Hi everyone, welcome to Tibet today's, webinar, where we're gonna talk about some reproductive strategies to improve cattle performance. We're gonna cover quite a lot of material today, and it, it, it's not intended that this is gonna give you all the answers to all of these strategies, but. Hopefully it will, sort of give you an idea of what is available out there to help your farms, and maybe point you in some directions of, of areas for further study, if you feel that you want to utilise some of these strategies.
OK, so we're gonna start the, our learning objectives are gonna be that, you know, we, to, to think about the strategies we're gonna put onto files, we need to understand the basics of cattle reproduction. Then we're gonna talk about some of the problems that are associated with fertility and beef and dairy enterprises. We're gonna look at some of the common methods that are used, improving cattle fertility, but then also using estimated breeding values and the use of genomics to improve the herd.
And then also because we must never forget about the bull, thinking about the importance of the bull and breeding soundness exams, and that's going to be particularly relevant for beef farms. OK, so, Easter cycles, so puberty and heifers generally occurs around 7 to 18 months and with most enterprises aiming to, carve those heifers when they're 2 years old. However, puberty can be affected by various factors, breed, nutrition, growth rate, and disease, and we'll talk a bit about that later on and, and how we can check that our heifers are, are ready to be bred.
These recycling cows, cows, after they calve will begin to cycle 20 to 30 days, but this can be extended in high yielding cows or those who have had the disease post calving, and sometimes those first signs of east just are suppressed, particularly in beef cows where the calf is still at foot suckling. So cows are non-seasonal polyester breeders. As we said, the cycle is around 21 days, but the range is between 18 and 24.
So it's not always gonna fall exactly on that 3 week period. And generally, cows have 2 to 3 waves of follicular development per cycle. There is a, when we have cows that have 3 waves of fol follicular waves each cycle, it's potentially likely that those animals will be, more fertile, because those follicles are younger, and therefore healthier.
And actually a lot of the breeding strategies we're gonna talk about later will aim to push those cows into having a sort of 3 follicular waves per cycle. After the the onset of Eres, there will be ovulation, generally 30 hours, after that, and. We're really aiming to to have the semen in the cow prior to ovulation, because if it, if it does go in after, there is less chance of a successful fertilisation.
So you'll all have seen pictures and graphs like this, if you do fertility work, or you might remember it back from your, your days as a vet student, and this is just representing what's going on on the ovaries. So the top half of this graph at the top is, is a CL developing and then regressing, and then the bottom is a pic pictogram of the follicular waves. So we get, Three waves and only the last one does the the follicle achieve dominance and and ovulate because it coincides with the regression of a a corpus luteum.
And when that corpus luteum regresses, we're gonna get a surge of LH, which is gonna push that follicle to luteinize and ovulate. Again, lots of different hormones intermingling, and we're not gonna spend a lot of time looking at these. This is really just to refresh your, your memory about, about what's happening in the cow, and we're gonna talk a bit about all these specific hormones, where they act and what they do.
So, what is the basic timeline? It's represented in those pictures, but, just sort of from a, from a, a text point of view, the cow's gonna ovulate. There's a depression left, which is the cor corpus hemorrhagicum, and a new group of follicles will begin to grow.
All those follicular waves that we talked about will be preceded by an increase in follicle stimulating hormone. The corpus hemorrhagicum will become the corpus luteum. The corpus luteum will secrete progesterone from day 5 to day 18.
So if we're thinking about using hormones to utilise a corpus luteum, we're not gonna, it's not gonna be responsive for sort of 5 to 7 days after it forms. One follicle will become dominant, that's gonna cause the regression of the other follicles. The dominant follicle will secrete estradiol, and because there's still that CL there, it's not gonna ovulate.
So that first dominant follicle will become non-functional. There'll be an increase in follicle stimulating hormone, and we'll get a second wave of follicles, and the same thing will happen. That FSH is controlled by oestradiol in an inhibit, which is secreted by a dominant follicle, and as that concentration of oestradiol, increases, so will the concentration of or the sorry, the concentration of FSH will decrease.
That will lead to luteinizing hormone being secreted in pulses. And again, that dominant follicle may not ovulate, if the hormones aren't at the right level. However, when a dominant follicle is sufficiently developed and produces sufficient estro diol, it can cause an LH surge.
This pul pulsatile nature of LH will increase until it leads to ovulation. That dominant follicle will only proceed to ovulation if the CL that is present at the same time regresses. And that's only going to regress by the release of prostaglandin from the uterus.
So there's a lot of intermingling factors that have to happen for a successful ovulation. And, you know, when you think about it like that, and then you think about all the other factors that affect fertility and health in cows, you know, there's a, there's a lot that we're asking these cows to do. Again, this, diagram from Arthur's veterinary reproduction of obstetrics just sort of shows all the different players in these hormonal cycles.
So all the different parts of the cow that are releasing hormones and producing hormones, and the areas that they are having an effect on. So as you can see, it, it's a multi-system, multi-system role, so. If we have other disease, that's gonna have an impact on fertility, .
So again, in a modern dairy cow, particularly where we're asking and putting a lot of metabolic demands on them, they may struggle with fertility. So what are these hormones? What do they do?
So fol follicle stimulating hormone is a gonadotropin secreted by the pituitary and acts on the ovaries, and that is just to cause maturation of the ovarian follicles, so leading to the growth of those. We can use exogenous follicle stimulating hormone and that can causes ovulation, so the development of multiple dominant follicles. The other important hormone, luteinizing hormone, again a gonadotrophin, again secreted by the pituitary, and again it acts on the ovaries.
And that's gonna stimulate faecal cells, leading to the secretion of testosterone, which is converted into oestrogen by granulosa cells. When we get ovulation of mature follicles, it's gonna be it's induced by that pre-ovulatory LH surge. So the postsatile nature reaches a limit where it causes ovulation.
And LH is required for the continued development of function of, of, of CLs. How do we control gonadotropins? So in the body, gonadotropin releasing hormone is the principal regulator of those, and that's, synthesised and secreted in the hypothalamus, and binds to receptors to stimulate the secretion of LH, and FSH.
When it stimulates secretion of LH, that stimulates gonadal secretion of testosterone, oestrogen and progesterone, but it. Which then in turn has a negative feedback effect and inhibits the secretion of GNRH. So There's a sort of self-regulatory loop, leading to the post pulsatile secretion of LH and FSH and those will very much dependent on the stage of the cycle.
And lots of different hormones and, and we'll see some diagrams later, will have an an influence on GNRH secretion. Progesterone, a really important steroid hormone, and it has a variety of functions, but the main one is that it will promote, pregnancy, and once, once a cow, once a cow is conceived. But it will also convert the endometrium to its secretory stage, which helps prepare the uterus for that, embryo to implant.
