Felting Lustre Mutant Sheep
Searching for the genetic markers for the structure of wool at AgResearch
In a bid to increase the value of wool (and with it the profitability of sheep farming) AgResearch has a research programme looking at understanding the genetic factors that govern wool fibre structure. Wool is largely composed of proteins and there is variation in protein composition between breeds but the differences are subtle and would require large sample sizes to identify what those differences are.
Another approach is to study unusual wool from mutant sheep, in particular a merino mutant with wool that is straight and silky (lustrous) rather than crimped and dull. The hope is that with the knowledge gained they may eventually be able to breed sheep with designer wool types for specific end uses.
About one sheep in 10 million is born with a mutation described as “felting lustre”. Instead of being crimped and dull it is straight and shiny, and looks a bit like an angora goat. Later in life they can produce wool that is more like mohair but most of these sheep don’t generally live that long. They often have problems with teeth, skin and lungs, don’t tolerate cold and their wool is cotted and hard to shear, so they usually die early or end up as dog tucker.
AgResearch wool scientists Dr David Scobie and Dr Jeff Plowman were aware of this mutation and figured it could be useful in research, and so sent out a call for living examples. They were subsequently gifted a few that were hardy enough to survive a cold winter.
The first robust female they worked with was named Maxine. She was mated to an ordinary composite ram and in due course gave birth to Sharon, a strong, healthy ewe with silky, straight wool.
“The felting lustre trait is a single gene mutation and is dominant. You can have normal parents and it doesn't really matter what their wool is like, the lamb will come out looking like an angora goat and the wool it produces later in life will probably look very much like mohair,” Jeff says.
“The main reason for our being interested in it is that we have been looking at proteins and how they relate to fibre structure. Proteins comprise 98% of the total content of wool and keratin is about 85% of the total protein content. These mutations are a radical change in fibre structure and in protein composition. There is maybe one gene involved in the mutation but there are a dozen or so proteins affected by it and they can change the internal structure of the fibre quite dramatically.
“So if we can figure out how these proteins influence fibre properties we could use them as a breeding type marker. Bulk is quite an important characteristic in wool and is influenced by curvature so if we can control curvature we can maybe design our sheep to produce better fleeces.”
Bulk is the opposite of lustre, it comes from a lot of crimp and these sheep lack crimp. Whereas Merino wool might normally have about 20 crimps per inch these mutant wools have two or 2.5 crimps.
David Scobie says that this single gene mutation may have a number of effects. “We see things like tooth eruption changes and they may also have a bit of trouble breathing but it is a single gene that has led to the change in wool characteristics! So somewhere down that chain of events, if we can find out a little bit more about it, we might be able to get closer to getting control of those wool characteristics. We don't necessarily want this gene but there are others that would be handy to manipulate,” says Scobie.
“Currently the price of mohair is much higher than wool and maybe you could use this felting lustre wool as a mohair substitute. However, the wool from these mutant sheep seems to cot very easily, which makes the sheep difficult to shear and the wool difficult to process.”
The expectation is that a more detailed understanding the protein structure of wool will lead to the discovery of genetic markers that will allow farmers to breed sheep with more favoured types of wool with, say, mohair-like characteristics or the opposite. Once we know where that gene lies we can find other versions that might give us more crimp for example and therefore more bulk. It probably wouldn’t be the felting lustre mutants that are used as the basis for change because of their lack of hardiness, but armed with that knowledge it may be possible to create variations in other breeds.
However, at present all that is speculation. Right now, says Jeff, they need a lot more scientific information before they can start producing new types of wool. “We are not trying to breed these sheep yet. We are trying to understand what drives structure and how we can actually look for markers so that if you emphasise a certain marker you can produce sheep with different quality of wool,” says Jeff. “In recent times the industry has gone away from breeding for wool to breeding for meat, except in the case of Merinos, and we want to get the industry focused again on producing higher quality and higher value wool.”