The procedure is performed via small incisions in the scrotum, a few minutes of manipulation of the spermatic cords, and the closing of the wounds on the scrotum. The oxygen starved testes slowly shrivel into benign fibrous masses, and the gelding’s blood testosterone levels fall to that of a gelding castrated using standard techniques within 2 months.

Dr Saifzadeh, leader of the research group said “The new technique reduces the risk of postoperative bleeding and severe swelling at the incision sites or in the prepuce, which are common complications of standard castrations. Risks of parasite and bacterial infections are also reduced in the SLR technique”.

SLR operations would have to be carefully documented in the animal’s passport for the purpose of differentiating between SLR geldings and stallions.

Always assess semen on collection, check concentration & progressive motility and aim to inseminate 500 million progressively motile cells.

Haemacytometers bought from eBay… They normally come from China/Hong Kong, have a lengthy description about the great quality… and generally are priced at between £15-£35. “What a great deal!” I hear you cry, as you head off to eBay to get yours. DON’T!

The quality of these haemacytometers is not adequate for accurate estimation of sperm concentration. Those who have bought them from eBay or similar sites will tell you that the clarity of the engraving is poor, and the chambers are generally not very clear, making it very difficult to count sperm cells.

Look for an IMPROVED NEUBAUER haemacytometer. There are great quality sets available from within the UK from as little as £35.00! Look around, and get a quality chamber… You get what you pay for!

To help those of you collecting and sending out semen, we’ve produced some 4-step crib sheets with handy reminders for collecting, processing, and shipping semen.

More information to follow.

A quick flick through February or March’s horse magazines will show you how statistics are used to bolster arguments. Quite often the statistics are useful, and meaningful. However, looking at the stallion and stud adverts in Horse Deals, and Horse and Hound, I am struck by two things:

1) Not a single stallion advert (as far as I can see) shows reliable/meaningful fertility statistics.

2)Those adverts that do have a “statistic” (if we can call it that), have used a misleading and essentially meaningless number to “bolster” their advert.

For fertility statistics to be meaningful, we need to know how many mares the stallion was bred to, and how many attempts/cycles it took for those mares to become pregnant. Now, these figures are most usefully represented by showing the number of mares (as a perecentage) who became pregnant on the first cycle, or as the average number of cycles it took each mare to become pregnant. Here are some -rough- averages to see what you might expect:

Type of breeding   /    Average first cycle pregnancy rate  /   Average number of cycles for pregnancy

Natural cover or Fresh AI   / 70%   /   1.6 cycles

Chilled semen /  60%  /   2 cycles

Frozen semen  / 40%  /    3 cycles

These are rough averages, and what you might expect of each type of breeding.

I would imagine that if you’ve seen fertility statistics you’ve seen figures like (and I’m quoting these from Horse Deals) “100% in foal success rate” or “99% conception rate” or “high conception rate”. These statistics are not worth the paper they are printed on. Why do I say this? Because these numbers give you no idea of how many mares have been bred to that particular stallion/at that AI centre, and you have no idea how many cycles it took for those mares to become pregnant.

For example… Say the pretend stallion “Mr Dudd” covers 1 mare in 2008 via natural cover. She gets pregnant on the 5th cycle. What figure does the stallion owner quote? “Oh, well 100% of Mr Dudd’s mares went in foal last year” or “Mr Dudd has a 100% conception rate”. If they quoted the statistics properly, it would be an average 1st cycle conception rate of 0 (ZERO) and an average of 5 cycles for the mare to become pregnant. Now obviously, the stallion owner won’t want to quote that (and the number of mares makes the statistic almost totally meaningless (although you would question why it took 5 cycles, right?)), but quoting the “100% conception rate” figure is VERY misleading. The owner could quote:

“100% of mares pregnant within 5 cycles. Of those, each pregnancy required an average of 5 cycles. The overall percentage of cycles resulting in pregnancies was 20%”.

Let’s go for another example… Mr Dudd’s hypothetical sire, “Fye Ring Blanks” is actually quite popular, and covered 20 mares in 2008. 5 mares became pregnant on the first cycle, 5 mares on the 2nd, 5 mares on the 3rd, 2 on the 4th and 3 mares didn’t get in foal at all. Now, old Fye’s owner likes to give the impression that he’s still pretty fertile… so she looks at the numbers. 17/20 in foal… that’s 85% overall. So again, she quotes “85% fertility” which still sounds pretty good. Right? Wrong. His first cycle pregnancy rate is (5/20) 25% which is pretty low.  On average it takes 2.24 cycles to get a mare pregnant, which isn’t so bad. (Don’t forget, all these figures are totally hypothetical, so you’re unlikely to see that combination of numbers). It would be fair for the owner to quote the 2.24 cycles average, but not “85% fertility” because that leads mare owners to believe that they have an 85% chance of their mare being in foal after the first cycle, which is simply not the case. This owner could quote:

“85% of mares pregnant within 4 cycles. Of those, each pregnancy required an average of 2.24 cycles. The overall percentage of cycles resulting in pregnancies was 34%”.

