Fur & Size Genes?

[Lindsay Krawsczyn]

So, I at this point am decently knowledgeable on coat color genes (not to say I can’t always know more, but I know more than a lot of people), buuuut I’m finding it hard to find resources on things like long hair genes in rabbits or what genes cause Giant breeds to be so huge. Sure, I already know via some light skimming of this website about how the genes that cause dwarf rabbits and the genes that cause lionhead manes work (even if I’m not sure how to add them to my genotypes and things as of yet). But say, if I breed a Flemish giant and a more regularly sized rabbit, what would be the outcome? Is it a recessive gene, so I’d most likely only get normal sized rabbits the first go around, or a dominant one? Or say, if I bred an angora into my mixbred line would I get angoras the first generation or would it happen more so second generation or so or is it like manes where they can have one copy of the gene and still have fluff but not as much? As an extension, how would long fur and manes interact, if anyone know. If nobody is sure about this stuff, I could always do some experiments of my own. After all, I know a guy with some Flemish Giants. And as for the mane X long fur combo, I do have some pretty decent maned genes in my herd. And I do believe I could get ahold of some angoras or something to the affect.

 

[judymac]

Angora is a recessive gene, so usually you would expect a first generation cross to have normal fur, but be a carrier of long hair. The code is L for normal coat, and l for angora. However, it has taken many generations to get a good quality, nicely crimped, dense angora coat of good length. There's a lot more involved than just 'l'.

Non-molting angoras like Germans are bred to have synchronous coats, that means the entire coat is of the same length, giving great uniformity to the sheared fiber. In opposition to that, my old-style English Angoras have triple coats--the outer coat 3-6" long, a middle coat 1-1/2 to 3" long, and another coat just emerging from the skin. This is a real boon to those who raise Angora rabbits in cold climates, especially since the rabbits molt every 12 weeks or so, which means there will always be a winter molt. I can pluck the shedding coat and still leave the rabbit with the intermediate coat intact, giving them more winter hair than the standard rabbit, even after a molt. However, this type of coat is a disaster for those that shear, leaving all sorts of short fibers embedded in the coat, that invariably shed out of the finished yarn. I don't know about any genetic studies on this, but I do know that crossbred Germans often have partially molting coats that can be difficult to deal with.

Betty Chu, renowned breeder of champion English Angoras, said that her 'bushel basket' line of non-molting English started with a doe that refused to molt unless pregnant. Betty realized this fault could be considered a blessing in the show ring, since a standard English only kept its full show coat for a few weeks before molting. Her non-molting line could keep growing fiber, making them look 'bushel basket' size, and be shown month after month in full coat. She kept selecting each generation from that first doe for longer and longer molt times. So it isn't a straight simple dominant/recessive gene.

Second generation angora crosses may have cute long hair, but they tend to have more coarse guard hair than 'purebred' Angoras, and less overall density. Future crosses selecting for fiber quality can make quick progress, though.

Some lines, like French, have naturally coarser guard hair that makes the high spike in the yarn. Some, like cottony English have guard hair so fine it seems like down, and the yarn is more cashmere like, very soft but less spike (fuzziness). I find these traits are genetic, but again, not completely a simply dominant/recessive. There's also the strength of the 'knob' on the awn hairs to consider, a weak attachment means the tip will likely break off and make a horribly shedding yarn. And the amount of crimp in the fiber, more crimp makes a more elastic yarn. Not to mention density--a good German could make 5 POUNDS of fiber in the same time an average Satin Angora may only give 5 useful OUNCES. Granted, the superfine satins may make a much finer fiber, which gives much less weight, but the German breeding program concentrates on proven production, not cute/shiny.

All this to say there are many polygenes (multiple genes working together) and modifiers involved in hair production, not just the recessive angora and satin genes. I find that more recent satin angora crosses tend to have coats more likely to mat and with poor fiber density and production. Future crosses selecting each generation for better coats does make a difference.

 

[Alaska Satin]

So, I at this point am decently knowledgeable on coat color genes (not to say I can’t always know more, but I know more than a lot of people), buuuut I’m finding it hard to find resources on things like long hair genes in rabbits or what genes cause Giant breeds to be so huge. Sure, I already know via some light skimming of this website about how the genes that cause dwarf rabbits and the genes that cause lionhead manes work (even if I’m not sure how to add them to my genotypes and things as of yet). But say, if I breed a Flemish giant and a more regularly sized rabbit, what would be the outcome? Is it a recessive gene, so I’d most likely only get normal sized rabbits the first go around, or a dominant one? Or say, if I bred an angora into my mixbred line would I get angoras the first generation or would it happen more so second generation or so or is it like manes where they can have one copy of the gene and still have fluff but not as much? As an extension, how would long fur and manes interact, if anyone know. If nobody is sure about this stuff, I could always do some experiments of my own. After all, I know a guy with some Flemish Giants. And as for the mane X long fur combo, I do have some pretty decent maned genes in my herd. And I do believe I could get ahold of some angoras or something to the affect.

