Genetics

Opinion: Sperm morphology testing in bulls – Why all the fuss?

Sally White, Eastern Plains, Guyra, NSW., 17/05/2021

NSW seedstock producer Sally White from Eastern Plains near Glen Innes expresses her opinions about the value of semen morphology testing, and offers some compelling reasons why it is not more widely adopted …    

 

The fundamental job of a breeding bull is to get females in calf.  He’ll generate more profit, if he does this earlier in the breeding season. If the bull has an inherent fertility problem, meaning he is infertile or sub-fertile, he will not be able to do this.

Though a bull may present fat and sappy on bull sale day, with tremendous phenotype & genotype, it’s worth noting that this has no relationship whatsoever with his fertility or reproductive function.

So on bull sale day, how can I tell if a bull is fertile, infertile or sub-fertile?  The answer is simple, but little applied.  Pre-sale sperm morphology testing bulls, prior to their entry into a sale ring, is the best means to accurately identify infertile and sub-fertile bulls. It is a long established, objective measurement of bull fertility.

But even though it’s fundamental to the job of a bull – and thus, profit – it’s no easy task to buy bulls at auction out of a sale ring, with sperm morphology test results.  Why is this?

To begin, what is sperm morphology?

Sperm morphology describes the anatomy or structure of individual sperm cells.  It cannot be tested ‘crush side’.

Testing for sperm morphology requires a large, specialised laboratory microscope to examine a preserved semen sample to assess the integrity of the sperm head and tail. Test results are expressed as the percentage of normal sperm cells in a semen sample or percent normal sperm (PNS).

The percentage of abnormal sperm cells is also reported, classified into seven categories.  It’s highly likely these abnormal sperm cells will prevent conception.

Though they may make it to the site of fertilisation, the resultant embryo will be non-viable and unable to be maintained. So the female will fail to conceive on that cycle, falling into a later calving round.

The recognised minimum standard for bull fertility in Australia is greater than 70pc normal sperm for bulls used in single sire mating or AI, and greater than 50pc normal sperm for bulls used in multiple sire mating.

Sperm morphology should be not be confused with sperm motility or “crush-side semen testing.”  Sperm motility testing determines whether the sperm are progressively forwardly motile. That is, are the sperm alive and swimming ‘forward’, which is obviously important to achieve fertilisation.

Motility of the sperm is also expressed as a percentage.  The recognised minimum standard for bull fertility in Australia is greater than 30pc progressively motile sperm.

A bull may pass one but fail the other. However a bull needs to pass both to demonstrate that he is truly ‘reproductively sound’.  In so doing, he demonstrates he has a high probability of being fertile as opposed to infertile or sub-fertile.  He demonstrates he is ‘road worthy’ & ‘fit for purpose’ – that is, breeding.

Bull sale catalogue claims

Too often we bull buyers read in a bull sale catalogue, “All bulls have been semen tested”, yet actual results are not disclosed.  Moreover, if you ask the direct question, it is too common that “semen tested” reveals bulls have been crush side tested only (for sperm motility). They have not been tested for sperm morphology as well.

Without both sperm motility and sperm morphology testing, you’re no further ahead in being able to identify a bull with an inherent fertility problem.

One to two in five, are duds

Alarmingly between 20pc and 40pc* of bulls will fail a sperm morphology test, depending on breed.

Of utmost importance to the bull buyer is that those who fail are at worst infertile, and at best, sub-fertile.

So for those buying bulls out of a sale ring, where the bulls have not been sperm morphology tested, about one in five (more depending on breed) will likely turn out infertile or sub-fertile, with an inherent fertility problem.

Depending on the timing of the joining program, the cost of buying an untested bull with an inherent fertility problem may not reveal itself until up to a year after his purchase. Too often, they fly under the radar but at a cost borne by the bull buyer. This cost lies in a higher incidence of preg-tested empty females or females calving late in the breeding season.

Buyers may have observed bulls with fertility problems serving females during the joining season, and understandably, think all is well.

In a multiple sire mating in a joining program it can be almost impossible to identify an infertile or sub-fertile bull (without sperm morphology testing) as other bulls may cover for him to some extent. This extra workload for the remaining (fertile) bulls makes it more likely they may incur an injury during the joining season.

Yet more cost to bear.

A sub-fertile bull may still sire calves, but they’ll likely be costly, late calves as his sub-fertility can result in a non-viable embryo so that the female will fail to fall in calf on that cycle.