So… the next time you see “100% conception rate”, “99% fertility”, or “all mares in foal in 2008″, have a think about what these statistics are actually saying. Ask the stallion owner or stud what a stallion’s fertility figures were “per cycle” last season. If they can’t give you an answer, they either don’t keep good enough records, don’t understand fertility statistics, or they know the rates are low and don’t want to tell you. Any of these reasons should be cause for concern!

Statistics can be very misleading!

So, you have a couple of attempted cycles of AI… and it looks like you’re one of the unlucky ones. Your mare isn’t pregnant. You’re talking to the vet/AI technician/stud staff and they say:

“I think she’s having a reaction to the extender”

or

“The semen has been extended with an egg yolk extender and she’s having a reaction”

Well, it sounds kind of plausible initially, but actually some very nice research from last year suggests that this really isn’t the case. Palm et al (2008) infused phosphate buffered saline,  seminal plasma, milk-based extender, and egg-yolk based extenders into the uteruses of 8 mares over four cycles, changing what was infused on each cycle, in alternating order. They then used lavage and biopsy to look at the immune response to each different infusion.

The results were very interesting. Similar immune responses were seen after uterine infusion with PBS, seminal plasma, and milk-based extender. The least pronounced immune response was seen after infusion with egg-yolk-based extender. Essentially, an immune response is a natural response to any substance getting into the uterus. Whether it’s semen, extender, or saline, an immune response (”reaction”) is perfectly natural.

The only thing that might cause any sort of adverse reaction in a semen extender might be the antibiotics contained in the extender. In fact, we heard a very interesting piece of anecdotal evidence this week about a mare we were working with last year. The mare failed to conceive on several consecutive cycles. A reaction to the egg yolk extender was eventually blamed, and the mare conceived when inseminated with raw semen directly after a collection. This year, the mare has been treated for a minor infection, and has been found to be extremely sensitive to a range of antibiotics. Almost all commercially available semen extenders contain a broad-spectrum antibiotic, and it is fairly likely that this factor was the main cause of her failure to conceive; due to an allergic reaction of the endometrium to antibiotics.

Milk and egg yolk are fairly innocuous, and it’s really not plausible that they would cause an allergic reaction in the endometrium. If you’ve ruled out other problems, then consider an antibiotic sensitivity, but don’t blame the semen extender!

Some things to think about…

• You MUST examine the semen using a microscope before you should even consider shipping it out, or even inseminating it on-site. You can pick up a microscope for less than £100 from eBay, so there really is no excuse.
• A microscope allows you to make subjective measurements of total motility AND progressive motility. It also allows you to make a subjective assessment of velocity (normally on a 1-5 scale). It is vital that you make both motility estimates.
• Combined with a haemocytometer, the microscope also allows you to measure concentration. You MUST know the concentration of the individual ejaculate. Saying “oh, well he always produces around 200 million/ml” is NOT good enough. You must monitor concentration, not only because you need it for calculating how much semen you need to send away, but to see if there are any unusual changes to your stallions semen quality. If you don’t know how to use one, get someone to teach you, or get a cheat sheet from us!
• Extending 3:1 is the MINIMUM amount that semen should be extended for chilled shipping (in fact, the best longevity and fertility rates are normally achieved when semen is extended from around 7:1 to 9:1). The aim is to extend semen until you have 25 million progressively motile sperm in each ml. To do this, you MUST measure progressive motility and concentration. If you can’t work out the maths, then get someone to teach you, or get a cheat sheet from us!
• You should always send away paperwork containing information about how and when the semen was collected, the semen quality at the time of processing, the initial and shipping concentrations… as much information as you can give. The syringes, bags, or tubes should also be labelled with the stallion’s name & collection date and time as a bare minimum.

It’s not difficult to send out good quality semen, but when it’s done badly it damages your reputation, your stallion’s reputation, and the reputation of AI & chilled semen… Everyone should be aiming to send away the best quality chilled semen that they possibly can!

Mare owners, vets, and AI technicians… when you receive semen, make sure that the points above have been addressed. If not, then make a fuss!

The PSHP is holding a stallion parade at Hartpury College, Gloucestershire on 14th February 2009. Tickets are £10, and with 28 of the country’s top stallions in attendance, it would be well worth a visit from anyone thinking about putting their mare in foal this year! Of particular note are Ulrik Molgaard and Henriette Andersen’s Astonish and Treliver stud’s Treliver Decanter. Equine Reproduction Ltd will be collecting and distributing semen for both stallions for 2009.

No fertility data (pregnancy rates) is available, and this is important to keep in mind. Previous work had suggested that addition of cholesterol to the sperm membrane could improve freezability. However, work since then has shown that while increasing the cholesterol content of the sperm membrane does improve post-thaw motility, it actually causes a reduction in pregnancy rates. This is probably due to the added cholesterol reducing the sperm’s ability to undergo capacitation.

Hopefully we’ll see some fertility data using frozen-thawed semen from this trial at some point in the not-too-distant future.