view - Department of Reproduction, Obstetrics and Herd Health

CHAPTER 1.2
of a stallion stored for 24h at either 5°C or 20°C gave an identical pregnancy outcome, however, all
motility parameters tested decreased significantly more when stored at 20°C in comparison with
storage at 5°C (Varner et al., 1989). Storage using a synthetic extender like HGLL-BSA, is preferably
done at 15°C under aerobic conditions (Magistrini et al., 1992), which was confirmed by Battelier et
al. (1997) for HGLL-NPPC. Semen preserved in HGLL-NPPC at 15°C under aerobic conditions showed a
markedly better motility compared to storage at 4°C under anaerobic conditions. In a more recent
study (Chanavat et al., 2005), semen storage at 15°C in INRA96 resulted in lower in vitro quality,
whereas fertility in vivo was the same as compared to storage at 4°C. When using EquiPro as defined
extender, no difference was present for semen stored under aerobic or anaerobic conditions, nor at
15°C nor at 5°C. The latter temperature, however, resulted in a better motility for samples stored up
to 3 or 4 days when no antibiotics were added to the extender (Price et al., 2008).
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The storage of equine semen at 15°C in INRA96 under aerobic atmosphere did not only result
in an excellent motility in vitro, it also yielded good in vivo fertility results, even after long term
storage (72h) at this temperature. In fact, it was better when compared to storage at 4°C in INRA82
(Battelier et al., 1998).
1.2.3. Transport of semen
As described above, the ideal temperature for preserving equine semen might differ
depending on the type of extender used. Semen is generally best preserved at 4-5°C in anaerobic
conditions using any extender, mainly skimmed milk extenders, except when using INRA96, storage
at 15°C in aerobic conditions is preferable. A wide variety of passive cooling devices, for cooling and
storage to 4-5°C, is available. These devices have variable cooling rates since the cooling process
slows down as the internal temperature is reduced (Brinsko et al., 2000b). The Equitainer I and II
are the best known passive cooling devices for gradual slow cooling and transport of equine semen.
A first version of the Equitainer, made by Douglas-Hamilton et al. (1984), was highly successful in
obtaining a slow cooling curve leading to a plateau at a constant temperature of 5°C. Furthermore,
the Equitainer is extremely durable and designed for reuse. However, the initial cost of the shipping
container and the inevitable charges for return shipping, are the major disadvantages of this device.
Other systems, which are disposable and cheaper, are available as well (Fig. 11). All of these systems
fail under extreme temperatures in keeping the samples at 4-5°C, however, most of them provide an
adequate protection when the container is kept at 22°C. A higher ambient temperature might
influence the core temperature of the sample, nevertheless, in vitro semen characteristics are not
affected in most systems. Lower temperatures might be more cumbersome, especially if they are