Thus she falls into a later calving round, producing a later, less profitable calf. It is difficult for the female to then break out of this late calving cycle, increasing her chances of PTE in a subsequent joining.

So it’s more probable she will end up culled from the breeding herd, though the fertility issue was never of her making.  Rather its source was sub-fertility in the bull.

Why the poor uptake in morphology testing?

So why the poor uptake in pre-sale sperm morphology testing?  Does it cost too much?  Is there a lack of understanding?  Don’t bull buyers care?  Is it a question of integrity in the seedstock industry?

All of these are likely reasons, and often more.  But I’d like to comment on a few ‘reasons’ that seem often used to argue ‘against’ pre-sale testing.

Firstly the cost of sperm morphology testing is very economical – $35/head at most. The major cost lies more in the direct cost to seedstock producers of culling those bulls who fail sperm morphology testing from their sale drafts.

If sold through the sale ring in the current market, a bull may fetch$8000/$9000, but if sold for slaughter because he has tested infertile or subfertile, he is worth about $2000/$3000.

Most likely this is the sticking point, in my opinion. But really, when buying bulls at auction out of a sale ring, it is fair and reasonable to expect them to be reproductively sound and fit for breeding purposes, at the fall of the hammer.  If not, then this is a cost that should rightly be borne by the seedstock producer, rather than the bull buyer.

Even though many seedstock vendors offer clients a credit at a future sale for bulls that may subsequently fail a ‘vet test’, the bull buyer will have already borne the cost of lost production by the time this eventuates.

What’s more, the buyer’s credit could well be used to buy another bull with an inherent fertility problem, if that seedstock vendor continues on the path of not testing sperm morphology & sperm motility.

Secondly, a common catch cry is that ‘sperm morphology varies over time’ so ‘don’t hang your hat on a single test result’.  This is 100pc true. Just like any other raw measurement, such as weight and  eye muscle area, sperm morphology is not a constant  and will change.

Sickness, disease, injury, environment, nutrition or indeed any stress arising from a production system or husbandry program (such as vaccinations) can impact on sperm morphology.

Once sexually mature, a bull is continuously producing semen throughout his life. From start to finish, when semen is ready for ejaculation, takes a production period of about 6-8 weeks. Taking this time period into account, once the bull recovers from a stress event, his sperm morphology will similarly recover, providing he does not have an inherent fertility problem.

While a subsequent test result may vary from a former, ‘good’ sperm morphology has been shown to be repeatable in a reproductively-sound bull which is without an inherent fertility problem.

Varying results from lab to lab?

Thirdly, some argue that as sperm morphology test results can vary from laboratory to laboratory, they cannot be considered a reliable indicator of bull fertility.

While results can vary by laboratory, this can be mitigated. If testing is carried out at labs with comparable equipment (some brands of microscope are better at detecting abnormalities in the sperm than others), staff are of equivalent competency (is the morphologist experienced, qualified & trained, doing this kind of work on a daily basis) and if results are reported in the standardised format according to the national guidelines for classifying sperm abnormalities, it’s unlikely the variation in results between labs will be so substantial as to render them null and void.

The reality is a sperm morphology test result is not a guarantee for fertility in the bull, as there are so many factors that can either permanently or temporarily affect bull fertility.

But this in no way discredits sperm morphology as a reliable, accurate measure of bull fertility. Pre-sale sperm morphology testing of bulls will weed out the true losers when it comes to fertility which crush side semen testing on its own will not.

These bulls do not belong in a sale ring.  Pre-sale sperm morphology testing is the best means currently available to substantiate that those bulls entering that sale ring have a high probability of being fertile, do not possess an inherent fertility problem (that will not correct itself over time), and are not infertile or sub-fertile.

Multiple industry funded, published, formal, peer reviewed, scientific research papers stand behind this claim.  It is not a smoke and mirrors ‘marketing tactic’ or subjective opinion.

Surely this is ‘bread & butter’ stuff for bull buyers & the seedstock industry?  The lack of widespread uptake is a continuing industry wide cost though there is a means to readily address it.

So in future, I encourage bull buyers to ask the specific question of their seedstock producers: “Are sperm morphology results available for these sale bulls?  If not, then why not?”

Be proactive and have the conversation.  You’ve much to gain.

