Explaining Seasonal Breeding in Sheep with Emeritus Professor David Notter

Dr David Notter spent 25 years looking into the seasonality of breeding sheep and how to reduce it via genetic selection. We are very lucky to have him as a guest on the podcast today to share his wisdom on all things sheep breeding.

In 1977, the American Sheep Industry Association identified a pressing challenge: reducing seasonality in ewe breeding. Virginia Tech became the base for this research, where they aimed to create a flock of sheep capable of breeding throughout the year.

They assembled a crossbred population consisting of half-Dorset, a quarter Rambouillet and a quarter Finn sheep. Initially, the ewes in the population had a pregnancy rate of about 50% during May and June (out of season for the northern hemisphere). While not an ideal figure, it was a starting point; within five years, the flock had reached 85%. By the end of the project, these ewes were breeding as successfully in summer as those being bred in the autumn.

One fascinating aspect of the study was the role of the 'ram effect'. Although initially expected to play a significant role in the success of the project, it turned out to have less influence than anticipated. Rather, the ewes themselves had an influence, explains David. “Just like you get a ram effect, you can also get a ewe effect by cohabiting. If you want to try and breed a bunch of blackface sheep, I would put them with a bunch of cycling Merinos or Dorsets, if you had them. We know it made a difference.”

Towards the end of the project, after years of selection pressure, some ewes had exceptional reproductive capacity. “These ewes successfully lambed around the shortest day and, approximately 60 days later, conceived during lactation,” explains David. He also explains that during the first few years, this wasn’t always the case with ewes absorbing the fetus far more regularly.

They also had issues with out-of-season lambs being slower to grow, which David believes is due to less-than-optimum uterine conditions during gestation.

David’s experience in this field is second to none and the wealth of knowledge in this podcast is phenomenal. Whether you’re contemplating out-of-season breeding, or you just want to know more about the oestrus cycle of your sheep, this podcast is not one to miss.

Head Shepherd is brought to you by neXtgen Agri International Limited, we help livestock farmers get the most out of the genetics they farm with. Get in touch with us if you would like to hear more about how we can help you do what you do best - info@nextgenagri.com.

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Transcript

Mark: 0:05

Welcome to the Head Shepherd podcast. I'm your host, mark Ferguson, ceo at Next Gen Agri International, where we help livestock managers to get the best out of their stock. I want to take this opportunity to thank our friends at MSD Animal Health in Orflex for sponsoring Head Shepherd again this season, and I'm also excited to introduce our mates at Heinegger as brand new sponsors of the show. Msd in Orflex, or perhaps better known as Cooper's Animal Health in Australia, offer one of New Zealand, australia's, largest livestock product portfolios, with a comprehensive suite of animal health and management products connected through identification, traceability and monitoring solutions. Like us, they see how the wealth and breadth of information born out of this podcast can help their men and their farming clients achieve their mission of the science of healthier animals. Heinegger will need a little introduction to our audience. A market leader and one-stop shop for wool harvesting and animal fibre removal, together with an expanding range of agricultural products and inputs, the Heinegger name is synonymous with quality, reliability and precision. The Heinegger team have a deep understanding of livestock agriculture, backed by Swiss engineering and a family business dedicated to manufacturing the best. It's fantastic to have both of these sponsors supporting us and bringing Head Shepherd to you each week and now it's time to get on with this week's episode.

Mark: 1:16

Welcome back to Head Shepherd. Awesome this week to be heading to the US, and we welcome Amaritis Professor David Noddard, to the show. Welcome, david. Thank you, mark, I'm a big fan of yours. You're obviously a long-term geneticist in the US, working there at Virginia Tech in animal science. I guess maybe we just start off with a bit about your career and then we'll get into some of the details of some of the work that some of the projects you've worked on or some of the traits you've worked on.

David Notter: 1:44

Yeah, well, I spent essentially my whole career at Virginia Tech working starting with beef cattle and sheep and just gravitating more and more to sheep. I kind of grew up with beef cattle and tobacco and thought I wanted to be a beef cattle geneticist and at sort of every turn I got shunted into doing something with sheep. I think that was the only species we didn't have on the farm where I grew up all I'd sheep and goats and finally just decided to give it up and bail all the way in. There's so much interesting biology with working with sheep, with seasonal breeding, parasite resistance, optimum litter size, just lots of fun things, and so about halfway through my career I said, well you know, just give it up and commit, and I've never regretted that decision.