It thickens vaginal epithelium, a cervical mucus, It mitigates the tropic effects of oestrogen, during implantation and gestation, it will, reduce the maternal response to allow acceptance of the pregnancy. It decreases contractility of the uterine smooth muscle. So therefore, again, helping to maintain pregnancy.
And then when progesterone falls at the end of pregnancy, that will help initiate part tuition. Estradiol, another steroid hormone, helps not only in the development and regulation of the female reproductive system and those secondary sex characteristics. But it also helps the maturation and maintenance of the vagina and uterus.
It's obviously involved in ovarian function and the maturation of follicles. It regulates gonadotropin secretion and therefore has a direct impact on fertility cycles. It will, has a role in libido, so oestrogen, promotes the science of estrus, and alongside growth horn, hormone also helps in mammary development.
Prostaglandin, we talked about very important in, in, in causing the, the regression of CLs, and it's produced by the uterus when it's stimulated by oxytocin. So that might happen when there's been no implantation, during the luteal phase. So, again, to get the, the animal cycling again, by causing lutolysis of the corpus luteum.
And the action of prostagland is dependent on the number of receptors on the CL, so that's why we talk about the CL not being responsive immediately after it's been formed. So that's particularly important for misalliance. You know, we've all been called out to go and see, you know, young animals that have been caught by a bull.
Well, you know, if the bull is still in with them and they've been caught in the last couple of days, they're not going to respond to our, our prostaglandin injections. So, after that very rapid, talk about the hormones, does that, does that make this graph make more sense now? And I suppose the important thing is, you know, does that matter when we're thinking about what, what we as vets are doing, and, I suppose the answer is sort of in the, we need to understand what's going on so that we can implement the correct, strategies, but.
As we're gonna talk about later, a lot of the, the strategies and protocols are established and actually in a way, don't really matter at what point of the cycle the the cow is at. We talked about the interactions of these hormones and, and here you can see, you know, we've got positive and negative feedback. So our estrogens having a positive impact on, on, GNRH, progesterone having a negative impact, and, .
The, so again, all of these hormones are helping to regulate each other, so deficiencies in one or or problems with one will stop the, the cycle functioning. So, we've talked a bit about the role of oestrogen in in promoting stress and, and by far one of the biggest factors, I think, in poor fertility on farms is failure to observe, identify yeast stress in the cows. Now, in the UK most dairy cows are bred with artificial insemination.
So if you're not using sort of fixed time AI protocols, you are relying on the identification of heat. And therefore poor heat detection can have major effects on on the herd's fertility. And whenever I find a herd which has poor fertility, I always think, one of my first questions is always, you know, how are you detecting heat?
And even if they say, you know, they're using automated, automated devices, you know, are they interpreting those correctly or is there a reason why that might not be working? So errors in heat detection can come in two ways. They're either we miss cows that are in heat or cows are being identified as they, as being in heat when they're not.
Missing cows in heat, what will that mean? That will mean we get fewer eligible cows submitted for service. And when we look at the data, we will see more cows, in within intervals, service intervals greater than 18 to 24 days.
If we're misidentifying cows, we could have more cows submitted for service, because we're submitting cows that actually aren't in heat, but the interval between heats may be, may be shorter. So when we talk to farmers about how they're identifying heats, we need to remind them of what sort of the, the cardinal signs of of Eastres are, and there is only one definitive sign, and that is that a cow is standing to be mounted by other cows when they're free to move away. And that when they're free to move away is a very important sort of adage, because in some situations, you know, in a collecting yard prior to milking, or if there are cubicles, .
If the cows are in cubicles, then actually those cows might not be able to, to move away when when a cow mounts them and it doesn't necessarily mean that that cow is in heat. We talk about a lot of other signs associated with heat behaviour, but they are only suggestive of a cow being on heat. And those include, you know, attempting to mount other cows, if they're mounting head to head, .
It doesn't happen that commonly, but again, if the cow that's being mounted isn't moving away, that could be a primary sign of heat. Cows can be restless, they can vocalise when they're isolated. You can sometimes see small increase in body temperature.
They might have poorer milk letdown, or you might see a pulling string, a clear pulling string from the vulva. If you see sort of the post yus bleeds, so a blood-tinged thick mucoid discharge, it generally suggests that you've missed an estrus by about 48 hours. So when I see these, I will say to farmers, you know, start looking again in 2 weeks' time for signs of heat in that animal.
When should we detect heat? Well, they can, cows can demonstrate heat throughout the day. There's no particular time where, where they're more likely to.
So if we're relying on only set times of the day, say, milking or feeding, then we might see more mist heats. It's always best to, to monitor cows when they are sort of just, relaxed. If you, if you try and monitor them when they're feeding, or they'll be distracted by the feed, if you try and monitor them while they're queuing to be milked again, it's, it's not the most natural situation, so you will probably not get many, as many cows, demonstrating heat signs.
So we should be looking at them when they're at rest. It might be that we don't actually er observe directly those advert signs of heat. So, what's a good heat detection strategy?
Ensure that all cows are identifiable at a distance, so with good clear brand numbers or clear collar numbers, . After morning milking, monitor them for sort of 2 hours, then do an early, early afternoon check, and then check after afternoon milking for another 2 hours. You shouldn't be walking around.
The farmers shouldn't be walking around the yard, it should be a quiet observation, nothing else going on, to give the cows every chance to exhibit normal behaviour. Put any served cows back to the milking herd as soon as possible, because cows that come into estrus may show that those served cows are returning sooner than, than, than a vet check might. And just make sure that all records and and observations on the farm are kept accurate.
Why has heat detection become so challenging? The main reason is how we've developed the modern dairy cow, and the modern dairy cow has a reduced period of, of, the avert signs of estrus. So we used to sort of talk about a cow would show visible signs of estrus for 12 hours.
It's actually probably more now around 8 hours, if not less. And the intensity of those easter signs has also decreased. So we're seeing less obvious signs for less time, so it is harder to identify visually.
And there could be multiple factors er responsible for that. So increasing milk yield has led to shorter heats, er, more year-round calving has led to reduced intensity, and also there will be fewer cows in heat at any given time, so less cows to demonstrate heat on each other. The increase in cubicle housing has led to an a reduced intensity, and also, difficult to see heats as obviously in confined spaces, as well as those misidentifications when cows can't actually get away from other cows.
Longer milking times, you know, whether it's just larger herds or, 3 times a day milking mean that there's reduced time available to exhibit heat. And then also age, how they are in the herd, lameness, mastitis, any negative energy balance, and how good the flooring is may also lead to, cows showing reduced signs of heat. And if we can't detect heat stress, and we're relying on that to serve our cows, then we're not gonna get them, in calf.
