Different Breeds

    There are 45 different rabbit breeds recognized by the ARBA. They range from the 2.0 pound Netherland Dwarf to the 15+ pound Flemish Giant. To look at a picture of each breed, go to http://www.arba.net/photo.htm. Here, I will provide an brief outline of some of the more popular breeds. (references: ARBA official guidebook and the Standard of Perfection)

Giants

Name Ideal Weight Varieties
Checkered Giant 12 pounds Black, blue
Flemish Giant 15 pounds Black, blue, fawn, light gray, sandy, steel gray, white
Giant Chinchilla 13-14 pounds Chinchilla

Mediums

Name

Ideal Weight

Varieties

Californian 9 pounds One-white with black nose, ears, and feet.
Champagne D'Argent 10-10.5 pounds One type-the name means "French Silver"
English Lop 10 pounds Agouti, broken, self, shaded, ticked, wide band
French Lop 11 pounds Agouti, broken, self, shaded, ticked, wide band
New Zealand 10-11 pounds White, red, and black
Palomino 9 pounds Golden and Lynx
Rex 8-9 pounds black, black otter, blue, Californian, castor, chinchilla, chocolate, lilac, lynx, opal, red, sable, white, seal, and brokens
Satin 9.5-10 pounds Black, blue, Californian, chinchilla, chocolate, copper, red, siamese, white, broken group

Smalls

Name

Ideal Weight

Varieties

Dutch 4.5 pounds Black, blue, chocolate, gray, steel, tortoise
English Angora 5.5-6.5 pounds Agouti, pointed white, self, shaded, solid, ticked
English Spot 6-7 pounds Black, blue, chocolate, gold, gray, lilac, tortoise
Florida White 5 pounds white
Harlequin 7.5 pounds Japanese (orange + color) and Magpie (white + color), both in either black, blue, chocolate, or lilac
Havana 5-5.5 pounds Black, blue, chocolate
Mini Lop 5.5-6 pounds Agouti, broken, pointed white, self, shaded, solid, ticked
Tan 4.5-5 pounds Black, blue, chocolate, lilac

Dwarfs

Name

Ideal Weight

Varieties

American Fuzzy Lop 3.5 pounds Agouti, broken, pointed white, self, shaded, solid
Britannia Petite 2.5 pounds White, agouti
Dwarf Hotot 2.25 pounds One-white with black eye bands
Holland Lop 3 pounds agouti, broken, pointed white, self, shaded, solid, ticked
Jersey Wooly 3 pounds Agouti, Pointed white, self, shaded, tan pattern
Mini Rex 4 pounds Blue, Californian, castor, chinchilla, lynx, opal, red, seal, tortoise, white, broken group
Netherland Dwarf 2 pounds Technically only selfs, shaded, agouti, and tan pattern, but also there is "any other variety", so really any color
Polish 3.5 pounds black, blue, chocolate, BEW, REW, broken group

 

 

Origin of the Holland Lop

    The Holland Lop was developed by Adriann DeCock of Telborg. It is a Dutch breed, originally developed by crossing French Lops and Netherland Dwarfs. In 1952, a doe from these litters was breed to a English Lop. This cross, and breeding between the offspring from it, was the beginning of our current-day Holland in 1955.

    An overview of the current Holland Lop standards is as follows: Holland lops are a 4-class breed, meaning that they are shown as Juniors and Seniors in their color group. There are two colors groups, Broken and Solid. Juniors are less than 6 months of age, seniors are over. Holland lops should be massive and heavy set. They should have well-rounded features and heavy bone. The ears should be think, well rounded, and the ears openings should be turned in towards the body. The heads should be large, and the length of head to body ratio should be about 1:2. The Holland Lop body should have good depth in the hindquarters and shoulders, and should be well-rounded. The topline should carry straight back from the shoulders and slope gently to the ground. It should not flatten out anywhere on the slope. Most of the weight when properly posed should be resting on the hind feet. The front feet should be gently touching the ground. The Holland lop should weigh no more than 4 pounds. They should have roll-back fur, meaning that the fur gently 'rolls-back" into to the correct position.

