Things You Don’t Need To Worry About When Receiving Chilled Semen!

“I couldn’t see the cells when I looked at the semen under the scope.”

When putting a cover slip onto a drop of semen on a microscope slide, you can never be sure what thickness the layer of semen will be. Because the amount of semen you are looking at is therefore never uniform. It is not possible to make subjective judgments about the overall number of sperm cells that you have been sent when receiving chilled canine semen.

A more concentrated sample is not necessarily a better one, especially when looking at a chilled semen sample. Chilled semen is often prepared by technicians who have not received adequate training. As such, the sample is often “under-extended” (has not diluted enough during processing), and will appear more concentrated. Refer to the paperwork that came with the semen shipment.

“There was sediment at the bottom of the syringe/tube – all the sperm cells must have died!”

When sperm cells are transported at 5°C, they are only metabolizing at 10–12% of their usual rate. This means that they will remain viable for long enough to be shipped. It also means that they are not “swimming” much, if at all. Since they are likely to fall towards the bottom of the syringe or tube, they settle there. It does not mean that the cells have died. There will inevitably be a certain number of cells that die during transit. However, you can check the die-off rate by making an estimate of the percentage of the sperm cells that are progressively motile under the microscope. Then compare that figure to the initial progressive motility shown on the accompanying paperwork when you were receiving chilled canine semen.

Simply invert the syringe/tube a few times before insemination to ensure that the semen dose is properly mixed.

“We were only sent a very small volume of semen – there won’t be enough to get the bitch pregnant!”

The volume is not important. What is important is that you have received at least 100 million progressive sperm cells, and preferably 150–350 million progressive sperm cells. Now, those sperm cells could be in a volume as low as 2 ml, or they could be in a volume of 50 ml. Neither is necessarily a problem. It depends on a huge number of factors including the concentration of the raw semen when collected. Additionally, the initial progressive motility and the extender that are used also play a role. But rest assured when receiving chilled canine semen that these factors are often managed.

The semen dose should be provided with paperwork describing how it has been extended. This data, together with your estimate of progressive motility on arrival, should tell you whether or not you have enough sperm cells in the dose.

“The progressive motility of the sperm cells was low on arrival (“only 25%” or similar).”

As described previously, the progressive motility is important, but only relevant in combination with the concentration and volume. You should be receiving a minimum of 100 million progressive sperm cells. But preferably 250–500 million to achieve optimal pregnancy rates.

You should carry out the following calculation to see if you have been sent enough sperm cells:
(Volume × Shipping concentration in millions per ml) × Progressive motility (as a decimal) = X

X should be at least 100, but preferably 250–500 or more. A sample with 10% progression can still be good enough to produce acceptable pregnancy rates when receiving chilled canine semen…

(40 ml × 65 million sperm per ml) × 0.1 = 260 million

(Volume × Shipping concentration in millions per ml) × Progressive motility (as a decimal)

In this example, despite the 10% progression, you still have 260 million progressive sperm cells.

The semen dose looks like it has been made with an egg yolk-based extender; does that mean my bitch will have a reaction to it when she is AI’d?”

It is a misconception that the inclusion of egg yolk in extenders is a bad thing for the bitch’s uterus. Research has shown that egg yolk in extenders actually reduces the inflammatory response of the bitch’s uterus. Egg yolk inclusion is often beneficial to the survival of sperm cells, so if anything, it is a good sign. It is not something to worry about when receiving chilled canine semen! However, if egg yolk is not included and the dose is still yellow, then you may need to worry about urine contamination or other problems!