So, as I mentioned, now we're looking at the duration of east just being sort of at the lower end, more towards 8 hours, but actually cows will only stand for east just for maybe 5 hours. And there will be a proportion of cows that are gonna show no signs at all. So there are lots of metrics that we can do, and I'm not going to spend a lot of time on this, you know, any anyone working with large herds will be looking at data.
And we'll be aware of how we can calculate these different rates to see how our, our farms are doing, and it's always worth, you know, benchmarking your farms to the UK standards or similar other farms so that we can sort of show farmers where they fall, amongst herds of, of similar size or or similar type. There are now lots of east stress detection aids, and I suppose the fundamental thing with those is what are we, what are we achieving with them, and does the farmer understand the, the information that's being given to them by those aids? And, you know, these will be things like tail paint chalks or the heat mount detector beacons, teaser balls are very accurate and sensitive, but you do still have, then have to maintain a ball on the farm.
And they can spread venereal diseases. We can use milk progesterone to monitor the cycles. We can use activity monitors, whether those are pedometers or collars, The price of those has come down as they've become more popular, but they do require a computer system that that speaks to them and staff that understand what the, the different, outputs mean.
You can get external technicians, so some of the AI companies offer services where their staff will go and do estrus detection. And that's great. It's an independent sort of worker, but it might mean that the farm don't bother to do any of their own estre detection and that independent, technician is, is only gonna visit the farm once a day when they're doing the AI.
So when are we gonna serve our cows in relation to estress? We really need to know when they started standing to be mounted, . And then we can serve them sort of 8 to 12 hours afterwards.
So, you know, the AMPM rule was first described in 1944 and it still is really the, the, the best and simplest way of thinking about it. If you observe a standing estress in the morning, that cow should be served in the afternoon. And if you observe a standing estress in the afternoon, the cow should be served the next morning.
The optimal time for AI is about 8 hours after we've seen those signs of estrus. So, 8 hours after standing estress. As I mentioned earlier, it is always better to serve a cow too early than too late, .
And if we do serve cows after they've ovulated, then we are gonna get poorer conception rates. So why do we want to manipulate East stress? So, you know, the, the whole point of this talk is thinking about those repro strategies to improve herd fertility.
And we've talked a lot about, you know, the very basics of what's going on on the farm and, you know, what's happening, in the normal situations, but what are we aiming to do when we start manipulating estress? Well, I suppose in beef cattle. What the aim is, is for a combat breeding season, with a short calving season.
Easier to manage, better for the farm workers, easier to plan feeding, . And, and generally just, yeah, ease of management. But it also means if we can, get all our cards out in a similar time, that when we aim to sell those, they're gonna be a uniform group, which means they're more marketable, whether they're sold through the market or, or they're gonna grow at similar rates, and you're gonna have a much more standardised, product at the end.
If we are manipulating east stress, it gives us the option to use more AI, and that is becoming more popular in beef herds as well, you know, it's been used in the dairies, it's all used in dairies a lot, but beef farms are definitely taking it on board as well. And AI can really help beef farms to improve the genetic merit of their herds, but also it can limit the spread of infectious diseases. There are still bee farms that are sharing bulls.
There are still bee farms that will buy mature bulls and, and, and not look into disease status. And we're not just talking about reproductive disease, but any herd diseases where, you know, if you have a naive herd and, and you bring on a bull that has, an infectious disease, that is gonna have a massive impact on, on your herd, and, and could cause you ongoing problems. Eer manipulation also allows us to think about embryo transfer, because we'll use it to manage donors and recipients, and we'll talk a bit about embryo transfer later.
And it also helps us, where we talked about, you know, cows that have calves at foot, they may have suppressed stress, or, or the suckling calves may have an effect on, on those hormonal cycles. Well, actually, we can manipulate estrus to, to help, push cows to come cycling again. Whereas in dairy cattle, it will help us to get one calf per cow per year, which is, is, is our aim, and it will give us, the ability to either get continuous milk production.
Or we can plan lactations in the herd to meet market demands. You know, we work with farms where the buyer knows they have a reduced amount of milk available at certain times of the year, so they will pay a premium if this farm can produce milk at that time. So we can, you know, synchronise east just in cows to, to increase our, our milking numbers for, for that time of year.
We can also mean if we, if we don't need staff to monitor re, there's reduced staffing demands, but means that staff can go and spend time doing other things, maybe checking lame cows or or cleaning, cleaning out pens so that we reduce the other issues that we see on dairy farms. And again, it does give us the option of embryo transfer as well. We also need to think about some of the, problems, that we see in cows, and, by treating these problems, we're also manipulating stress.
So when we think about beef cows, there can be a high incidence of postpartum anestrus, and again anestrus is It's quite common in in cows with calves at foot. So we can reduce those problems. From an ester detection point of view, smaller herds, with a high.
Percentage of cycling cows, we may want to, use east risk management to reduce those problems as well. So, in cattle, in dairy, in cattle with active ovaries, we can manipulate, the just cycle through prostaglandins or prostaglandins with GNRH and progesterone devices. And then if we have herds with high levels of ovarian inactivity, we can use combinations of these hormones as well.
So, you know, we've got lots of weapons in our armoury for infertility in both beef and dairy. We just need to work out what are the best protocols to use for the different farming systems. So what is anestros?
Anestre is if estrus has not been observed in a dairy cow by 60 days postpartum, and we define that as postpartum anestrus. But generally, if a cow's not observed in estrus, either because she's not cycling or because he just was not detected, she may be highlighted as an anestrous cow. But it's a true anestros only if the cow has inactive ovaries, so it isn't cycling.
Subeastre could be a term used to describe weak or absent east stress behaviour, and that would mostly be due to either poor east stress detection or, as we've said, these suppressed stress signs. A classification from Wilbank in 2002 was that anestros is the anovulation with follicle growth up to the emergence stage. So cows will exhibit very small follicles.
It's common in cattle with poor nutrition, and they believe that the underlying cause was an inadequate FSH stimulation. But if you have an ovulation, but the follicles are growing up to the deviation fades, then it's because follicular growth is taking place and pro proceeds through to emergence and deviation but doesn't lead to ovulation. So that's gonna commonly occur in the past postpartum period in lactating dairy and suckled beef cows.
So they are cycling, but because of the because of the lactation or the suckling calves, er those follicles aren't gonna ovulate. You may also get small ovaries with no functional structures, but they do show continuing, follicular growth, but never to dominance. And then you can get an ovulation with follicle growth to ovulatory or a larger size of follicle, and, and that is what's really become sort of known as cystic ovarian disease.