 

 

Caring for a Rabbit 101

    Hollands can live comfortably in a cage 18"x24"x14" high. Breeding does will do better with a cage 24"x24". Fresh water and hay should be available at all times. Does nursing and Hollands in the summertime consume more water. Does with kits and kits should be able to free-feed, meaning eat as much as they want, as long as they aren't getting fat. Treats such as carrots and from a pet store should be feed sparingly. Fresh food should never be feed to any rabbit under the age of six months. The cage should never have a bad odor. If it does, it needs to be cleaned. The cage should never get to that point though, as rabbits are normally quite clean animals. Both bucks and does make equally good pets, it just depends on the rabbit's particular personality. Adult bucks who aren't neutered have a tendency to spray urine, and does who aren't spayed can become territorial when in their cage. But, it just depends on the individual rabbit.

 

 

Genotyping Rabbits

    Genotyping a rabbit is not as hard as it may seem. All that is needed is basic knowledge of rabbit color genetics, breeding records, and the rabbit's pedigree with the correct colors written on it.

  1. Figure out the rabbit's color

  2. Write down the genotype for that color, if there is a dominant gene, leave a space next to it to fill it in. (Check my "genotypes" list for help if needed)

  3. Look at the sire's color and find the genotype for that

  4. Fill in any blanks-like if the rabbit has to carry a recessive gene because the sire has it

  5. Do steps 3 and 4 for the dam

  6. Look at the breeding records-what colors did the rabbit have or sire? For example, if the rabbit is black, but there was a blue in the litter, then the rabbit has to carry dilute. Fill in any missing blanks from this information that is possible.

  7. Now what is written for the rabbit's genotype is what is known. But, if the gsires, gdams, ggsires, and ggdams are looked at then it can be guessed what else is carried.

Here's an example:

  1. Rabbit's color: Black

  2. Genotype: aa B_ C_ D_ E_ enen

  3. Sire's color: Blue    Genotype: aa B_ C_ dd E_ enen

  4. Fill in blanks: aa B_ C_ Dd E_ enen

  5. Dam's color: Broken chocolate tort   Genotype: aa bb C_ D_ ee Enen

  6. Fill in blanks: aa Bb C_ Dd Ee enen

  7. Breeding records show that the rabbit has sired litters with the following colors: black, blue, chocolate, blue tort, and a REW

  8. Fill in: aa Bb Cc Dd Ee enen

  9. Ta-da! The rabbit's genotype!

Of course, it doesn't always work out that the genotype is completely filled out, but it helps to give a clue at least. It can be tested too; to learn what a rabbit may carry. For example: if it is a blue rabbit that is thought to possibly carry REW, then breed the blue rabbit to a REW and see! Of course, the rabbit may not throw the REW gene, but if this is done enough so there are at least 10 or so offspring and no REW's show up, then chances are it doesn't carry REW. And, if a REW does pop up in a litter, then it does carry REW!

 

 

Peanuts vs. Max Factors

The terms "peanuts" and "Max factors" are thrown around a lot when there are abnormal and/or extra tiny kits in litters. These kits usually die within the first two weeks, often the first couple days after they are born. There is a difference between the two, not only in what they look like, but also what causes them.

A peanut is a kit that is abnormally tiny, usually with a large head and protruding eyes. Their legs and hips are not always totally developed and can be crossed. Pituitary dwarfism is the "technical" term for what causes peanuts. The pituitary gland is the master gland that controls the entire endocrine system. (The endocrine system consists of all the glands in the body.) Besides controlling all other glands, it controls the secretion of the growth hormone. In peanuts, there is a genetic defect that causes the pituitary gland to malfunction and it will not release enough growth hormone to sustain the kit. As a result, the kit dies.

Pituitary dwarfism happens when a kit inherits two dwarf genes. A normal dwarf rabbit has a normal gene (Dw) and a dwarf gene (dw). Its genotype is Dwdw. A peanut has the genotype dwdw. Having two dwarf genes causes the lethal combination. On average, one kit in every four will be a peanut. This is shown in the Punnett Square below with a cross between two normal dwarfs:

Dw

dw

Dw

DwDw

(big dwarfs)

Dwdw

(dwarf)

dw

Dwdw

(dwarf)

dwdw

(peanut)

Okay, now for Max factors. They are very different from peanuts. Max factors happen all because of a rabbit named Max. Max was a dwarf brought over to the United States from Germany to help improve the US’s dwarf lines. While he was used for mostly Netherlands, he also aided with the improvement of Holland Lops. His lines flow through quite a few of the dwarf breeds. While most likely the gene that causes a Max factor was around before Max (the rabbit), it didn’t have a name. The Max factor is a normal recessive gene that causes the kit to be born with any or all of the following:

Open eye(s): while not lethal in itself, if often causes eye infections that most likely will lead to blindness.