Mark: 2:35

Excellent. Yeah, obviously sheep aren't anywhere near the scale in the US, as what beef is? Most people will be working in beef, so yeah, they'll be definitely compete, I guess different to where I'm today in Australia and where I am normally in New Zealand, where sheep compete pretty well with beef. So yeah, it's definitely very different in the US.

David Notter: 2:55

Well, I really wanted to work with producers and work with things that were going to be useful in the field, as well as the biology, though, so it was a great combination. Yeah, I actually took early retirement around 2010, when I was 60, and spent about a decade working with various projects in various places and really enjoyed that. Covid sort of said ah, maybe it's time to quit, so I've cut back pretty well in the last two or three years.

Mark: 3:23

Yeah, right. So maybe just for us who don't know the US very well, can you just explain to us, I guess, the agriculture around your region there and yeah, the sort of normal farms and what that's all you're trying to say.

David Notter: 3:37

Yeah, virginia is a fairly diverse state. I mean it runs from the East Coast. Fortunately we're about 200 miles from Washington DC, which is far enough where you can pretend it isn't there, which is a big plus. It's diverse, it's sort of mountain valley country Lots of grazing, lots of fruit, then, as you go to the coast, soybeans and tobacco and leave it, cotton again, which has sort of made a resurrection in the state. So it's a nice small town we're sitting about in terms of latitude, which, in terms of some of the breeding season work I've done, becomes important we're sort of right between Hamilton and Auckland in terms of latitude. So yeah, I went to Virginia Tech right out of graduate school, but five years at US Meat Animal Research Center doing PhD work and then got to Virginia. I'm Ohio native, so moved around a bit.

Mark: 4:45

Excellent. So if we do get into that breeding season control, which is always pretty interesting, we're sort of kind of run on the theory. If they got black feet in the quiet seasonal in this country, but yeah, yeah, but, or bucks again like pigmentation and black feet. But yeah, as with everything, as I always say, everything down to eyelash length in a sheep is heritable, so it can change things. So I guess we interested to see what you studied and how heritable it was and how much you could shift it.

David Notter: 5:17

Well, I went to Virginia Tech in 1977 and one of the priorities from the American Sheep Industry Association at the time was to reduce seasonality of breeding. I had the potential to put together a reasonably sized flock of sheep there and so decided that was where we were going to focus. That turned into about 25 years of selection to reduce seasonality, which I would never have really guessed at the time. But we started putting together a crossbred population that was a half dorset, a quarter rambolet and a quarter fin sheep and we sort of felt like that bracketed what was the available breeding season at the time. Fin sheep did pretty well in the spring, rambolets did very well with Ram Effect in the late summer and dorsets were sort of the classic out of season breeder for us. And the population we put together was about had a pregnancy rate in May and June a northern May and June of about 50%, so not really very good, but not zero. And so we had something to work with and over the course of the project, by simply identifying use that would mate and conceive in May and June, we were able to move to about 85% pregnancy rates and at the end of the project we had use that were breeding just like normal fall breeding use. We made one mistake. We should have picked a breed that we were going to focus on rather than building our own composite line. It was the right genetics to create the line, but it was the wrong genetics to have an industry impact, so it became too much of an academic exercise. But I think it kind of clearly said that we can, as you said, if you can measure it and it has any genetic variation at all, we can improve it and indeed we were able to do that. It was interesting.

David Notter: 7:36

We expected the ram effect to have a big impact on our success, although we did choose to breed in the spring rather than late summer when we knew the ram effect would have a big impact on our success. But in fact it had very little to do with the selection line. We basically just extended the breeding season through May and June and eventually at the end of the day we had used that were going antestrus for only about 30 days in late July and early August. So in late summer, maybe a month after the longest day, they were going antestrus for a little while and then starting up again promptly in early September, so early fall. So I really think we could have bred those sheep any time of the year.