Rabbit coat colors are an ideal intro to Mendelian inheritance because coat color, and coat type to a lesser extent, are mostly controlled by discrete genes that are inherited in a straightforward manner, and display pretty predictable dominance/recessiveness and gene interaction patterns. Many physiological characteristics, though, in rabbits and most other creatures, are controlled by multiple genes in non-Mendelian patterns, sometimes in linked, additive and/or interactive ways.

As far as I know, there is no single gene that produces a giant rabbit, in the way that the dwarf allele <dw> produces a dwarf rabbit. Giant rabbits are the result of selective breeding; their traits (large ears, heavier bone, etc) are related to increasing size, and depend on the intersection of some number of genes rather than any one particular gene. So when you cross a Flemish with a smaller breed, you usually get a range of sizes in the litter. Many may inherit the heavy bone and large ears of the Flemish, but they generally will not be as big or extreme as the Flemish parent. In fact, any extreme trait requires constant selection to maintain. This includes dwarf rabbits which, if they are not constantly selected for small size, will get bigger than the standard requires, even as they retain the smaller-than normal ears, round head and short legs produced by the dwarf gene.

If you want to investigate further, chapter 8 in The Genetics and Genomics of the Rabbit (ed. L. Fontanesi, 2021) gives a pretty exhaustive 25-page table of known morphological and physiological traits and disorders, and the inheritance and molecular genetics behind them.

As @judymac points out, wool comes from the homozygous allele <ll>, but the qualities of the wool depend heavily on many other genes and modifiers (some known, some not). It is notated in the lower case <l> as a recessive allele, but in some cases it actually functions like a partial recessive; sometimes a rabbit heterozygous for the wool gene <Ll> will have slightly longer, thicker and denser fur. So, breeders of numerous breeds have added an angora to their lines to improve fur density and length. Holland Lops are one example, which is one reason that Holland fur is relatively long and dense, and why "fuzzies" pop out of purebred Hollands fairly regularly.

So, while a homozygous non-wool rabbit <LL> bred to an angora <ll> will give you all non-wool coats (though they may have longer, denser fur), many breeds already have that wool gene lurking in the background. It will show up when you cross an angora with your unknown wool carrier, in babies that are woolly in the first generation. This happened in our barn when my daughter bred a beautiful purebred white Satin buck (with great density!) with her French/Satin Angora doe. Her aim was to improve body type in the long run, but in that first generation, half the babies were woolly! It was an all-around success, too, as one of the babies with a French coat went on to win BIS at an ARBA youth show, and even placed in the meat show at the fair, which was, to that point, unheard of for an angora! In further agreement with @judymac, the bunnies with satinized wool were a lot higher-maintenance and much more prone to matting and felting.

Again, if you want to read into the gritty details of rabbit fur and fiber genetics, see chapter 7 by D. Allain in the same book mentioned above - The Genetics and Genomics of the Rabbit.

As far as interaction between angora <ll> and maned <M_>, I've not heard or read any discussion of that; it's an interesting question. All I have to offer is that it probably wouldn't be done by most Lionhead breeders. Lionheads have a particular pattern to their wool growth, with disqualifications for wool longer than 1" on the face, for heavy wool more than halfway up the ears, for any wool at all in the saddle area, and for lack of a clean area of normal fur between the mane and the side and flank wool. It's actually a very difficult thing to breed a Lionhead that truly adheres to the standard. And since the angora gene causes wool to develop all over the body, and sometimes on the head and ears as well, <ll> would most likely wreak havoc with the distinctive look of the mane and flank wool on a Lionhead. But since the two fur types are assumed to be on different genes, you possibly could have a rabbit that was homozygous for both <ll> and <MM>.

If you're interested in the molecular genetics of fur development, an interesting article is here:
Rabbits – their domestication and molecular genetics of hair coat development and quality
https://onlinelibrary.wiley.com/doi/10.1111/age.13024

 

[Lindsay Krawsczyn]

Rabbit coat colors are an ideal intro to Mendelian inheritance because coat color, and coat type to a lesser extent, are mostly controlled by discrete genes that are inherited in a straightforward manner, and display pretty predictable dominance/recessiveness and gene interaction patterns. Many physiological characteristics, though, in rabbits and most other creatures, are controlled by multiple genes in non-Mendelian patterns, sometimes in linked, additive and/or interactive ways.

As far as I know, there is no single gene that produces a giant rabbit, in the way that the dwarf allele <dw> produces a dwarf rabbit. Giant rabbits are the result of selective breeding; their traits (large ears, heavier bone, etc) are related to increasing size, and depend on the intersection of some number of genes rather than any one particular gene. So when you cross a Flemish with a smaller breed, you usually get a range of sizes in the litter. Many may inherit the heavy bone and large ears of the Flemish, but they generally will not be as big or extreme as the Flemish parent. In fact, any extreme trait requires constant selection to maintain. This includes dwarf rabbits which, if they are not constantly selected for small size, will get bigger than the standard requires, even as they retain the smaller-than normal ears, round head and short legs produced by the dwarf gene.