The the contributing factors attributed to anti stress are the You know, we get fewer than 10% of dairy cows will fail to ovulate by day 40 postpartum, but in beef cattle that can be up to 60%. And that's due to the suckling, nutrition, and season. But the main factors contributing to anest stress are nutrition and body condition, calves of fert and lactation, previous dystopia, breed of the animal, age of the animal, or, or, a concurrent disease.
And when we look at it, when we look at the data, poor nutritional status and negative energy balance are responsible for the majority of any stress problems in cattle, and I think we put nutritional status and energy balance, you know, at the top of our causes of the majority of problems, definitely in dairies, but to beef in some degree as well. So we mentioned there about cystic ovarian disease, where we've got, you know, structures present, but they are not regressing, . And In cows, it's usually seen in the first two months post calving.
Although for any of you doing lots of dairy work, you will be, you quite commonly see cystic, structures, throughout lactation. And Cystic ovarian disease has been traditionally defined as an an ovulatory follicular structure with a diameter greater than 25 millimetres that persists for 10 or more days. There shouldn't be a functional corpus luteum as well.
So if you think you've identified a cyst and you find a CL on an ovary as well, it is not a cyst. And they're accompanied by abnormal ly stress behaviour, so that could be irregular east stress intervals, nymphomania or anest stress, depending on the type of cyst present. So it is an anovulatory condition.
The dominant follicle from the previous follicular wave stays and does not ovulate. Therefore, consecutive follicular waves don't reach ovulation. And what we find with cows with ovarian cysts will have no ovarian follicular waves similar to those of cows that ovulate, but all of those follicles are gonna fail to ovulate.
So the two types of cysts that we get, we get follicular, which, which are estrogenically active, so producing oestrogen. Therefore, they are gonna lead to more, estrous type signs. So we see increased mounting behaviour, lymphomania, hyperestrogenization.
So, we may get swelling of the vulva, And, and other sort of development of sexual characteristics, but there'll also often be a decreased milk yield, whereas luteal cysts, . And what what are term progestogenically active follicular cysts. So these are follicular cysts that have got a slightly thicker lutealal tissue wall around them.
So those cows will typically be anestre, so they won't be showing any signs of heat, and when we look at the data, we'll see extended into estre intervals. So Why do we get these cysts? So the physiological cause is that we don't get an LH surge that triggers ovulation.
But again, as we've talked about with effects of fertility, there are lots of other factors that will predispose to cystic ovarian disease. And these will be metabolic disease, uterine disease, again, negative energy balance, or high productivity, previous dystopia, stress, but also genetics as well. So I suppose the, the simple answer is we don't 100% know why cysts develop, and I think it'll be difficult to identify an exact reason for every cow.
The other structure that we can get is a persistent corpus luteum, and these cows will often be observed not in heat as well, . And may be mistakenly considered as pregnant. So in a, in a beef system, if they're not coming back into Eastres, they're not gonna be mounted again by the bull.
So we might wrongly assume that they are, they are pregnant, . And what it basically means is while we have that persistent corpus luteum, we have active luteal tissue on the ovary, producing progesterone, leading to an an ovulatory state. So the growing follicles are gonna, they're gonna proceed to dominance, but they're not gonna ovulate.
And that's due to the, the negative feedback of progesterone on, on LH release. So lutolysis should occur around day 17 of physiologically just in the cow, and it's triggered by prostaglandins. So any corporal lutea that persists on the ovary beyond day 20 would be considered as persistent.
So if we're gonna turn these persistent CLs when we're doing our routine work, we really need to know exactly what's happened to that cow on what day and date so we can work out where they are. Because of the progesterone, they're not gonna, show signs of heat. So, you know, these are cows that might be presented to you as he's just not observed.
And yes, they're gonna pre prevent that LH surge leading to ovulation. Uterine infections post calving, can also disrupt the function of, the uterus ovaries, the hypothalamus, and the pituitary gland. So again, identifying diseased, uteruses early and, and getting, effective treatments on is really important.
So from this work by Sheldon and Dobson, 2004, they identified these factors contributing to uterine infections. So damage to the uterus, due to stillbirths, twins, dystopia, seizures, retained placenta, or if there was any delayed uterine involution. They also linked it to metabolic conditions, so milk fever, ketosis, left displaced Abermasin.
And that there is this balance between pathogenicity and immunity. So if there's been any disruption of neutrophil function or an increase or a disruption in the bacterial flora in the uterine lumen, remember that the uterus does have an, a normal bacterial floral population, . If there's been any progesterone or steroid administration.
And really importantly, the hygiene of the calving environment, you know, our external bacteria can overwhelm that delicate balance, inside the uterus if we're not careful. What can these infections lead to and why does it have an effect on fertility? So, not only can it decrease fertility, but it can be fatal to the cow.
So acute papura metritis, can have a high mortality, or it can lead to chronic infections, and therefore infertility. Endometritis, can lead to decreased fertility. Our luteolytic path will be affected, which means that you have a prolonged exposure of the uterus to progesterone, which has an immunosuppressive effect.
There can be decreased milk production and an effect on ovarian function, so again, a delay in first ovulation and sort of . Retarded retarding of the growth of the dominant follicles. So how do we treat lots of these conditions?
Again, we, we will use agents that replicate the actions of the hormones that we've already talked about. So, gonadotrophin releasing hormone, again, what I got here is the sort of the common products in the, in the UK, but they're basically used for the treatment of follicular cysts to help with ovulation, alongside AI to synchronise animals, and to treat, repeat breeders. Prostaglandins, these will sort of force or cause the functional regression of luteal tissue, so cloprostinol, dioprost, so again, they're used to, To promote cycling, to terminate pregnancies, to help treat, uterine infections, to treat luteal cysts.
And then our progestogen devices, these are intravaginal devices that are impregnated with progesterone. Two different types in the UK, Caesars and rids with different amounts of progesterone on. And again, they're used in various synchronisation programmes.
They're used to synchronise recipients and donors in ET programmes, and can be used for fixed time AI protocols. PMSG pregnant mare serum, gonadotrophin, so it's as a supplement or a substitute for LH and FSH, so it will stimulate development of the follicles. So it's used in east just control in non-cycling cattle and also in supovulation for embryo transfer work.
Then HCG or ECG, human or equine chorionic gonadotropin, basically, works the same as LH, so it can be used to promote the maturation of a, a, a follicle, an ovulation, and lead to that formation of a CL. So I don't think it's commonly used. I certainly don't use it commonly, but it can be used in those cows that repeatedly fail to conceive, or in cystic ovarian disease.