David Notter: 8:31

We used ram effect for about five years of the 20 years and discovered that it really wasn't having an impact. The ewes were lambing heavily within the first 17 days of the lambing season, so they were cycling when the rams went in. It wasn't a matter of the ram effect doing it, they just extended the breeding season. We reached the point where we'd have maybe 15 or 20% of the ewes and some extensive studies. That never went antestrus, but most of them, even at the end of the day they needed a break. They needed one or two cycles and they would shut down for one or two cycles and then start right back up. So you can do it.

David Notter: 9:17

The question just became how does an industry do it? Well, you really need something like a group breeding scheme where you've got a selection nucleus that is floating out replacement ew lambs to a bigger commercial endeavor. And that was tough in the United States to do because we don't have very many of those sorts of true big nucleus breeding schemes. But it was fun. One of the more interesting things about it we found that those ewes we got curious near the end of the project we found that those ewes were very successful at lambing around the shortest day, 60 days later, conceiving while lactating in a lengthening day, and it didn't seem to matter to them at all, which surprised me.

David Notter: 10:11

So I would assume they would work very well on accelerated lambing as well. So it was a great study just trying to figure out clock genes and melatonin and what's driving this thing and what's not driving it was great fun. As I look back, it may be there aren't going to be very many long-term selection projects around anymore. They are out of vogue and nobody wants to pay money. But I had sympathetic administrators and sheep we used for teaching heavily, so had to do something with them and I made that argument several times to various administrators, but always successfully.

Mark: 10:54

Yeah, and I think it's very true. We won't get to see those long-term experiments or selection experiments well, ever a long time, but it feels like that those days are over. I missed a bit of that because the internet was being annoying. But what was the selection process? How did you? How was it just those that lambed earlier? You would just pick them and yeah, we basically just had.

David Notter: 11:18

We had a selection line that we put there, that we joined the use and rams in 1st of May, so 1st of November, in Southern Hemisphere breeding scheme. For the first five years or so we used ram effect. We primed them with vasectomized rams. Then we said, well, this isn't necessary, and it turned out it wasn't necessary. So we basically just kept the progeny of those use that could cycle and were cycling in May and June. We did quite a lot of ram serving capacity. We found out that if we were going to turn generations quickly we did have to be sure those seven, eight month old ram lambs were ready to work and about 25% of them wouldn't at that age, but enough would that. We were able to do that and, as I said, after about five years we took away the ram effect, just joined them without any priming. That worked well.

David Notter: 12:22

The biggest trick was getting a control line to see what had really happened, because if they lamb in the spring they aren't an unselected control, they're necessary. Sorry, if they can subbreed in the spring, they're not an unselected control. So we would have a spring lambing flock and we moved those U-lams to the fall lambing system and they were our controls and interestingly they did improve as well. And I think they improved because they were being bred with a bunch of cycling use. So just like you get a ram effect, you can also get a U effect by cohabiting. So you know, try, if you want to try and breed a bunch of blackface sheep, I would sure put them with a bunch of cycling marinos or dorsets or something, if you had them, and I think it would make a difference. In fact we know it made a difference. We did a couple experiments with Hampshire's and if you cohabit them with these out-of-season breeding sheep they do a little better. They don't do much, but they do a little better.

Mark: 13:29

So even in marinos, you still get a while, though we'll breed much. Yes the time, but you still get an impact. Like, as you get closer to the shortest day, the ovulation rate increases. Did your selection lines See that's going to disappear as well? Like did the? Did I get less responsive today? Length overall.

David Notter: 13:48

We we did early on the litter size responded with the selection for out of season breeding. So these were sheep that had a oh, they had probably a what two, two, twenty to thirty percent lamb drop Litter size born per you lambing and that went up for about five or six years and then it flattened off. So it looked like we got a little bit of benefit from that out of season breeding on on litter, on lamb drop, and then it kind of flattened off and they became very much like a spring lambing flock. But but yeah, we, the biggest trick was we, we, the thing we really coveted. We got a Eight month old you lamb who would conceive in May and June and there were not very many of those but they became the mothers of stud rams really, really quickly.

David Notter: 14:45

Yeah, it was interesting, by the end of the study those seven and eight month you lambs Sort of broke through all through. I 80% of the study those were 10% pregnancy rate sheep in May and June and the last four or five years they went up to about 30% there. So we were breaking through. You know, the adult use were pretty good and got better. The two-year-olds kind of took a few years and they broke through and got better. That the very end the you lambs, the hoggits, were Breaking through and getting better. So it was an interesting sort of step-wise response.