Deformed Limbs: Usually one or more limb is twisted, or at least display severe "splay legs".

Weird feet: Most of the time they have flipper feet, which are webbed. They have been known to have dewclaw on their hind foot (feet).

Spiked/soft fur: Max factors if they live can have funny-looking spiked fur or extremely soft cottony fur because they lack guard hairs.

Max factors do not always die. While most die within the first two weeks of life, if allowed to live they can lead good lives. Also, it has been said that a lot of winners carry the Max factor gene. This may be a direct correlation or just coincidence-it depends on who is asked.

So…that’s the difference between Max factors and peanuts. Hope it helps!

 

 

Breeding Techniques

    There are different ways of breeding rabbits. It isn't always as simple as taking the buck to the doe and letting nature take it's course. While that is by far the easiest, there are different theories of the best way to breed rabbits to get the highest number of conceptions and larger litters.

    One way is to take the doe to the buck's cage, and, if they aren't hurting each other, just leaving them together. Watch first and make sure the buck does get a good mount (he'll grunt and fall of to the side). Then just let them be for a few days-checking of course to make sure they're getting along. It's a simple and easy way to breed, but it can be dangerous to just leave them together unsupervised. Often though, it does increase litter size because the buck gets more good mounts.

    Another way that I find quite good is to take the doe to the buck, let him get one good mount, then separate them. In one hour, take the doe to the buck again, let him get a good mount, separate them. Repeat again in twelve hours, and then twelve hours after that. (So a total of four times, hour zero, one, twelve, and 24). I have good luck with this technique, and my Holland's litter size average is 4-5.

    Sometimes the bucks are just too comfortable in their cage and don't want to breed. In this case it helps to get them in a new environment-namely the table. A grooming table or some other table with a carpet square on it works well. Put the buck on the table first, let him get a bit accustomed to it, then bring him the doe. Let him mount once or twice, and put them both back. Follow the same thing as above-doing four or so breedings-just put them on the table instead of the buck's cage.

    If the bucks are uncooperative, they may be lazy or fat. Usually this can be solved by just not feeding them right before they are breed. Wait until evening to breed, then after he services the doe feed him. More often though, it's the does that are not very cooperative. Rabbits do have a cycle (about every 12 days), contrary to common belief, so wait a day or two and try again. If the doe is continuously not cooperative, then a forced breeding can be tried. Just support her hindquarters with one hand, lifting it up and out slightly (sometimes moving her tail out of the way is helpful to the buck) and hold her head/upper body down gently, but firmly with the other hand. Some bucks don't like the person getting involved and refuse to breed, but after some time they do seem to get used to it.

    Good luck! Don't forget to write down the date they are breed/days the are breed and mark the calendar 31 days from then!

 

 

 

 

 

 

Pros and Cons of Color Projects

 

    Color projects are fun and interesting. They do add some difficulty though, as usually the rabbits aren't as well typed as the normal colors are.

Pros:

  1. Keeps things interesting

  2. Provides a greater challenge

  3. Makes winning all the more fun to win with a "color"!!

  4. Sets the breeder apart from the rest

  5. The satisfaction of going out to the barn and seeing all the nicely typed "colored" rabbits

Cons:

  1. Can be more expensive to start, as most often they are rare colors and hard to find

  2. Some judges don't like the newer or rare colors

  3. It can be frustrating if it seems like no progress is being made

  4. Having a color project means two things are being worked on-type and color-instead of just type.

  5. Color projects often take up more space

In my opinion though, working on colors is a blast and is worth the extra effort. One look at my typy siamese sables and tri's make everything worth it. Showing is more fun as well-like when my sable point doe won BIS! It also keeps things fun in the long cold winters here in Michigan :o)

 

 

 

 

 

Developing a "Line"

 

    Breeders often talk about having their own "line". It is seen on pedigrees too with the rabbitry initials or breeder's last name being in front of the rabbit's. It takes a while to get a line started, and it's not something that just happens overnight. Here are some ideas on how to get a line started:

 

 

 

 

 

 

 

Cull Doesn't Always Mean "Kill"

 

    The word "cull" brings on bad feelings and thoughts often, because people think it means to kill. Often, this is not what a breeder means when he/she says "cull". The dictionary definition of "cull" is: "To pick out from the others, to select, to select from the others because of inferior quality". No where in that is the word "kill". When most breeders cull their herd, they go through and pick out the ones that just aren't as nicely typed as the rest. These often get sold as pets. Although they may not be the top quality the breeder wants, they are usually fine animals that would be quite good pets. Or, some breeders when the cull their herd have such a great quality of animals that the ones they cull are perfect for starter rabbits for other to breed. Another alternative for those that are terrific, just not the best, are to become 4-H project animals. Cull often does NOT mean "kill".