If you want to investigate further, chapter 8 in The Genetics and Genomics of the Rabbit (ed. L. Fontanesi, 2021) gives a pretty exhaustive 25-page table of known morphological and physiological traits and disorders, and the inheritance and molecular genetics behind them.

As @judymac points out, wool comes from the homozygous allele <ll>, but the qualities of the wool depend heavily on many other genes and modifiers (some known, some not). It is notated in the lower case <l> as a recessive allele, but in some cases it actually functions like a partial recessive; sometimes a rabbit heterozygous for the wool gene <Ll> will have slightly longer, thicker and denser fur. So, breeders of numerous breeds have added an angora to their lines to improve fur density and length. Holland Lops are one example, which is one reason that Holland fur is relatively long and dense, and why "fuzzies" pop out of purebred Hollands fairly regularly.

So, while a homozygous non-wool rabbit <LL> bred to an angora <ll> will give you all non-wool coats (though they may have longer, denser fur), many breeds already have that wool gene lurking in the background. It will show up when you cross an angora with your unknown wool carrier, in babies that are woolly in the first generation. This happened in our barn when my daughter bred a beautiful purebred white Satin buck (with great density!) with her French/Satin Angora doe. Her aim was to improve body type in the long run, but in that first generation, half the babies were woolly! It was an all-around success, too, as one of the babies with a French coat went on to win BIS at an ARBA youth show, and even placed in the meat show at the fair, which was, to that point, unheard of for an angora! And in further agreement with @judymac, the bunnies with satinized wool were a lot higher-maintenance and much more prone to matting and felting.

Again, if you want to read into the gritty details of rabbit fur and fiber genetics, see chapter 7 by D. Allain in the same book mentioned above - The Genetics and Genomics of the Rabbit.

As far as interaction between angora <ll> and maned <M_>, I've not heard or read any discussion of that; it's an interesting question. All I have to offer is that it probably wouldn't be done by most Lionhead breeders. Lionheads have a particular pattern to their wool growth, with disqualifications for wool longer than 1" on the face, for heavy wool more than halfway up the ears, for any wool at all in the saddle area, and for lack of a clean area of normal fur between the mane and the side and flank wool. It's actually a very difficult thing to breed a Lionhead that truly adheres to the standard. And since the angora gene causes wool to develop all over the body, and sometimes on the head and ears as well, <ll> would most likely wreak havoc with the distinctive look of the mane and flank wool on a Lionhead. But since the two fur types are assumed oto beon different genes, you possibly could have a rabbit that was homozygous both both <ll> and <MM>.

If you're interested in the molecular genetics of fur development, an interesting article is here:
Rabbits – their domestication and molecular genetics of hair coat development and quality
https://onlinelibrary.wiley.com/doi/10.1111/age.13024

Ooook, so. About what I was expecting honestly. It felt weird to me originally honestly that dwarf genes where so simple, as a lot of the time once you get into things like sizing it gets really complicated really fast. So, it definitely checks that giants are made using a bunch of different genes. And Angora being recessive was also about what I expected, seen as it just didn’t give off the, and I’m not sure if this makes sense, feel of a dominant gene.

However, this does give me a whole slew of ideas for new genetic experiments I could do. Like, I’ve always wondered what would occur if I took a fur type that generally has longer fur and mixed it with rex fur. I’ve got a few little double maned rabbits at this point, and my neighbor has this mini Rex buck and he’s offered to let me use his bucks for studs before. So, I have access to rabbits for that experiment. And then of course there’s the ‘what happens if you have both angora fur and the mane’, which as much as I don’t have the rabbits for that on hand I could get ahold of them. And hen that opens up a whole new possibility of say, angora + Rex or angora + rex + maned. And who knows, maybe screwing around with it I’d figure out genes where related in ways we didn’t even realize.

Aaand then there’s the slightly scary idea of trying to somehow both giant and dwarf simultaneously. Which, sounds like a very hard nope honestly buuuut I mean. . . cursed giant dwarf. If you tried hard enough, you might be able to do it honestly. I have no idea and I do not want to try

 

[kusanar314]

Aaand then there’s the slightly scary idea of trying to somehow both giant and dwarf simultaneously. Which, sounds like a very hard nope honestly buuuut I mean. . . cursed giant dwarf. If you tried hard enough, you might be able to do it honestly. I have no idea and I do not want to try

If you do this one I want to see the results! That sounds hilarious.

 

[RabbitsOfTheCreek]

If you do this one I want to see the results! That sounds hilarious.

It wouldn't be hilarious if a bunch of problems come up, like if the Doe is the Dwarf
Or if she's the bigger one and ends up crushing the dwarf Kits

 

[kusanar314]

It wouldn't be hilarious if a bunch of problems come up, like if the Doe is the Dwarf
Or if she's the bigger one and ends up crushing the dwarf Kits

Obviously you wouldn't breed them if the doe is the dwarf.

And for her crushing the dwarf kits, does seem to crush their own kits that are a normal size for them if they stand on them, I wouldn't expect anything different out of the giant doe.

If you're really worried about crushed kits, breed a few small does at the same time and foster out any small kits and give the giant girl the bigger ones.