Mark: 15:30

Yeah, it is.

David Notter: 15:32

But I think we had, we had pushed it about as far as we could when we, when we tried to breed these Lactating use. A lot of them would breed back in the spring and summer. But we found we really had problems with those animals maintaining pregnancy. They just didn't seem to have the uterine capacity or the cl Well, prolactin levels that really let them set into a good, strong pregnancy. And we were pushed them hard enough. They would still cycle, they would still mate, they would still get pregnant, but they had trouble getting those pregnancies to term. So there are limits still and what we could ask these guys girls to do.

Mark: 16:11

Yeah, was there any Like in terms of either fanatical genetic correlations, like if we ran these two groups of years, your controls and your Out of season selected you used? Is there anything you could tell the difference Like to to that, other than if you put the ram in and find out? Is there any fans of it?

David Notter: 16:29

No, not much. They were. They. No, they weren't very different. Really they didn't change much in growth. They were not. I Think you would see some early and maturity at a phenotypic level in the selected line. They certainly, and we tried actually to convince some of our polyprey breeders, which is a Composite line that is very like this selection line, but they just weren't willing. They wanted something that was bigger and prettier. So they they stayed right where they were over those years in body size and all of that type frame score, whatever you want to measure, but there was nothing much else. Squirrels or conference went up a little bit in the selected line, especially around 90 days around puberty, so they were a bit earlier maturing but nothing else really Striking. They were just a medium-framed white-faced sheep.

Mark: 17:26

Yeah, did you ever do any work on gestation length?

David Notter: 17:31

No, we did not. We did see some evidence that that fall Born lambs fall born lambs had a much bigger maternal impact on birth weight, though in terms of a heritability, the piece of birth weight that was controlled by the genotype of the dam or the sire of the you was considerably bigger. In fall lambs were three, four-tenths of a kilo lighter in fall, just phenotypically lighter. So apparently we kind of thought it was. You know they were gestating through the summer but it wasn't really the time when you'd expect heat stress and we don't get much heat stress we're at 800 meters so we don't get a lot of heat stress.

David Notter: 18:26

But we did see some birth weight issues that we had to get through and I think what happened is we had used that would not have Conceived, that did conceive but still had something of an inadequate cl, an inadequate Implantation, and we got some small, light lambs. We put a little bit of pressure on maternal birth weight effects in selection but really after about five or six years it worked itself out and that problem largely went away. But early on I think there's some use that just would never have conceived without being pushed genetically to do so. So early on there were some problems with smallish, weakish lambs, but they worked themselves out and I lay it to the use becoming more adapted to that season of lambing. Whether that's really true or not, I can't prove so the heritability of maternal birth weight.

Mark: 19:23

It was high. In what Fall? When they land in the fall or land in the spring, land in the fall?

David Notter: 19:30

Yeah which yeah, use it had gestated, that conceived out of season, gestated through the summer, and I think that was again an effect of of whether they were able to put together a you, a conceptus package that was going to really do well. Yeah, right, I interesting and we had a student several years back who compared our control lines and our selected lines. Before they weren't really very different and there was a considerable difference in the magnitude of the maternal component. So just one of those intriguing things that pops out.

Mark: 20:09

We spend the rest of their laughter on the stand, which is always good you know, even we even spent a little bit of time.

David Notter: 20:14

One of One of your colleagues at Trisha Johnson even spent a few months with us when she was interested in Out of season breeding, right after finishing her PhD.

Mark: 20:27

I'm sure Trisha listened along, but yeah, she's now a working in methane mainly.

David Notter: 20:31

But I know, yeah, everyone moves to, everyone moves to genomics now for, yeah, they sell out. Yeah, it seems to be the driving force and keeping it, keeping it really useful and linking it to the performance recording is an interesting challenge. Yeah, we spent. I spent well ten years doing the EBVs for the for the US sheep industry and Was wise enough to get out of that before we had to start working with genomic EBVs and Convincing breeders just a bit d&a and figuring out what to do with it. I left that to my younger colleagues.

Mark: 21:05

Yeah, certainly an interesting time. And now the power week now wield is it's giving it better tool. It's all zero without the phenotypes. So we still need to stand here to keep doing the hard yards.