 

 

 

 

 

 

Rabbit Gene List

Gene

Description

Examples

A

Agouti gene: light eye circles, belly, and triangles. Has banding on hair shaft. Chestnut, Opal, Orange, Lynx, Chinchilla

at

Tan Pattern: Solid color, has tan, fawn, or white eye circles, belly, and triangles. Silver Martin, Tan, Otter

a

Self: No banding on hair shaft, one color throughout Blue, Chocolate, Black, Tort

B

Black: When present with Agouti gene, causes a black band, when present with the Self gene, produces one solid color. Black, Chestnut

b

Brown (or Chocolate): With Agouti, makes the black band brown, when present with the Self gene, makes solid chocolate instead of black. Chocolate, Lynx

C

Full Color: All four dark brown and all three yellow pigments bands to be present. Completely dominant. Any color except Chinchilla (light or dark) or REW.

cchd

Dark Chinchilla: Same as full color, except only one yellow pigment band. Dominant over cchl and c genes. Chinchilla, Squirrel

cchl

Light Chinchilla: Only allows two dark brown pigments and no yellow pigments, which lightens the color. Incompletely dominant, is dominant over only the ch and c genes. Sable Point, Siamese Sable, Smoke Pearl

ch

Himalayan (Pointed White): Causes the color to be only on the "points"; ears, nose, feet, and tail. Can produce red eyes. Dominant only over the c gene. Pointed White, Himalayan, Californian

c

Albino: Stops all color from being expressed. Produces a white rabbit with red eyes. Ruby-eyed White

D

Dense Coat: Full color, much like the dominant C gene. Eyes are brown. Orange, Chestnut, Tort

d

Dilute: Much like its name, it dilutes the color (e.g. Black to Blue, Chocolate to Lilac, etc.). Eyes: Blue-gray Cream, Lilac, Blue, Opal

E

Normal Extension: Works with the C loci, lets the dark brown pigment be fully expressed Black, Blue, Chocolate, Lilac, Siamese Sable

Es

Steel: When Agouti is present, covers up the middle band of dark pigment and darkens the eye circles, belly, and triangles. Leaves white guard hairs also called "ticking". Gold Tipped Steels, Blue Tipped Steels

ej

Japanese Brindling: Works with Agouti to allow the dark brown and yellow pigments to stay in separate areas instead of on the same hair shaft (like a mosaic). Harlequin, Tri-Color, Magpie

e

Non-Extension: Works with the C loci and modifiers to remove most or all of the dark pigment leaving only the yellow pigment. Red, Orange, Fawn, Cream

En

English Spotting: Causes white spots within the solid color, also called Broken. Works with the plus/minus modifiers to intensify or decrease the amount of white. English Spot, Tri-color, any Broken EnEn = "Charlie", too much white

en

Self-Colored: Normal color, no white spots Any selfs.

Enen = normal broken, enen=self.

Du

Absence of Dutch Pattern: Causes a "normal" colored rabbit, no partial white/color pattern. DuDu = no pattern

Dudu = partial Dutch pattern

du

Dutch Pattern: Causes a pattern where there is a white triangle on the face, white belt around the middle, and white boots on the back feet. Dutch

V

Absence of Vienna White: "normal" colored rabbit. VV will result in a "normal" rabbit. Vv = patches of white like the dutch pattern

v

Vienna White: Causes a white rabbit with blue eyes. vv = Blue Eyed White (BEW)

W

Normal Width: Normal coloring, allows the middle yellow or white band to remain the same. Agouti, Chinchilla

w

Double Width: Allows the middle yellow or white band to double, which colors the agouti pattern areas (triangles, eye circles, and belly). New Zealand Red

Si

Non-Silvering: Has no effect on color Basically all rabbits

si

Siver: Creates silver-white tipped hairs and silver-white hairs that intermingle with the normal colored hairs in the coat. Silver Martin, Silver Fox

 

 

 

 

 

 

BREEDING RABBITS 101

BEFORE BREEDING-most of this is all prep work!