So where do they fit into our, our table that I showed earlier? So PMSG is replacing the FSH or the LH, and here I've put some of the trade names available in, in the UK. Corallo, which is the, chorionic gona gonadotrophin product.
And then our GNRH products, recepty ascigon overrein, our progesterone devices, and then our prostagland is down the bottom, estromate and the like. So to summarise that before we move on to our next section, the cycle is complex and there are lots of hormones involved, and they all have an interrelated effect on each other. And in balances, those hormones can have detrimental effects on fertility, and there are lots of products available for us to manipulate yeast just with.
So there are a large number of protocols described for manipulating e-stress, and lots of those will also help describe some of the reproductive diseases that we have mentioned. Pharmaceutical companies, when they describe their own, describe protocols, they tend to do them only using their own products, but they are, those products are interchangeable if they are, doing the same thing. And the prices of the protocols will vary depending on the location of the drug costs.
So it's always worth having an awareness of what some of these protocols cost because Actually, they're not cheap, and even injecting er cows with just GNRH can soon add up for farmers. So, I'll include these in, in sort of the notes that will be available, but there are lots of protocols, and they will rely on Ere detection AI which is represented by EDAI or fixed time AI, TI AI, . So we can just use prostaglandins to, you know, lies the CLs that are there, and if there is a dominant follicle, we will see east just after that.
So if you give two prostaglandins 14 days apart, you should be able to either serve them after the first injection or after the second. Excuse me. Or we can use the progesterone devices, with the prostaglandin at the time that the device is removed, and again, we should see heat within the 7 days after removal.
We can use GNRH at the beginning to stimulate follicle development and. Use prostaglandins again to lise any corpus lutea that are present to cause an LH surge to allow ovulation. And again you can add progesterone devices into that protocol as well.
You can do combinations of prostaglandins followed by gonadotrophin releasing hormone with progesterone devices, . But generally all of these protocols will involve a prostaglandin at some point. Some of these ones with time AI, so, you know, we start off with our GNRH product.
We then give a prostaglandin if we haven't served them. Then if we do see an estrous, we can serve them at that point. If not, 3, 3.5 days after we've given that prostate glandin injection, we can do time AI, and it's this protocol suggests giving a GNRH at the same time as U AI.
Again, different protocols around, . Note that this one doesn't have a GNRH at the start. This is a similar one, but with GNRH at the start to kick off those follicular waves.
And these with sort of double prostaglandin injections, . These are meant to er yield a greater number of pregnancies than say these protocols with the single prostaglandin. And there is some work that's looked at, we'll talk we'll mention the this protocol a bit later, but one where you don't use the progesterone device, so you're doing what what commonly we call an off sync programme, but repeating the prostaglandin 24 hours later and.
There is data out there that shows later lactation cows do respond better, so cows that have had more carbs, around sort of, if they're in their 2nd or 3rd lactation, will respond better to getting two injections of prostaglandin 24 hours apart. Again, these protocols, mixing, lots of different things, sort of, treating them before you put in the devices. This type of protocol is gonna be quite expensive, particularly if, if the vet's gonna have to go out and do all of these injections and insert the devices.
The idea with this is, if we see the animal come into heat in the 1st 3 days after the prostag glandin, they get served, but then a progesterone device is inserted in any that aren't served. Again, we can use time day I 10 to 12 days after the, the second prostaglandin, and that's gonna give us, better, fertility. So a double off sync programme, so we're, we're giving, GNRH followed by pro landing, but then a second GNRH and then we're gonna start a a time AI programme.
So these are all sort of precinct programmes. Again, of sync, with this one you can use a progesterone device as well, inserting it with the GNRH and pulling it out with the second prostaglandin. And again, another one just with slightly different timings at the end.
And again, these might all work depending on the management of, of the farm. So, not gonna go word for word through each of these. If we now move on to some of the examples from the pharmaceutical companies, these will all be similar to the ones we've talked about, but they may give you specifics about this one interestingly is, after a cow's calved, they just get a device put in at 50 days.
So we're basically getting them served as close to the end of their voluntary waiting period as possible. And then again, you know, lots of these are from Zoettes, so looking at where they might fit into different systems. So these ones for, for beef for the start of the breeding season, programmes that are suggested for animals that we know are cycling.
Device programmes for those that we know are cycling and whether they're through heat detection and AI or fixed time AI or natural mating. So again, there is lots of information out there, and it is well worth talking to the vets working for these pharmaceutical companies if you have farms with, with problems, to see what, what data you need to collect to identify what the problem is, but also what combinations of products might work best for the different, setups. When we look at the literature, so cows with cystic ovarian follicles have a good chance of conceiving when synchronisation programmes are used.
So, so don't, I think historically, people haven't wanted to serve cows once they've used sync programmes to treat a cyst. But actually, there's no reason from the literature not to, not to serve them. And whether that's with the progesterone devices or not.
This study looked at, giving GNRH sort of at the end of the, the sync programmes, and actually, they felt that maybe those programmes that had a second GNRH at the end produced weaker LH surges, and maybe did not get as as good an ovulation rate. This paper was looking at for embryo transfer and found that synchronisation of recipients, produced better outcomes. And this one looked at the 5 day versus 7 day cosync, and actually they found that they had very similar results.
So then we need to think about, you know, what, what, what is the effect on the farm. Well, actually, if you're doing a 5 day programme, there's potentially more labour, more labour involved, so actually it may. Be less welcoming on some farms.
And if we know that actually it doesn't have any better conception rates, then, then why not, just go with the 7 day. So there is lots of information out there, comparing different programmes and on different farms and again, you'll find that different pro protocols work better on different farms. To summarise that, there are a large number of protocols.
The pharmaceutical companies will provide you information, but the products can be used, from other companies within those protocols, . And the, the sheer variety of protocols enables you to match them to your farms. And we know that the protocols do work, .
But if you use them on a farm and they're not working how you'd expect, it will be worth looking at the other potential er contributing factors to infertility. OK, so what else can we do to improve fertility and repro performance? I think lots of farms are still selecting their breeding animals visually.
So those visual assessments will be based on the size of the animal and their appearance. And you can't evaluate reproductive traits by external visualisation. You know, we need to use estimated breeding values, we need to use res reproductive tract scoring, and we need to use genomics.
So what is repotre scoring and why should we use it? If we can identify heifers early, that are reproductively active and breed them successfully, then our early calving heifers will have a higher annual lifetime calf production, and therefore, milk production. So whether it's in a beef farm or a dairy, there are economic, benefits to having younger calving heifers.
And when we look at the age of puberty, it is associated, the lower the age of, the age of puberty is associated with the pregnancy rates, the percentage of calves, cows that calve in the 1st 25 days of the season, the milk production and progeny weaning rates. How do we do reproductive track scoring, so it is a . It is an ultra sonographic examination of the retract rectum, and we are looking to see what is happening with uterine horns and what is happening at the at the ovaries.
