velocity (VAP), straight path velocity (VSL) and curvilinear velocity (VCL)--assessed by CASA differed significantly between cooling procedures. The results indicate that most of the in vitro sperm viability parameters post-thawing and the fertility results for bulls after AI did not differ significantly between the 2 semen cooling procedures tested.
authors.affiliation: Department of Obstetrics and Gynaecology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Januskauskas
authors.forename: J
authors.initials: J
authors.lastname: Gil
authors.forename: L
authors.initials: L
authors.lastname: Söderquist
authors.forename: M G
authors.initials: MG
authors.lastname: Håård
authors.forename: M C
authors.initials: MC
authors.lastname: Håård
authors.forename: A
authors.initials: A
authors.lastname: Johannisson
authors.forename: H
authors.initials: H
authors.lastname: Rodriguez-Martinez
mesh_terms: D020101:Acrosome Reaction; D000367:Age Factors; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000648:ultrastructure; D002470:Cell Survival; D015925:Cryopreservation / Q000379:methods / Q000662:veterinary*; D005260:Female; D005298:Fertility; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary; D008297:Male; D011247:Pregnancy; D012662:Semen Preservation / Q000379:methods / Q000662:veterinary*; D013075:Sperm Capacitation; D013081:Sperm Motility; D013094:Spermatozoa / Q000166:cytology / Q000502:physiology; D013548:Sweden