  1. Before you even breed, here are some different things to think about:
  1. Know your lines. By this I mean, the families that the buck and doe came from. This can be seen on the pedigree, and is the first part (prefix) to the rabbit’s name (EX: Naragon’s Nike would be Todd Naragon’s lines-to find a list of the prefix names go to www.islandgems.net and look for the link to it) Some lines are not "compatible". This can take some research and just general knowledge.
  2. Have a nestbox built, bought, or to be built/bought soon! The nestbox needs to be given to the doe, filled with fresh straw, at 26 days after being breed.
  3. Have some goals in mind. Are you trying for better type (better show quality) or is this more for color variety, or both? Breeding "just to see what happens" is NOT a goal, and is what often leads to problems. At least have some ideas on what you want to learn and accomplish. If it’s just to raise your own rabbit, then that’s fine, but have some pre-set goal.
  4. Breeding Theories:

  1. Keep good records! Get a 3-ring binder. I find it easiest to use page protectors and slide the pages in. Records you need to keep are: Pedigrees, breeding records, expense records, and a list of contacts for people interested in buying the babies later on. If you show, keep the show records.
  2. Ok, now for deciding how to actually breed.

    There are different ways of breeding rabbits. It isn't always as simple as taking the buck to the doe and letting nature take it's course. While that is by far the easiest, there are different theories of the best way to breed rabbits to get the highest number of conceptions and larger litters.

    One way is to take the doe to the buck's cage, and, if they aren't hurting each other, just leaving them together. Watch first and make sure the buck does get a good mount (he'll grunt and fall of to the side). Then just let them be for a few days-checking of course to make sure they're getting along. It's a simple and easy way to breed, but it can be dangerous to just leave them together unsupervised. Often though, it does increase litter size because the buck gets more good mounts.

    Another way that I find quite good is to take the doe to the buck, let him get one good mount, then separate them. In one hour, take the doe to the buck again, let him get a good mount, separate them. Repeat again in twelve hours, and then twelve hours after that. (So a total of four times, hour zero, one, twelve, and 24). I have good luck with this technique, and my Holland's litter size average is 4-5.

    Sometimes the bucks are just too comfortable in their cage and don't want to breed. In this case it helps to get them in a new environment-namely the table. A grooming table or some other table with a carpet square on it works well. Put the buck on the table first, let him get a bit accustomed to it, then bring him the doe. Let him mount once or twice, and put them both back. Follow the same thing as above-doing four or so breedings-just put them on the table instead of the buck's cage.

    If the bucks are uncooperative, they may be lazy or fat. Usually this can be solved by just not feeding them right before they are breed. Wait until evening to breed, then after he services the doe feed him. More often though, it's the does that are not very cooperative. Rabbit does do have a cycle (about every 12 days), contrary to common belief, so wait a day or two and try again. If the doe is continuously not cooperative, then a forced breeding can be tried. Just support her hindquarters with one hand, lifting it up and out slightly (sometimes moving her tail out of the way is helpful to the buck) and hold her head/upper body down gently, but firmly with the other hand. Some bucks don't like the person getting involved and refuse to breed, but after some time they do seem to get used to it.

  3. Now you are ready to breed them. Good luck! Remember the nestbox at about 26 days.
  4. If she doesn’t have a litter, or has a DOA (dead on arrival) litter, re-breed her right away. She will be the most receptive to the buck, and if you wait too long it will be about 2-3 weeks usually before she will be willing to breed again.
  5. Here are some websites that may be helpful:

 

 

 

 

 

 

 

Rabbit Coat Color Biochemistry

 

Melanin
Melanin is the most basic color pigment. There are two different main types of melanin that produce pigment: Eumelanin and pheomelanin. eumelanin is the range of dark brown to almost black pigments, and pheomelanin creates the yellow pigment. Both of these pigments are created from the same biochemical pathway that branches. Tyrosin changes via the enzyme Tyronease into Dopaquinone. It is from this that the eumelanin and pheomelanin pathways branch out.

The Agouti (A) Locus
On an Agouti hair shaft, there are three bands of color. There is a slate under color, which is a result of eumelanin. The second is an orange band, which is a result of pheomelanin. The top band is black, which is caused by dense eumelanin. The cause of this is a peptide called the ASIP (Agouti Signaling Protein). ASIP signals production of pheomelanin production in the melanocytes, the cells that produce pigments. There is a receptor on the melanocytes called “melanocortin receptor 1” or Mc1r. This receptor is also known as the “E” or extension locus. When it binds, it results in producing pheomelanin.