And the lower the score, the more immature the animal is. So we are looking for uteruses that are a good width, so 30 millimetres with good tone, and we are looking for decent follicles with or without corpus luteia present. Obviously if there are follicles and corpus lutea, we know that that animal is cycling.
So we're really aiming for, for fours and fives, when we're choosing, heifers to breed. So we're estimating that pubertal status, . And what the score, what scores you get will depend on when we examine the animals.
So. Heifers that are less than 12 months, the majority will not be cycling, so you will get those lower scores. But then if we assess them too late, we'll have more high scores, but if we're using reprotract scoring as a means to, to, to identify animals that we want to get rid of from the herd, that's not gonna help.
So most heifers are commonly assessed when they're 12 to 14 months of age, to really get into that correct time frame. And really doing it sort of a month before we want to, to serve them. If at that stage we find heifers with a score of 1, they're immature or infertile, with a score of 4, they're likely to be cycling within a few weeks, and those of a 5 are cycling at at the time.
And those scores are highly correlated with their reproductive performance, so the higher the score, the better their reproductive performance. So we can use it to select heifers that we want to cull, because we know that they're immature and therefore aren't gonna fit in with our breeding pattern. We can identify visuably suitable heifers, the ones that are not reproductively mature, so again, may not get in calf when we want them to.
And we can use it to identify any developmental deficiencies in a group. So, you know, maybe if, if all the cows are not, reproductively active, maybe it's something to do with how we've managed them. What do we do with the results?
Any heifers that score 3 at 30 days prior to breeding will have a 20% will have 20% more empty heifers than groups with scoring a 4 or 5. So, you know, that's a fairly significant chunk if you're breeding those animals with the scores of 30, and, and if the farm still wants to breed them, that's fine, but at least you know that actually that's the reason that 20% of that group didn't gain calf. And developing heifers on farms is a major expense.
So actually, if they do fail to conceive, that's quite costly for the farm, not in loss of loss of product, but also the, the cost of the semen or the sink programmes or, or all the other things that we're. Putting into them. What affects reprotract scoring, the age of the heifer, the cytogenetics, weight condition scoring, in breeding.
Other things that people will do with heifers will be pelvimetry. However, this is a directly related fertility. It will assess whether the the heifer will be prone to dystopia, which will then have a knock-on effect on subsequent fertility.
And here we're measuring, using a pelvimeter placed per rectum, we're gonna measure the width and the height of the pelvis to get pelvic area. So two different, this is the rice pelvimeter and then the crown bone pelvimeter. Moving on to embryo transfer, this is a quite effective way to improve the herd genetically, and do it faster, so we can get more cars from specific valuable cows.
We can therefore increase the rate of genetic improvement. Genetic improvement can be quite a slow process in a herd. It also will help us to more rapidly evaluate bus in AI centres.
It helps with disease safety. And We can see improvements in production efficiency, modification of milk, and improve resistance to disease by by selecting the better cows. There are two categories.
There's direct transfer of embryos from donor cows to synchronised recipients, or the transfer of embryos which have been preserved in low temperatures to synchronised recipients. And those embryos can be produced in vivo or in vitro. Embryo transfer has definitely increased in popularity and use, and it, as I mentioned, it's a really good way of improving genetics in a farm, particularly in the dairy industry, breeding programmes have been developed to promote genetic progress by use of elite females, through multiple ovulation embryo transfer programmes.
And these programmes er in most mammals include the administration of those drugs that we talked about, the superrovulate females. And in 2018, there was over 1.5 million bovine embryos collected from super ovulated cows worldwide, with 1 million of those produced via in vitro fertilisation procedures.
So, you know, significant numbers. It seems to have stabilised now, but there was certainly an increase up until sort of 2018. So we talked a bit there about genetic selection.
So, Fertility is gonna have a huge, huge impact on profitability, and we need to look at reproductive traits. Most reproductive traits they do have a low heritability. So potentially have less of an impact than good management and nutrition will have on a herd.
Heritability is the additive genetic variation of a trait, so the higher the heritability estimate, the higher the contribution of genetics to that phenotype. So some have good heritability, as we've said, reproductive traits are pretty poor, but other morphology is quite good. So we can use genetic selection to prevent disease and problems, we can use it to improve the economics of a herd.
We can have cumulative effects, and we can also have very long lasting effects. So I often talk to farmers about genetic selection by, you know, it's a long term goal. It's not what you want your herd to do in a year's time, it's what you want your herd to be in 5 years' time, 10 years' time.
And we need farmers to know what they want to do with their herds, they need to set a goal, keep accurate records and use established indexes. Some genes will correlate with other genes, so, there is a negative correlation between milk yield and fertility. So the better the milk yield, the poorer the fertility.
However, there's a favourable correlation between body condition score and, reproduction and an unfavourable correlation between BHBs and reproduction. So again, we can look at, if we're very much focused on one attribute, we may, have a detrimental effect on others. Genetics could be as simple as cross breeding and actually hybrid vigour can really help fertility in a farm.
So, you know, when we cross two or more breeds, and the benefit is based on how the genes for a trait will combine. And it will have a great impact on those low heritability genes, such as those for reproduction. So hybrid vigour, we have individual which affects the calf, we have maternal and we have paternal.
And each of those can have an overall effect on herd fertility. It can lead to improvements in live birth rates, and improvements in survival to weaning. When we're looking at the hybrid vigour in the calf, the dam, hybrid vigour can lead to improvements in conception rates, increased live birth rates, and improved survival to weaning.
However, with the bull, there is little known about the impact on, on, on of hybrid vigour on, on the bull, but it is likely to have a positive effect on the capacity to serve animals. Bullproofs may demonstrate a range of selection indices, so we do use, bullproofs quite a lot when choosing the sire, and it's important to understand what traits are included. Bullproofs will define the breeding values for a name sire, and estimated breeding values are the most common index used on bullproofs.
And those values can be positive, negative, or zero. And they indicate where that animal lies compared to the meat. So there are lots of selection indices out there.
The expected progeny differences are an evaluation of the animal's genetic worth as a parent, and it combines all the information learned about an individual and its relatives. They're then compared only to other individuals of the same breed. And currently some of those EPDs include stability, HEPA pregnancy rates, 13 month pregnancy rate, scrotal circumference.
And there are a number of reasons, you know, why we look at this. So stayability will predict the probability of the daughters delivering a calf each year. The pregnancy rates, er, the daughters getting in calf.