David Notter: 21:18

Indeed, it is, that's right. Well, I had an interesting conversation with a group of breeders here, our cataritan breeders, which is a hair sheep composite line, who are very, very keen to get genomic EBVs and moving that direction, making a pretty good commitment. And as I was getting ready to talk to them I kind of remembered some of the things from our out of season work and some of the things from our early parasite resistance work that when you collect the phenotypes you pay attention and when you pay attention you learn things and you learn management things and things you want to do that you could do better. When you go oh gee, I just should send in some DNA and see which of these is the one I want you don't have to pay attention. And the phenotyping and the paying attention has a lot to do with making genetic improvement or at least making improvements in a flock.

David Notter: 22:17

We had a set of Cotodin breeders who decided they were going to breed for parasite resistance. Small flocks, heavy challenges, but small flocks. They measured fecal egg counts on everything every chance they got. They learned a tremendous amount about parasite resistance in their sheep and they really set the stage for us to get engaged with that breed in doing proper EBVs for fecal egg counts and parasite resistance. Those breeders and the people who worked with them are now reaping pretty good benefits from being able to market documentable parasite resistance sheep.

Mark: 23:07

A quick interruption here to remind you of Hedgehip at Premium and our consulting services at Next in Agri International. If you love this podcast and want to hear more of them, visit the hubnextinagricom and sign up for Hedgehip at Premium and get an extra podcast each week. If you're listening to this and thinking you really do want to maximise the genetic gain of your livestock and feel more confident around the decisions you're making on farm, then send me an email at mark at nextinagricom and we'll get in touch and see where that takes us. Yeah, that's a great segue to move into parasite resistance and just to reiterate what you said before, I think you do.

Mark: 23:44

As I've stated before in its Jane Rives quote, if you measure it at moves and that's the beauty about taking those phenotypes is being connected to your sheep in a really intense way and there is a lot of power in that. If we move into parasite resistance, as far as I'm aware from my small interactions with a few breeders in the US via this podcast is that you're not blessed with quite as many registered chemicals for parasites, so maybe it's even more important in the US than it is in New Zealand, australia, although it's very important here now with resistance of the parasite to the chemicals and just, I guess, market resistance to chemicals in general, and then the capsules that we've been able to use to get us out of jail a few times have also disappeared off the market. So, all of a sudden, genetics around parasite resistance are root.

David Notter: 24:35

Oh.

Mark: 24:36

I didn't know that All these things are becoming all that work is becoming really important. So it'd be good just to, I guess, understand about the work that you did and what you found, and also if you could just make a comment on resistance versus resilience, which is a discussion we end up in a fair bit, and myself I'm a fan of where we make selection and selecting for resistance, but if you, I guess deciphering the difference between resilience and resistance is important as well.

David Notter: 25:06

Well, we were fortunate we had some breeders around us who did have some of the Caribbean hair sheep breeds St Croix or Virgin Islands White, blabratus, blackbelly breeds that had arrived in the US from West Africa or arrived in the Caribbean and then on to the US and West Africa. And we also had this breed, the Catahden, which is something like half Caribbean hair sheep, half blackface local sheep, with a little bit of Wiltshire horn kicked in for fun, which we knew had some level of parasite resistance. And so we originally started out working with the St Croix, the Virgin Islands White, to see, well, just how resistant are these things? And the answer to that was they are very resistant compared to anything we had. And so we began looking at that, trying to understand that resistance. And you know there have been tremendous efforts all around the world to figure out where are the genetics, what are the genes that allow these animals to be parasite resistant, and those studies have not really been very successful or they certainly haven't been consistent from country to country and breed to breed.

David Notter: 26:28

So we did several intensive studies with hair sheep and hair sheep crosses to say, well, you know what happens when you give them a parasite challenge and you know, to put it in my preferred technical term, when you challenge them with parasites the whole immune system lights up like a Christmas tree. It just all the immune effectors are thrown into gear, the one that I was most surprised about. We killed some animals and collected in abomasal epithelium and looked at you know some of the genes that were being expressed there. But when we did that we found that the lymph nodes in those hair sheep under a standard parasite challenge were something like four times the weight of the lymph nodes from comparable and larger wool sheep and the response of the lymph node to infection in the wool sheep was minimal. The total weight of abomasal or GI lymph nodes in the hair sheep went up almost ten fold when they well, no, sorry, went up about four fold when they were exposed to a parasite challenge. So the immune system was ready to go and just exploded when they got that parasite challenge.