For the Tan Pattern (ata), there is no ASIP expressed on the eye circles, belly, and triangles at the neck, feet, legs, and inside of ears. Because of this, only pheomelanin is produced in these areas, and not the darker eumelanin.

The Self-Pattern (aa) is caused by ASIP being absent, which allows the eumelanin production is seen on the entire coat of the animal.

The Brown Locus:
The gene product called Tyrosinase related protein Type I (or, TYRPI) causes the brown intermediate band of eumelanin into eumelanin black. Animals with a mutation leading to inactive gene products cannot produce eumelanin in a mature form. Because of this, the chocolate is displayed because the black doesn’t cover it up. In cases where the reds, orange, and fawn rabbit colors are “smutty”, or show excessive dark pigments, the chocolate gene will correct this as it hides the dark pigments, without loosing intensity. The chocolate gene has no affect on pheomelanin, unlike the dilute gene which will cause the color to loose intensity.

The Color Locus:
The C locus encodes the gene for the enzyme Tyrosinase. Mutations of this enzyme result in altered levels of melanin production, which changes the rabbit’s coat color. Total inactivation of Tyrosinase causes albinism, which occurs when the C gene substitutes the A gene in the coding series.

Some mutations cause different levels of activity, such as what happens with the Chinchilla and Himalayan genes. In temperatures below 37 degrees Celsius, the activity decreases in the C Locus. This affect is most easily seen in the Himalayan. Normal Tyrosinase activity occurs at 37 degrees Celsius. This temperature allows for the melanin production. The change in the melanin production is what causes the chinchilla, shaded (such as Siamese Sable), and Himalayan colors.

For the Chinchilla allele, the effect on eumelanin production is hard to see. Some “black” rabbits may actually be homozygous for the Chinchilla gene. In other words, their genotype for the C locus is cchdcchd or cchlcchl. This is when the color Seal occurs, as there is very slight shading that can usually be seen in direct sunlight. When the dark chinchilla gene is homozygous, the rabbit is very black and there may not be a visible difference. In Chinchillas, the levels of eumelanin are lower than the levels in a Chestnut. The removal of the yellow pigment is what causes the Chinchilla’s color.

List of the C Locus Genes and Melanin Production
C Complete tyrosinase activity
cchd Reduced eumelanin, eliminated pheomelanin production
cchl Light shading, pheomelanin production not totally eliminated
c Inactive tyrosinase
ch Temperature sensitive mutation, where the change in temperature caused by the gene changes the melanin production


Dilute Locus
Contrary to what might be thought, the dilute gene does NOT change the coat pigment. For example; the pigment present in a black rabbit is EXACTLY identical to that of a blue; a Chestnut’s pigment is the EXACT same as a Opal, and so on and so forth. Keratinocytes are the cells responsible for growing fur. The colors change as a result of the ability for the keratinocytes to be responsible for pigments, instead of the melanocytes, which are the pigment producing cells. The pigments are in essence transferred from the melanocytes to the keratinocytes.

This is made possible by a protein, myosin 5a (Myo 5a), which transports the pigment granulales. When the dilute mutation is present, the Myo 5a becomes defective. This is what causes the less intense color that the dilute gene is famous for creating.

Extension Locus
The “E” gene codes for a G-protein linked cell surface receptor. Activation of the Melanocortin receptor type I (McR1) by alpha-Melanocyte Stimulating Hormone (MSH) leads to a G-protein cascade. This in turn results in eumelanin production. Agouti Signaling Protein, or ASIP, causes a shift from eumelanin to pheomelanin production. The E locus is like a switch from eumelanin to pheomelanin production, which is “turned on” by MSH and “turned off“ by ASIP. The mutations leading to the inactivation of the E locus have a similar effect of “turning off” the switch, but with a permenant effect. Pheomelanin in this case is continually expressed, giving rise to the orange phenotype.

English Spot Locus
Melanocytes are very closely related to nerve cells, and during embryogenesis, the formation of an embryo, they migrate to where the melanin is found to be produced. A lack of the melanocytes will cause no melanin production, as mutations of the En gene inhibit melanocyte migration. This is caused by cell death, called apoptosis, of the pigment cells. There are many genes involved in exact migration of melanocytes so no two Broken patterned rabbit will have the exact same color spots.