The daughters being calf, . And carving at 3 years of age, assuming they carved as a 2 year old. And as we know, scrotal circumference is not only related to improved fertility in the bull, but also in, in the daughters as well.
Profitable lifetime index is also used a lot and that's a within breed genetic ranking, particularly within the dairy industry. But the values from different breeds are not gonna be directly comparable. So if we look at this one, the pounds for PLI, this is, you know, the, the top 5 balls for non-hystein breeds.
And a lot of this data is available from, from, from the companies working with this. It's used commonly in all year round calving farms, as an as an initial screening tool in bull selection, and then they'll look at the specific traits to improve the herd. And PLI is made up of lots of different traits, which contribute to it.
For spring carving herds, there's a spring carving index for our beef farms. And this is used by spring block carving herds that rely or or our dairies relying on grazed grass, so again, choosing the best bulls and again used as an initial screening tool. Again, it's slightly weighted differently, and then autumn carving index does the same, but for our autumn block carving herds, who might be relying more on winter feeding.
And again, it's made up of different weighted traits. Fertility index is a combination of various measurable traits, . And it's been used to improve fertility in the UK.
And it's made up of 6 traits, carving into the non-return rate, body condition score, measure of milk yield around insemination, days from calving to first insemination, and the number of inseminations needed to get the cow and calf. So, if you were trying to improve the fertility fertility in your herd, this is an index you might consider. And again, it's on all these proofs that are out there.
Cause, total performance index is the most common index used in in the US, but it's not aimed at breeding individual cows, more looking at the herd. And again, lots of different traits are included in this. OK, so how do we predict these breeding values?
Well, firstly, they can be confounded by heritability, er, if we're comparing different groups, and the number and type of records we've got available. You'll all have seen EBVs, so I'm not going to spend a lot of time talking about these, but, you know, we can see, EBVs for carving ys, for gestation length, birth weights, the growth rate at 200 days, at 400 days, at 600 days. And again, depending on what your farm is aiming for, will mean that they want to look at some of these different traits.
Milk would be an important one, so for dams, it's gonna indicate the milking ability, but for sires, it's gonna, indicate the effect of the daughter's milking ability. And then scrotal size, as we've talked about, is a good er has a good correlation with fertility. Carcass weights will be important as will our muscle area for, for the beef guys.
Rib fat, rump fat, beef yields and intramuscular fat, again, all key EBVs that that most board proofs will talk about. OK OK, so we've talked mostly about that. EBVs are expressed in the units of measurement depending on the trait, and they're shown as positive or negative, between an individual animal and the base to which that animal is compared.
So, and a bull with an EBV of plus 25 kilogrammes, is estimated to have a genetic merit 25 kilogrammes above the breed base of 0 kilogrammes. So EBVs can be used as the basis for comparison of the genetic merit of animals and selecting the right animals for our breeding. And they provide an estimate of the animal's genetic merit for a range of production traits.
So we can use these in conjunction with visual assessment or other for other traits of importance, but EBVs are definitely a a good way to see what's gonna happen with the offspring. And one of the main advantages is we can avoid those extreme straits, traits and select animals that are a bit more balanced. So here's some examples of what a breed trait will look like.
To the right is easier or lighter or heavier, so please explain what what each means. Whereas these ones just kind of give you the, the figures, but again, to the right normally means they're positive, to the left means they're they're negative. We also need to think about accuracy.
And accuracy is based on the amount of performance information that we have for those animals. And we may find two balls that have exactly the same values, and then we may want to consider how accurate that value is because the higher the accuracy, the less likely that those figures will change over time as that bull has more offspring. So yeah, greater than 90% would be high accuracy, so it's, it's, it's a good estimate of the animal's true breeding valuables.
If we want to interpret our EBVs, we need to halve the bull's EBV to estimate how much genetic superiority is passed on to the progeny. So a bull with a 400 day weight EBV of + 40 will produce carbs 20 kilogrammes heavier at 400 days than a bull with an EBV of 0. So just flicking through these different ones that we have, negative values for birth weight will be lighter carbs at birth, negative values for gestation will be shorter gestation.
And then there are some breeding indexes where they combine EPVs, so a beef value will combine the EBVs birth weight, 200 day growth, 400 day growth, muscle depth, and fat depth. A maternal value. Or a calving value.
So again, these are easy ways of finding out, you know, which bulls might benefit, which packages might benefit your farms. So for this bull, you know, it's, it's, you probably wouldn't want to select this, it's, it's producing daughters with lower milk. It's got harder calvingieser and poorer muscle area.
This one has a smaller scrotal size, so again, fertility is gonna be worse. Again, calving ease is, is highly negative. This one's very poor calving traits and also poor fertility traits.
So moving on to genomic testing. Genetics, as we've said, are gonna play a fundamental role in herd health and profitability. And most genomic testing will look at these profitable lifetime indexes, .
So When we look at the farm performance, if we have . An animal with a PLI of + 814 is the best in a group, and the worst is -280. That means that the daughters of that animal are gonna provide a profitability of an extra 1,044 pounds across their lifetime.
And we can do that for all of the different, sort of components on these genetic testing. We've talked about accuracy, we've talked about, heritability. Well, reliability again is, is related to that.
It indicates how likely it is that the animal's proof, genetic proof will change as they have more offspring. Genomics relies on these predicted transmitting abilities, and they predict to what extent a trait will be passed on. And we will have animals that will not have enough offspring, so then parentage average PTAs are used.
So, if we have a bull with a PLI of 592 pounds and a reliability of 64%, and the dam has a PLI of 44 pounds, and a reliability of 59%, then the calf PLI is going to be 318 pounds, but it's only 31% reliable, so there is a good chance that that figure will change as that calf has more offspring. So, genomics is really useful to study and evaluate the genes that that help predict performance. And, you know, the bovine genome has got a lot of variation.
So we use single nucleotide polymorphisms or snips as the most common type of genetic variation. And each of those is a difference in a single DNA building block. How do we get a genomic index?
Firstly, I'll say there are lots of companies that are now offering this service. We work very closely with Zoettas using their clarified, and I've been very impressed with the, the data that we are getting from it. And basically, there is a sample, either hair, ear notch, nasal swab, DNA is extracted.
It's placed on a snip chip. There's a sequence of bases of red at different locations. A snip code's produced, that's sent to a genetic evaluation centre.
That's converted to a snip code from the snip code into a genetic index, and then we get these PTAs produced. And what we end up getting is a list of different groups and the animals and what their, the these herd genetic report summaries are. And what we find is if we look at the PLI prior to genomic testing, so it needs highlighted animals, 56 and 23, well after genomic testing, the reliability is 67 to 34.
So genomic testing does provide enhanced reliabilities. In in matching these traits. Doing this work also helps us benchmark our farms.