 

*Felton-Taylor, Prosser, Macrossan, Perry (Theriogenology 2020)

 

 

 

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Comments

  1. Haydn Shipard, 10/06/2021

    As with Rob Richmond, I have over 36 years in the semen production industry and I agree with Rob on the non use of semen morphology testing of sale bulls.
    Two important factors would need to be introduced if testing was implemented.
    1. All bulls would need to be worked before testing, to ensure the bull is given every possible chance of passing this test. Cleaning or starting his sexual life.
    2.An electro ejaculator not be used for collecting. The stress put on the bull with inexperienced, incompetent technicians is a concern. A bad bull response can mean a poor or no sample.
    As Rob has found, I have collected and successfully processed semen from numerous bulls, that the previous professional had advised to cull. And after just one crush side evaluation.
    The industry – both breeders and buyers – do not take enough care in preparing bulls for the job they are destined to do.
    Young bulls, weaned, fed, then prepared for a sale, then you expect him to produce excellent semen, by putting an electro up his rectum.
    Same with old bulls, straight out of a paddock into the cows.
    Small testes, bad feet, bad structure and temperment, I feel are of a more important issue I am being presented with when collecting semen from bulls, that the industry should be paying more attention to.

  2. Robert Richmond, 26/05/2021

    Sally my whole career of 47 years has been involved in the artificial breeding industry.Besides being a part of my profession collecting semen from bulls and freezing semen is a major interest.I have fertility tested 000’s of bulls in my career and collected and frozen semen from an even greater number.I dont consider myself an expert but perhaps my experience qualifies me to comment on your article.
    The basic question I ask is where did you get the information to make such definative statements that morphology testing is a must?
    My experience is I have never had a complaint in 47 years of testing bulls that I made a judgement on a bulls fertility that was not correct or in reality the bull did not give satisfactory conception rates.
    Your comment about microscopes affecting the accuracy of the morphology test is not correct.The reality is a colleague of mine recently sent samples of the same batch of 33 bulls to 4 different labs and the results were very different.One lab says “cull the bull”,another lab says the bull is fine.There is a huge error in assessment and I dont think this can be overcome.
    I strongly disagree that breeders adopt morphology testing as standard practice,I would actually say do not use morphology testing as standard practice.
    Testing semen whether it be crush side testing or Morphology testing depends a lot on the experience of the person making this assessment.There are many variables and dare I say many experts.Last week I semen tested 2 high genetic value and dollar value bulls that the breeder was told to cull by a professional nominated to semen test bulls for that sale.I had no problem giving both bulls a very positive semen quality report.One bull produced no semen at the sale test and I was able to get 22mls of good quality semen.
    Sally you are a passionate and excellent breeder of cattle but please do some more research before you write articles like this.
    One of the worlds most qualified people to talk about this subject is Dr Peter Chenoweth from Chenovet may I suggest you contact Peter for comment or phone me on 0407211087.

    • Sally White, 09/06/2021

      Dear Robert (Richmond),

      Thank you for your comments. I am pleased this opinion piece has generated some engagement & genuinely appreciate that many including yourself, took the time to make public comment. My piece was clearly submitted as ‘opinion’, so I too, make no claim to being an expert in this field.

      I would like to respond to some points you raise.

      Firstly, when compiling my opinion piece, I consulted quite a few published articles on the topic of bull fertility as well as websites, notably futurebeef.com.au. They include but are not limited to:-

      1. Male indicator traits to improve female reproductive performance.
      2. Bull breeding soundness, semen evaluation and cattle productivity (by P.J. Chenoweth, F.J.McPherson).
      3. Bullpower – Delivery of adequate normal sperm to site of fertilisation.
      4. Effect of breed, age, season and region on sperm morphology in 11,387 bulls submitted to breeding soundness evaluation in Australia.
      5. Markers and genes influencing puberty.
      6. The North Australia Program – 1998 Review of Reproduction & Genetics Projects.
      7. Associations between sperm abnormalities, breed, age, and scrotal circumference in beef bulls.
      8. Proceedings of AVA Annual Conference, Brisbane, 2018 – A refresher on sperm morphology.

      The take home message I gained from these is that when taken together, sperm motility & sperm morphology are an accurate & reliable measure of fertility in the bull, more so than simple crush-side, sperm motility testing on its own. Sperm morphology can change over time & no two tests will give the exact same result, but regardless it remains a good indicator of bull fertility & is repeatable in a reproductively sound bull.

