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Anim Reprod Sci. 2017 Dec;187:109-115. doi: 10.1016/j.anireprosci.2017.10.014. Epub 2017 Oct 27.

Impact of holding and equilibration time on post-thaw quality of shipped boar semen.

Author information

1
Institute for the Reproduction of Farm Animals Schönow e.V. (IFN), Bernauer Allee 10, D-16321 Bernau, Germany; Unit for Reproductive Medicine of Clinics/Clinic for Pigs and Small Ruminants, University of Veterinary Medicine Hannover, Hannover, Germany. Electronic address: j.schaefer@ifn-schoenow.de.
2
Unit for Reproductive Medicine of Clinics/Clinic for Pigs and Small Ruminants, University of Veterinary Medicine Hannover, Hannover, Germany.
3
Institute for the Reproduction of Farm Animals Schönow e.V. (IFN), Bernauer Allee 10, D-16321 Bernau, Germany.

Abstract

Cryopreservation of boar semen is of growing interest for breeding companies. Overnight-shipping of pre-diluted ejaculates to specialized laboratories offers a practicable method, but requires fine-tuned protocols. In this study, the impact of holding post shipping at 17°C for 2 or 24h (n=10 samples) and of equilibration in lactose-egg yolk extender without glycerol at 5°C for 2, 4, 24 or 48h (n=11 samples) before freezing was investigated. Sperm-rich fractions of ejaculates from 21 mature Pietrain boars were collected at a single boar stud. After pre-dilution (1+1, v:v) with Beltsville thawing solution, samples were sent to the laboratory. Temperature profiles during transport and initial equilibration time were recorded. Semen quality post-thaw (PT) was evaluated using CASA and flow cytometry. Holding of 2h after shipping resulted in higher sperm motility (P=0.013) and beat cross frequency (BCF; P=0.047) compared to 24h. Differences between both groups vanished with prolonged incubation at 38°C PT. Equilibration at 5°C for 4h yielded the highest motility and BCF, whereas the equilibration for 48h impaired sperm motility. Membrane integrity, mitochondrial activity and DNA fragmentation index were not affected by any protocol modification. In conclusion, processing of pre-diluted boar semen shipped overnight within 2h after arrival at the laboratory is preferred to 24h of additional holding at 17°C. Extending the equilibration period in lactose-egg yolk extender without glycerol at 5°C from 2h to 4h before freezing is recommended.

KEYWORDS:

Boar semen; Cryopreservation; Equilibration; Holding time; Shipping

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