So this is one of our farms, in the top 5% for PLI, the profitability, index. However, we have scope to improve our milk, our milk solids, but we've also focused, have a good focus on non-production traits. So again, highlighting what we're good at, but also identifying areas that the herd could improve.
And you can also get these the young stocks of those not contributing to the milk yet. And this farm is in the top 15%. And it looks like there is less focus on milk production, but potentially more on lifespan and, or we could work more on the lifespan and the mastitis traits.
So why do we use genomics? Well, it can help us decide which animals we're gonna keep for breeding and which semen we're gonna put into those animals. So in this farm, the average PLI of the top 25% of cows is 350, which means that a third of the heifers have a lower profitability index than the top 25% of the cows.
So actually, We probably don't want to breed these bottom end heifers, you know, we, so our options for this farm would be to consider using sex semen, between the heifers and the superior young cows that have a profitability above 300. Or there is a new dairy wellness profit in index, so we could rank the heifers on that and deselect 15 to 20% of them, for beef semen or to sell them on, because a lot of these heifers will still have, will still have a good, phenotypic characteristics, they'll still be look like, you know, they'll be good breeding heifers, but for what we are trying to achieve in this herd, we have identified early that they aren't going to, to get the herd on that path. Lastly, and I realised that you've all been listening to me for a long time, but I, I also want to mention that we mustn't ever forget about the bull and.
I know we've talked a lot about AI and therefore, you know, the, the bull's available is kind of down to, you know, what, what we can get, but lots of beef farms and some dairies are still relying on bulls. So we do need to consider that bull, because that bull, when it's being used, is 50% of our herd genetics. Bull breeding sound exams are invaluable, because we need to know that the bull can do what it needs to do in a breeding season.
And a subfertile or infertile bull could have a catastrophic effect for a farm. And actually you might not know until 3 to 9 months later, which by then it, it's too late for that farm. So the idea of a BBSE is to detect the bulls whose fertility is suboptimal, and then we can avoid using them.
And we need to do it in a time where we have time to test them, maybe even retest them, and then get another bull in if we need to. So a fertile bull should get 90% of. Normal cycling disease-free females pregnant within 9 weeks, and 60% pregnant within the 1st 3 weeks of the breeding period.
So graphically, you know, we, if we talk about a, a, a good bull with a conception rate of 60% versus a bull with a conception rate of 40%. You know, we, we should be aiming to get the majority of these cows served in the 1st 9 weeks, and again, this is important for getting that compact breeding system season that we talked about. And we mentioned this, that that will lead us to a homogeneous group to sell.
It'll be easier to manage, it's easier for disease control, it's easy for nutrition, but it's also, you know, I think, better for the farmer that they don't have a calving season that goes on and on and on. There were 4 stages. Most people will only do the 1st 3.
So with general, where we're looking at condition scores, confirmation eyes, teeth and jaw, reprotract, looking at the scrotal circumference, testicles, accessory sex glands, prep use and penis. Then we're gonna do our semen evaluation, and then you can do mating ability as well. A general exam, eyes, mouth, jaw, you know, is, are there any obvious defects that are gonna affect that ball long term or, or be passed on to its offspring?
What's its confirmation like, what's his body condition score like, and then has he got any heart or lung issues? Our rero exam, we're gonna do a scrotus circumference, we've talked about how this is highly correlated to sperm output, and fertility. And again, there are standards that we work towards, and some breed societies will have variations of that table above.
We're gonna feel the testicles for consistency, for symmetry, for mobility, and we're gonna palpate the epididymi epididymi as well, to ensure that there are no problems there. Per rectum, we're gonna palpate the accessory sex glands, the bulbary urethral gland, the prostate, the seminal vesicles, and the ampulla, and that can help us to identify any, any problems there too. Make sure there's nothing wrong with the prep use in the penis.
And then once we've got our, we're gonna think, once we've done that exam, we're gonna think about evaluating the semen and we collect this in a variety of ways. Electroejaculation is by far the most common, but it can be done by artificial vaginas or transrectal massage. What are we looking for on these semen samples, we want a good volume, we want a good colour and a good consistency.
So the creamier and the thicker it is, the higher density the sperm's gonna be. We can look at gross motility, making sure that the, the semen and the slide is kept warm at all stages. We wanna make sure that we get a good swirling motion, on, on our slide, and we really want it to be a 4 or a 5 on this scale.
Progressive motility, how many are swimming forwards, and we're aiming for more than 60% of sperm on a slide going forwards. So if we've got a very dense sample, we can dilute it with phosphate buffer saline. At the times 40 objective, with phase contrast or dark field, we can, and we should look at multiple fields.
If, the sample is poor, it's, it's worth retesting, and retesting on the day, just in case we've got a stale sample of sperm that was just sitting in the tract. Then we're gonna need to look at morphology, so we're gonna put one drop of semen and 2 drops of stain, on a slide and assess more than 100 sperm using all immersion. Alternatively, you can, sort of kill the sperm with formal saline, do a wet mount, and then look at that under phase microscopy or immersion.
The target for morphology is greater than 70% normal sperm, and some of the abnormalities you might see would be proximal droplets, distal droplets, distal mid-piece reflexes, cord tails or dag defects. For any of you who are interested in doing bull fertility, I would recommend the, the BCVA courses, they're a really good intro into how to perform these and give you the practical opportunities to, to observe. These tests being done, but also to look at, Semen and evaluate it yourselves.
So the fourth area would be mating ability. This isn't often, looked at by vets that are breeding soundness. But libido of bulls can be affected by their hormones, by nutrition, by their age, by their breed.
It is a heritable characteristic, but also if they're overworked. And actually, even if they want to mount, can they mount? So that could be affected by their back, their legs and feet, neurological conditions, maybe they've got poor confirmation.
Maybe they have some form of psychological inhibition. You know, maybe a farmer has hit them around the head a few too many times when they've been mounting cows, and now it's associating that behaviour with, with, with painful stimuli. When you're watching a bull mount as well, we need to make sure that they are entering the cow properly, and that can be prevented by a disproportionate in size or confirmation of the partners, but also anatomical defects in the bull or the penis.
So I realised that's been a lot of information, sort of thrown at you, but I, I hope that it's sort of highlighted the different areas that we can. Look at to improve reproduction and improve fertility on different types of, of farms. And, and I hope that what you go away with is, no matter what problems you've seen on a farm, no matter what farm you think you don't know what to do with, there is a solution out there.
And there are people out there within repro companies or within the drug companies who will lend you support and expertise to get to the bottom and, and, and arrange the best options for your farms. . I'll be happy to receive any questions by email through through the guys at the webinar vet and just like to say thank you for your attention.