view - Department of Reproduction, Obstetrics and Herd Health
view - Department of Reproduction, Obstetrics and Herd Health
view - Department of Reproduction, Obstetrics and Herd Health
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
CHAPTER 4.1<br />
4.1.2. Introduction<br />
140<br />
Numerous studies have demonstrated the beneficial effect <strong>of</strong> diluting raw semen with an<br />
appropriate extender. As such, the negative influence <strong>of</strong> seminal plasma (SP) on the preservation <strong>of</strong><br />
equine sperm can be reduced. Centrifugation <strong>of</strong> diluted equine semen <strong>and</strong> subsequent resuspension<br />
<strong>of</strong> the sperm pellet in fresh extender can even further reduce the amount <strong>of</strong> SP in stored samples. A<br />
small proportion <strong>of</strong> SP in semen improves sperm motility after cooling <strong>and</strong> storage (Jasko et al.,<br />
1991).<br />
However, centrifugation itself may act like a double edged sword exerting both beneficial<br />
<strong>and</strong> deleterious effects on sperm motility (Martin et al., 1979). Although the number <strong>of</strong> sperm cells<br />
can be maximized by increasing centrifugation time <strong>and</strong> force, physical damage is exerted on the<br />
sperm cells at the same time. The direct negative outcome <strong>of</strong> centrifugation on semen quality is<br />
demonstrated by the decrease in motility <strong>and</strong> velocity in contrast to uncentrifuged controls (Jasko et<br />
al., 1991) which indicates that the centrifugation protocol (CP) may play an important role in the<br />
quality <strong>of</strong> the inseminate. After 24h <strong>of</strong> cooled storage the harmful effect <strong>of</strong> centrifugation is no<br />
longer present (Jasko et al., 1991).<br />
A CP <strong>of</strong> 600 × g for 10 min is commonly used for equine semen (Ecot et al., 2005; Knop et al.,<br />
2005; Vidament et al., 2000; Weiss et al., 2004). In literature, data on the amount <strong>of</strong> sperm loss after<br />
using this protocol are contradictory <strong>and</strong> vary from 1.9% (Weiss et al., 2004) to 25% (Ecot et al., 2005;<br />
Knop et al., 2005). Nowadays, it is generally accepted that sperm losses will vary around 25% when<br />
diluted semen is centrifuged at 400-600 × g for 10-15 min (Aurich, 2008; Loomis, 2006).<br />
The importance <strong>of</strong> an appropriate CP has been clearly demonstrated for human sperm. The<br />
duration <strong>of</strong> centrifugation was shown to be more important than the centrifugation force for causing<br />
iatrogenic sperm membrane injuries which resulted in an increased formation <strong>of</strong> reactive oxygen<br />
species (Shekarriz et al., 1995). In boars, similar findings were described: a CP with a high g-force for<br />
a short time (2400 × g for 3 min) was used without detrimental effects on sperm yield compared to<br />
the st<strong>and</strong>ard regime (800 × g for 10 min) (Carvajal et al., 2004). Additionally, a positive effect on<br />
semen quality after cryopreservation was detected when using high g-forces for a shorter period <strong>of</strong><br />
time (Carvajal et al., 2004). Experiments with equine semen have been performed where semen was<br />
centrifuged at 400 × g for an increasing period <strong>of</strong> time. Sperm loss was approximately 20%, if<br />
samples were centrifuged for 10 min or longer, while no adverse effects on motility immediately<br />
after centrifugation were present, unless semen was centrifuged for 20 min. However, effects on<br />
preserved by cooling or freezing were not determined (Heitl<strong>and</strong> et al., 1996). A high g-force for a