GetBreeding

Even if you’re collecting semen from a stallion who is on the same site as the mare, and you’re putting the semen straight in, you should still extend the semen 1:1 with an extender that works well with that particular stallion’s semen. It will improve longevity of the sperm cells that you inseminate, and should, in most cases improve pregnancy rates.

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

Over the last month or so, whilst we’ve been training people to collect, assess, and ship semen, we keep seeing the same thing:

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!

Wikipedia states: “Lies, damned lies, and statistics” is part of a phrase attributed to Benjamin Disraeli and popularised in the United States by Mark Twain: “There are three kinds of lies: lies, damned lies, and statistics.” The statement refers to the persuasive power of numbers, the use of statistics to bolster weak arguments…

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!

Well, we’ve certainly written about this before, but it’s worth covering again before we get going with the bulk of the AI work this season.

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!

DNA damage might be one of the reasons that frozen-thawed stallion semen is less fertile than chilled or fresh semen. A group from the University of Northern Colorado (Burns et al, 2009) have done some interesting investigations where they have been adding plant extracts to commercially available freezing extender. Initial results with 4 stallions shows that additions of these extracts appears to significantly reduce DNA fragmentation that occurs during the freezing (and thawing) process.

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.

There are a huge range of fertility supplements available for stallions… all sorts of feeds, powders, liquids and gels which promise to improve your stallion’s fertility. The problem is, that the majority of these supplements are based on (or are exact copies of) human fertility supplements. There is little to no proof that human fertility supplements will have any positive effect on stallion fertility.

In fact, there is a growing body of evidence suggests that dietary supplementation of antioxidants (where no deficiency exists) has no effect on fertility whatsoever.

The only dietary supplement component that currently has any peer-reviewed research proving that it benefits stallion fertility are the Omega 3 & 6 oils. Data on it is currently limited, but there is research and anecdotal evidence suggesting that supplementation with these oils can improve freezability of some stallion’s sperm cells.

If you’re planning to have semen frozen from your stallion this season, and want to use any dietary supplement to try to improve fertility, you must remember how long it takes to make a sperm cell. The process of turning a germ cell into a fully fledged and fertile sperm cell takes around 57 days. So for the supplement to make any difference, you need to be feeding the supplement for around 60 days, and then keep going through the breeding season.

If you want to try Omega 3 & 6 for your stallion, we suggest you try NAF’s Omega Oil. It’s an affordable way to supplement your stallion’s diet with these oils.

Spermatogenesis, the process by which sperm are produced, takes approximately 57 days.

Daily sperm output in the stallion averages 5 billion.

In the height of the breeding season, sperm release rates average up to 70,000 sperm per second!

An ejaculate from a sexually rested stallion will contain 10-20 billion sperm.

Masturbation is perfectly normal and natural in stallions. In fact stallions will masturbate every 90 minutes on average.

Equine sperm velocity normally ranges from 50-120?m/s (micrometres per second).

It is hypothesised that frozen stallion semen could be viable for up to 10,000 years or more (if stored correctly).

The stallion produces 70,000 sperm cells are produced every second in the height of the breeding season!

Hope you enjoy those facts and figures!