Breeding Merinos that stand up to footrot

Why footrot took me to New Zealand

Now to the feet, which is way more exciting than artificial intelligence. The reason I defected across the ditch to New Zealand was footrot. It doesn't take much to convince me to leave the country, obviously. I went to work for a company called The New Zealand Merino Company, and we've got representatives of them here today in Emma and Steve, and Nicola as well, though she's only here for another month or two. I went to work for that company about 10 years ago, and the main job was to work on footrot.

Footrot is endemic in New Zealand, and it's a big limitation to fine wool production. We've got Margot from Icebreaker here today, and companies like that are trying to increase their wool production. Pretty much Merinos hugged the Alps in New Zealand, because they'd go out of that area and get footrot and fall over and be no good. So my job, with a great team of people, was to help solve that problem through genetics. If you know anything about me, there's nothing you can't solve with genetics. That's pretty much our approach to everything.

And it proved to be so in sheep. I'm just going to run you through what we've been doing. There's a breeding value now for footrot, and there's work about to start here; literally, we'll get a contract in the next few days to start the work. So there's a really good space for foot health in Australia to piggyback on the work we've done in New Zealand and go forward. There's a video here I might have shown you before, of a couple of mobs of sheep. This is one group of sheep in a central progeny test in New Zealand.

This mob's sire wasn't very good for footrot, and they also weren't very good for worms. This is another mob of sheep that were very, very resistant to footrot. Hopefully you can pick a bit of difference between those two groups of animals. What we know is that sheep with sore feet absolutely suffer, and we need a solution to that. So what we did was start off with a scoring system. What we do now is score every foot under footrot challenge, so where footrot is occurring we score every foot on a scale from zero, being perfect, to five, being no good.

Footrot is heritable

What we proved was that footrot is heritable. No one's got footrot in Australia, I know, but if you've got a neighbour that has, 25 per cent of the variation in your neighbour's feet problems is due to genetics and 75 per cent is due to environment. What that means is there are sheep in there that can stand in footrot for the year and not get it. That's what we've got in New Zealand now. We've got sires that throw progeny you can literally keep throwing new footrotty sheep in with, and they won't get it.

If you ever need an example of the power of genes, look at disease traits, because it is insane to watch that happen. We've had the beauty of the last 10 years really seeing that evolve. We always think it's just the disease, the weather or the conditions, but there are also genes at play, and that's a really cool thing. Like every trait, there are lots of genes involved. Across all 26 non-sex chromosomes there's a little bit of variation for footrot.

Genetics is what anything I talk about comes back to, but other people have other interests. When we think about genetics, we often think, "What's the wool gene or the growth gene?" But every trait has heaps and heaps of variation, and across every chromosome a bit of the heritability for footrot is being accounted for. So there are thousands of genes at play in every trait, and footrot is no different. There's been a gene test in New Zealand that was based on one little set of genes, but this work shows there's so much more variation that we need to work on with footrot.

Knowing that it's a fully quantitative trait means the only way you win is through breeding. It's the same as every trait we're playing with in sheep: the only way you make gain is through estimated breeding values, or ASBVs, because that's the only way you can capture all that genetic variation. And it's through lots of hard work, generally, and in this case it's scoring feet. I don't know how many feet I've looked at over the years, but too many. Hopefully now, with a bit of a team around me, I don't have to look at too many more, but I seem to still end up on it.

Taking the work to Australia

Where we're going with this is what we did in New Zealand, and it's the same thing we're going to do in Australia: progeny test sires, then take those progeny and do the unthinkable and put them under conditions where footrot is prevalent. The only way you get this data is where footrot is on the go. The other thing we're doing at the same time is working with those breeders to look at scald, or ovine interdigital dermatitis, which is foot problems where Dichelobacter nodosus, the footrot bacteria, isn't present.

We're hoping those two things will be correlated, and I think this work will evolve into a breeding value for scald, or OID, and a breeding value for footrot. We know that foot health generally is a major issue for the industry, and footrot is only one of those problems. So we'll do this process for both scald and footrot. Essentially, we're going to work with ram breeders.

We're working with ram breeders to not just score some of those sires' progeny; we're going to send them away and get them footrotted as well, cull rams. We're also going to score foot shape. For the last couple of years we've been scoring the foot shape and structure of animals, and we want to do that at the same time as this work. What we know, and we saw this on Sunday when we were looking at some feet, is that you can have sheep with perfect feet that are still susceptible to footrot, and you can have sheep with awful feet that are actually resistant to footrot.

There seems to be a bit of a correlation, and it's a bit favourable, but neither of those things guarantees you anything. You actually have to look at the animal when it's under that particular disease challenge. So there's lots of stuff we're going to be looking at on sheep's feet. I do think feet are one of the biggest problems, particularly in the Merino game. We've obviously focused on other traits for a long time, and feet are one of our limitations. Anyone who's been running sheep in the last few years under wet conditions will have seen a bit of lameness around the place. So I reckon it's a pretty exciting project.

The cool thing is that footrot's not correlated with much, so we can make genetic gain without worrying about whether we're going to lose wool or lose growth or lose carcase. There is a small favourable correlation with worm egg count, so the sheep that are resistant to footrot are also resistant to worms, which is good. Obviously the immune system is at play somewhere: the immune system controlling worms, the immune system controlling feet, and both pretty good.

What the breeding value does in a mob

It's not a silver bullet, but it's pretty bloody good. This is our variation across the industry at the moment. It's all New Zealand data, because we don't have anything in Australia yet. Score four plus is where you've got under-running footrot and they're in serious problems. Score three is where you get a little bit of under-running. Score two is OID, or scald. At score one they don't have anything. So with a sheep that's a positive one for footrot, about half of its progeny will have under-running footrot.

And most of its progeny will at least have score three, so that's a really severe, angry lesion plus a bit of under-running as a minimum, in pretty much all four feet. So those sheep are in all sorts of strife. We've got sires now in this minus one range, and none of their progeny will have score four. I don't know exactly what the number is, but maybe 10 or 15 per cent have got a little bit of under-running and an angry lesion, and you've got a bit of score two stuff going on.

But there's a massive change in that mob and in how many of them are head bobbing. And that's just getting started. We've only been on this journey for 10 years, and really the first five of those years were us finding our feet, no pun intended. So we're now in this position where it's galloping ahead in New Zealand, and it's going to be awesome to see how we can do the same in Australia and really hook into it. We do appreciate that AWI and Animal Health Australia are coming on to help do this work. Animal Health Australia have already funded some preliminary work in Australia, so it's cool to see that all happening.

So that's the kind of stuff we're talking about. I've just put some gruesome images on, as if seeing King Charles in yoga gear wasn't bad enough. That's OID at its worst: really angry lesions, but there's no under-running there. Normally with footrot, for those who haven't seen much of it, you start with perfect skin there, obviously, but then it gets a little bit angry and you get some infection happening.

Then you get a really angry lesion, and once it opens up, that's when Dichelobacter nodosus, the footrot bacteria, can get in there. It's not a primary cause of foot problems; it's a secondary infector. It then starts to chew in here and starts under-running around here, and it works around and goes out to the toe. So we're trying to score all of that in the process. When you're doing that, it actually gets pretty addictive looking at sheep's feet, to be honest, because you see these subtle changes and you're always looking for those subtle things. When you add up all those averages at the end of the day, we'll have sires that have got not much going on and other sires with a heap of this going on, and obviously we can then make those selections. That's what the breeding value will help us through.

I think that's about it for me, Josh. You get to hear me later in the day as well. Thanks for having me.