Research: New way of examining boar extender efficacy
Joint German and English research has paved the way for a new method of determining the efficacy of certain extenders when storing and chilling boar semen.
The researchers, attached to the University of Veterinary Medicine in Hanover, Germany and the University of Cambridge, UK, zoomed in on the concept of ‘capacitation’ for their research. This is a phase of maturation of spermatozoa – usually happening after ejaculation. When using artificial insemination, in vitro, capacitation can occur by incubation.
In the trial, semen was diluted in two different extenders:
* Beltsville Thawing Solution (BTS); and
* Androstar Plus (Minitube).
The researchers report: “They were kept for three hours at 22°C or stored at 17°C, 10°C and 5°C. Semen was analysed at 24 and 96 hours of storage. Motility and membrane integrity remained at high levels, except for lower values when stored in BTS at 5°C.
“Washed sub-samples were incubated in capacitating medium (Tyrode) and control medium and assessed for intracellular calcium concentration and integrity of plasma membranes using a flow cytometer. Based on the loss of low-calcium live cells in a kinetic approach, the specific response to capacitation stimuli was determined.
“There was a higher loss of response in semen stored hypothermically in the standard extender BTS compared to Androstar Plus. Assessment of extent of phopholipid disorder under capacitating and control conditions by use of the merocyanine staining did not reveal any significant extender-related differences.
“A field insemination trial with 778 sows was performed to relate in vitro results to fertility. Fertility parameters did not differ in semen stored up to 48 hours at 10°C in Androstar Plus compared to controls stored at 17°C in BTS.”
In short, the researchers conclude that “ assessment of specific reactivity to capacitating stimuli appears to be a sensitive tool for detection of extender-dependent alterations in functionality of chilled boar spermatozoa.”
The research is relevant as spermatozoa, especially those of the porcine species, are highly susceptible to in vitro-chilling and -ageing. Extenders are continuously developed to protect boar spermatozoa from chilling injury. New semen extenders and other modified preservation strategies require sensitive testing for essential sperm functions.
The study was published online, ahead of printing, in the Journal of Animal Science, August 2013.
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