David Notter: 27:59

So from there we went to the cattodon breed. The breeders were already interested. It's about 50% hair sheep, 50% wool sheep and we're able to leverage that to get EBVs for parasite or for fecal egg counts in the cattodon breed and the breeders who did that have been very successful. The cattodon we've got. If you look at the southeastern United States, it is a really good forage environment and is also parasite heaven hot, rainy, just not. Anywhere. You found a traditional wool sheep and these cattodon crossbreeds are quite popular there and function there very nicely. So that's been. One of our most active interactions with the industry was getting these cattodon sheep and an EBV for parasite resistance and working with people like Daniel Brown in Australia and others to figure out how to do that well and it's been.

Mark: 29:07

It's paid off tremendously for those cattodon breeders in the southeastern US so I guess on the ground, what that looks like is, yeah, a manageable situation versus a completely unmanageable situation if you've got genetics that can fight the worms themselves rather than you're trying to fight it for them. It's completely changes, I guess.

David Notter: 29:32

Yeah, I mean we have the same problems everyone else does with parasite resistance.

Mark: 29:36

Yeah, and I guess often we see genetics as sort of cumulative and slow, but things like parasite resistance just sort of get to a bit of a breakthrough where all of a sudden the sheep start winning the war and then start reducing the lava load around and then sort of it snobles in the right way rather than the wrong way all of a sudden.

David Notter: 30:00

Exactly. Well, I like to look at it and I tell our breeders that you can breed a sheep that is going to be forgiving. You probably can't breed a sheep that is absolutely parasite, resistant, resilient, whatever term you want to use but you can breed a sheep that's forgiving. If you make a mistake, or you're two weeks late getting the sheep dewormed or the first dewormer doesn't work, they're not going to die. They're going to continue to function, continue to grow a little and then you can kick your management in and solve the rest of the problems as necessary.

David Notter: 30:38

This concept of resistance, resilience I'm quite confident that what we were selecting for in the Katahdin was a resistance phenomenon. They didn't have worms there. They were able to prevent a really heavy worm load from establishing in the abomasum. Several cases where we got basically a very clear self-cure phenomenon a sheep that had quite a few worms and then got a big challenge artificial or natural would just go to zero fecal egg counts. They were able to just blow those sheep out of the gut or those worms out of the gut. We did a little work with Dorpers who I think are more a resilient breed. They aren't particularly resistant. They can die if they are heavily challenged. But they're tough. They can handle a pretty heavy worm burden compared to traditional wool sheep and get along for a while, but they'll push over the edge far faster than the Caribbean sheep will push over the edge. There is a difference in a resistance, resilience setting.

Mark: 32:02

One of the challenges as you move to resistance and often people use one outside side. That's really good breeding base for resistance and often they might not grow as well one of the challenges is that when you drop a resistant animal into an otherwise susceptible flock, they do a lot of the hard yards for everybody. They're fighting everyone else's worms. There's been work in WA that Yohann Grief showed and others that when you put a fence up between those, they actually perform really well because they control their own worms and they have control their own destiny a bit. One thing breeders have to be aware of as you go on the journey.

Mark: 32:39

You have to be careful that if you're mixing them with less resistant others, then they will be doing that. They're firing up. That immune system to that extent is energetically costly, so it's not free and it will impact other things in the sheep.

David Notter: 32:57

Indeed, and I think that was the beauty of some of the Caribbean hair sheep is they were never able to be selected for large body size, high levels of performance. They had to keep that innate parasite resistance they came out of Africa with, and they largely did so. You do have to recognize that they're not going to compete with American Suffolk or even a good dorset in terms of growth rate, potential leanness. They're going to just stay alive and function on a forage based diet and do well. So if you like that, it's fine.

David Notter: 33:43

But I think some of that example of the lymph node sizes and some of these things that was what they were there to do was they couldn't afford to not invest that energy in being parasite resistant. And we see several of our breeds now through our National Sheep Improvement Program recording fecal egg counts. But you come up with some real challenges, as you've just said, in figuring out how to get that implemented quickly. So Katahdin has had a. They've really had a leadership role and it's been good for them because it's given them an identity, it's given them something to work with as a group. So it's been good.

