I often hear stories of people complaining that cooled transported or frozen semen had poor motility at the time of insemination. When asked if the semen was warmed prior to analysis, the typical reply is "no, the veterinarian only had his microscope with him, not a slide warmer". Sometimes I even hear that the vet didn't have a microscope with him, but carried a semen sample back to the clinic to evaluate (we've heard of it being transported in the 'fridge on the truck, a shirt pocket or even on the dashboard of the truck!!). The semen is subsequently evaluated and found to be, shall we say "less than stellar" in it's performance, and the blame is rapidly placed on the stallion or his manager. To say that this blame is unfairly placed is perhaps an understatement...
If the sample is not to be evaluated at the breeding location - although hopefully it will be - it is important that it be maintained at a suitable temperature prior to undergoing analysis. Wherever the evaluation is to be perfomed, it is absolutely essential that the analysis be performed on semen in a warmed state in order to get a clear picture of the progressive motility. While many reproductive specialists and some general practice veterinarians do carry a microscope with them on farm calls, most don't go to the extreme of carrying an incubator or slide warmer with them for this purpose, which is understandable. What is neither understandable, nor acceptable, is the subsequent pronouncement of "poor motility" upon evaluation without warming. More often than not, this is wrong, and simply upsets the mare owner, annoys the stallion owner and frustrates all concerned.
To avoid this eventuality, and in order to be able to provide a better service, it is desirable that a few minutes be spent constructing an emergency slide warmer. This can be very simple in design and cheap to produce. Indeed with a little ingenuity there can even be a variation in designs!
One simple and easily constructed emergency slide warmer consists of a sealed Zip-Loc® freezer bag filled with warm (body-temperature) water. Having a thermometer to ensure the unit is at body temperature is nice, but not essential. As a rough guide to obtaining the correct water temperature, place the back of your hand on the bag once filled. If it feels neither hot nor cold, then it is at approximately body temperature. Any air is excluded from the bag to avoid insulating bubbles, and the surface of the apparatus wiped dry.
Another even simpler emergency slide warmer requires once again warm (body temperature) water, a desert bowl, and a piece of "cling film" such as is used in the kitchen. Fill the bowl with the warm water. Next take the cling film, place it over the bowl, and allow the film to sag in the center to come into contact with the surface of the water. Ensure that the cling film seals the bowl around the edges, and no water escapes onto the outer surface of the cling film - it should be carefully wiped dry prior to use to prevent any possible water contamination of the semen sample.
You now have a makeshift slide warmer!!
Take the microscope slide and cover slips and place them on the top of your slide warmer. Allow them to warm for 5 minutes, and then put the drop of semen to be evaluated onto the slide. Allow it to warm a further 5 minutes, place one of the warmed cover slips over the sample, and evaluate the motility under your microscope. You will be amazed at the increase in motility over the semen sample when still cool!
Note that it is also advisable to turn on the microscope light source at the same time as commencing constructing the "slide warmer", as this will warm up the microscope stage somewhat, assisting in accidental re-cooling of the sample during analysis.
These slide warmers are not accurate scientific instruments, but I bet if they were used more, there would be more "high motility" cooled semen shipments seen, and more happier mare and stallion owners!