      I well acknowledge that there likely exist “high dollar value bulls” who may initially fail sperm morphology testing but who then go on to produce “good quality semen”. But I see this does not flat-out discredit sperm morphology as a measure of fertility. Rather, it raises more a question of why the reason/s for failure? Presumably, “good quality semen” was established by both sperm motility & sperm morphology testing? Did the repeated failure in sperm morphology manifest itself in the same sperm abnormality presenting in samples? Did a pre-existing veterinary health condition contribute to the poor sperm morphology result? Even for a “high dollar value” bull, it could well be that it is cost prohibitive to fully diagnose & treat a veterinary health condition. Instead, the bull is simply given time to recover, following which, he is then able to produce “good quality semen”. So it was not that the sperm morphology test results got it wrong, but rather they reflected a veterinary health condition, albeit undiagnosed. In that state of (poor) health, it is fair & accurate to say, the bull was not fertile nor fit for breeding purposes, which the (failed) sperm morphology results attested to.

      It could well be that in some cases, these bulls who may go on to produce “good quality semen” at a future point in time, are ‘mistakenly’ sold for slaughter rather than breeding purposes, all because of failure to pass pre-sale sperm morphology testing. They end up ‘lost’ to industry & the breed, their breeding potential unrealised. But the reality is that at an industry or breed level, the genetic cost of losing these individual “high genetic value” bulls can well be borne. Though I do acknowledge it is does come at a cost, is unfortunate & a bitter pill for the seedstock producer to swallow (& I have swallowed them!). However, I too am a bull buyer & consider it unreasonable that I bear the full cost of assuming this fertility ‘risk’ which could be mitigated, to some extent at the very least, by pre-sale sperm morphology testing bulls.

      In the course of selecting AI sires, I have spoken to many semen selling companies about obtaining sperm morphology test results for AI sires in their catalogues. All assured me on multiple occasions, semen samples from bulls are routinely tested for sperm morphology as part of their ‘quality assurance’ procedures. If so unreliable & inaccurate, I wonder they bother to test at all? Do you advocate they too, “do not use morphology testing as standard practice”? However, I add that almost all decline to share results, citing issues of ‘commercial-in-confidence’ & similar (?).

      Finally, I would like to advise that I have indeed previously spoken to Dr Peter Chenoweth regarding sperm morphology, as well as consulting an article he co-authored, along with some other “qualified people” on this topic. This was well prior to submitting my opinion piece. Though my conversation was not in the context of the merits or otherwise of pre-sale testing, I understood it, that all spoke in favour of sperm morphology as a measure of bull fertility.
      Sincerely,
      Sally White.

    • Carina James, 08/06/2021

      Agreed!

  3. Steve Reid, 25/05/2021

    There are multiple semen testers across the country doing crush side morphology tests. What is the accuracy of these tests?

  4. Tracy Sullivan, 23/05/2021

    Well written and spot on Sally!

  5. Kim Kelly, 22/05/2021

    This is a comprehensive and factual article and I applaud Sally on highlighting the inadequacy of simply crush side testing bulls alone. Fertility predictions are just that – compiling as much information as possible about that bull will only improve confidence in its fertility. Absolutely should apply to frozen semen also.

  6. david johnston, 21/05/2021

    Nice job Sally….and there is more! PNS in beef cattle is heritable, particularly in our tropical breeds. This means a component of the trait is genetic and therefore passed to the next generation. So it can be improved by selection and conversely, poor PNS can be passed to future generations. But like all raw data it needs to be turned into an EBV before it has value as a selection tool. And, if this is done there is further benefit that PNS is also genetically related to improved female reproduction.

  7. Viv, 19/05/2021

    Excellent article very well explained Sally

  8. Lachie wilson, 18/05/2021

    Sally a very well considered article.
    I believe there are two key reasons for the slow uptake of morphology testing particularly in bos Taurus breeds.
    1. Inconsistency of results from different labs. I am aware of the same sample collected under veterinary supervision and submitted to 3 different reputable labs. The results were wildly different with no consistency from lab to lab. To me this suggests the test is subjective not objective as the standardisation training/guidelines is obviously failing.
    COME ON CATTLE VETS RAISE THE BAR make sure your supposed Bull check system is backed by the highest level of quality assurance. I believe this has been tabled at a recent cattle vets meeting so let’s hope the issue is addressed. This is limiting the uptake of morphology testing as many bull breeders have no faith in the assurance of the testing labs and are wary of bulls getting culled unnecessarily.