Mark: 34:31

Yeah, excellent. Yeah, no, certainly. And yeah, I guess I guess, as we time goes on and you get Now with breeding bays for all these things, you can find the sheep that have the growth and have the worm resistance and, like it's building this combination animals. Obviously it might not be as amazing at resistance as a cataract and whatever, but they, but we are. That's the duty. The beauty of quantitative genetics is you can kind of combine traits in a way that they don't know. Yeah but I'm naturally occur.

David Notter: 34:58

That's right. Well, it's interesting with our katarans. I mean, we, we see a, we see competition with maternal excellence and fecal egg counts. You know use that have really good milk production, really good reproductive potential. They suffer a little bit because they put themselves in a position Both as you and then their progeny, in the same position that you know, if your nursing are trying to keep, raise three lambs and keep them from getting eaten up by parasites at the same time.

David Notter: 35:30

It's tough, it's not something that's easy to do. So we have. We have manageable antagonisms, which is the beauty of of genetic evaluation systems. There they be, they move from being antagonisms. What can we do To manageable antagonisms where we can say, well, yeah, if you want a really, really prolific you, she's not going to be as parasite resistant, or her lambs are not going to be as parasite resistant as as a you that's having mostly singles and twins, and that's just. I don't know if that's genetics or just the inevitability of trying to partition nutrients. I think it's more of the latter. It's pretty tough to suckle triplets and keep them from getting wormy at the same time.

Mark: 36:18

Yeah, I think in a Intensive farming situation where you can control all the nutrition and control the environment, you can do amazing things. But in our pastoral systems, where you you're out there, out there, eating forage and taking on, Love at the time it's. It's a tough combination of things to do.

David Notter: 36:37

It is, but it's been great fun to work with. I mean, we've done a number of things with Mechanisms. I was blessed with a few students who had the skills to really look at Immunofactors and this sort of thing and, as I said, it's just, they just light up the whole immune system. It's quite, quite fun to watch those differences among the the hair sheep and I'm very, very cool.

Mark: 37:01

They're not.

David Notter: 37:03

Well, and Katahdin was worked out to be a nice balance. I mean, the the st Croix hair sheep is not really very much you want to have around. I always kind of liked them. I could put one in the freezer and the whole loin made a nice meal. But that's about the size of it.

Mark: 37:17

Excellent, yeah, no, we well, we might leave it there because I'm sitting in a hot car in in Australia, but Fair enough yeah.

Mark: 37:23

Yeah, we might move on, but, yeah, really appreciate your time and, and, yeah, your career and it's been great to get a few insights into into that time and it is awesome to to To all to have that time to over those years to really do genetic work. It's a it is a bit of a slow game, but that's such a powerful game as well and now we have Brings across the globe really using those tools the best.

David Notter: 37:48

Well, it was interesting. I spent a. I spent a year in New South Wales in this, in doing a sabbatical leave and met some of the folks who now we've Began to work with more seriously Daniel Brown and others and I was working with cattle at the time, but that was before I made the big switch. But that was still a, a really good experience to get into the southern hemisphere. Never made it to New Zealand, but I spent some time in Australia and with folks who've gone back and forth a great deal.

Mark: 38:18

Yeah, it's. Uh, well, we're very glad you did make that, make that shift to the, to the sheep industry, and uh, yeah, and yeah what, you're welcome in New Zealand anytime and that, um, maybe it's a more similar environment than Australia, a few mountains and a bit of elevation compared to most of Australia, but Indeed, I think it would be.

David Notter: 38:38

Yeah, yeah, yeah, pleasure mark. Thanks, david.

Mark: 38:41

Cheers. Thanks again to our mates in Hanega who are proud world leaders in the manufacturing and supply professional sheep shearing and clipping equipment. I understand that their customers rely on the quality and performance of their products each and every day. Also, thanks to our friends at MSD animal health and Orflix, the Alphan extension of livestock product portfolio focus on animal health and management, all backed up by exceptional service. Both of these companies are wonderful supporters of the Australian and New Zealand livestock industries and we thank them for sponsoring the HIPAA podcast.