    2. A motility and morphology test is only a snapshot of time. You can not decide a bulls fate on one test only. Many bulls will come good over a 2-6 month period maybe longer.

  9. Rob Atkinson, 18/05/2021

    Totally agree Sally.
    If you want to maximise preg rate, morphology test is a must!

  10. Rob Introvigne, 18/05/2021

    To say 1 out of 5 bulls in a sale ring would turn out to be infertile if they were not morphology tested is not true.
    If you do a crush side test and follow with a morphology test you will may only 3 to 4% fail the first time.
    You can test a bull 6 times in 6 months and can get a different result each time that is why some breeders are reluctant to do morphology testing because a lot of good bulls get there head cut off for one failed test.
    If you are having trouble with infertile bulls change where you buy your bulls from or change breeds.

    • Tracey Gowen, 19/05/2021

      Hi Rob,

      I would very much question whether anyone has culled a bull on one failed test. If so it is a wild overreaction.
      All accredited vets would advise re-testing that bull, as defects can be transient and/or the result of injury, infection, or just a dud sample.

      It is important to view the issue of variability of results at different time points through the right scope – if a bull passes a morphology assessment, it does not ensure he will ALWAYS pass a future assessment. Rather it indicates that he was, at that point, fertile and the vendor has done their due diligence in ensuring the bull they are selling is capable of fertility. If a bull fails on his first test but passes a retest, he is still capable of being fertile and can be used with confidence.

      I know many studs who do not perform morphology on young bulls, particularly yearling bulls, because they argue they are too immature and would fail, but once they reach full maturity they will be fine. The vendor had absolutely no way of knowing if this will be the case! Certainly, immature bulls will often fail morphology testing, but isn’t that an even stronger reason to be testing – they are selling you a bull that is not yet fertile, and may never be! They cannot guarantee the results are only due to immaturity and not a permanent fertility issue.
      Further, bulls which mature at a later age will have daughters which reach maturity later, so may be harder to breed as 16 month old heifers.

      Sally I think this was an incredibly well-written article, thank you!

  11. Paul+D.+Butler, 17/05/2021

    Just to fuel the fire………Dr. Roy Ax of Arizona did research decades ago that showed even with motility, morphology and sperm count bulls that tested good……..there was great variation in those bulls ability to fertilize ova.

  12. Dr+Sandra+Jephcott, 17/05/2021

    Regarding variation of morphology lab to lab, it is minimal to non – existent in Australia as all morphologists are regularly tested on an accreditation scheme. If they fail, they are no longer accredited to test bull semen under the Australian Cattle Veterinarian’s Bull Check scheme. If an accredited veterinarian is used to test the bulls, he or she will use an accredited morphologist for semen morphology. It is important for quality insurance and to be confident that a stud is selling fertile bulls, a Bull Check accredited veterinarian must be used to fertility test sale bulls.

  13. Ashley Kirk, 17/05/2021

    A very well written article Sally!! Made complete sense to me.

  14. Greg brown, 17/05/2021

    For once some very needed honesty, and from a stud person

  15. Greg Popplewell, 17/05/2021

    Well said Sam. Further more the frozen semen industry needs to adopt Morph as standard QA.

    • Sally White, 19/05/2021

      Absolutely!! But it is almost impossible to get sperm morphology test results from semen companies. Despite my repeated requests for same, the usual reply is “our standards are among the highest in the industry but we don’t release test results”. The scant few results I’ve received related to testing conducted 2 years prior to the time of my request. But this is no reason to quit asking for them!

  16. Joanne Gowen, 17/05/2021

    Good on Sally.
    We need bull breeders to provide transparent information and above all to provide as much information as possible and that includes pre-sale semen morphology testing of all bulls in the catalogues. Some studs only test bulls that they may think of using in their herds. Come on, your buyers deserve the same consideration and respect.
    Bull buyer should not have to ask breeders for this information, it should be offered as a matter of course.
    The issue of credits offered is another matter – perhaps Beef Central can cover that in an article too.

  17. Alex+McDonald, 17/05/2021

    Very good analysis based on science Sally

  18. Peter Vincent, 17/05/2021

    An excellent article and excellent advice from Sally White.

  19. Ian McLean, 17/05/2021

    Excellent article, well done.

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