So you wanna breed rats? An informational guide

writted by MORBID / @rattewy on Discord

So you're thinking of breeding rats?

It's true that rats can make amazing pets, but breeding is a hard job with a lot of things to know and a lot of things that can go wrong.
Rat breeding is not for the faint of heart. You'll be faced with a lot of decisions, hardships, and random health issues; not to mention customers you'll be selling to. There is a major difference between breeding and pet-keeping.
A lot goes into rat breeding and this guide may not even cover it all. There are tons of bits and pieces.
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Use the arrows on the top to navigate through the guide. The other icons will either take you back to the main page, show you resources, or take you to a table of contents.

Common Myths

In the fancy, there are tons of myths and misconceptions. There's also a lot of misinformation out there. Not just for breeding, but also husbandry.
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Statement: Rat breeding is good for profit.
Answer: Not necessarily! Most breeders who make decent profit off breeding are either unethical backyard breeders that breed only for profit or really good breeders that have good, pet-grade rats.
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S: I'm going to breed my rat so I can get mini-versions of him!
A: Not exactly how that works. Offspring aren't exact duplicates of their parents. Certain genes are recessive. You won't get "mini-rats" without a specific pairing. The offspring most likely won't have the same temperament either because it's not 100% genetic. You also don't know what kind of hidden or recessive issues your rat carries.
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S: It's as easy as just putting two rats together.
A: Nope, not at all! You might think that because pet owners deal with accidental litters so often, it would be easy, right? But the reality is that there is a lot that goes into breeding. Most pet owners don't deal with their litters correctly. Just because something doesn't go wrong doesn't mean it can't. As a breeder, you have to figure out who you're going to breed, if you're going to line breed or outcross, or if the doe you want to breed is healthy enough for a litter.

Rat Care & Husbandry

Before you decide to start breeding, you should make sure you have good husbandry and practices. Along with your pet husbandry, you have to pick up a little extra; where will you keep your nursing does?
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Three huge parts of husbandry include enclosures, bedding, and food.
How many cages will you have? What kind? Will you buy commercial cages or will you make your own bin cages? Will you have enough ventilation in your cages? What room will you keep them in? Will it be away from other animals? What will the temp and humidity be?
What bedding will you use? Will you use wood shavings or paper bedding? What about cardboard or hemp? Will you use something with good ammonia control? What nesting material will you use? Will the bedding or nesting material you use pose a danger to neonates?
What food will you use? Will you make your own mix or will you buy a commercial food? How much protein will it have? How much fat? What ingredients will it have? If you use a mix, how will you prevent selective feeding? Are you aware of the symptoms of possible nutritional deficiencies?
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These questions are only the beginning. You also have to consider what you'll have in your birthing cages, how often you'll be breeding, WHO you'll be breeding, etc. How many litters will you breed at once? How old should a rat be before you breed? How much should she weigh? How long will you wait between litters? When will you stop breeding a doe? How often will you line breed? When will you bring in new stock? These are all things you should think about before you start breeding.

Why do you want to breed?

Most breeders have a pretty good reason as to why they want to breed. Breeding is pretty important; you're putting a lot of rats out there into the trade when there's already thousands that don't have homes.
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Most breeders breed with the intention of bettering the pet trade. This can be through supplying pet-grade rats to a specific area (if you have no good breeders around you) or helping standardize certain varieties.
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"Bad" reasons to breed are objective. However, most people consider breeding for money to the one of the worst reasons to breed, mostly because ethically breeding just doesn't bring in a lot of money. For "fun" isn't the best reason either. You shouldn't play with life & death for fun. Rat breeding shouldn't be taken lightly.

Genetics: the Fun and the Bad

Genetics is the study of how certain traits are passed down from parent to offspring. Before breeding, you should familiarize yourself about the basics of genetics, like dominant and recessive genes, alleles, Punnett squares, and more.
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Coat Colors & Markings
Rats come in a variety of colors, shapes, markings, etc. Before you begin breeding, you should know common colors and how genetics works. Learn about different loci, co-dominant traits, lethal genes, etc. Here's a basic run down of rat genetics.
All coat colors are based off of 2 different colors, both controlled by the agouti locus. The two base colors are agouti (dominant) and non-agouti (non-dominant). Non-agouti is black. Then you have dilutes, like red eye dilution, pink eye dilution, mink, etc. You also have genes like pearl, which only shows up on mink. Pearl is a lethal dominant, like silvermane.
Rex and velveteen are co-dominant coat types. This is how you get things like double rex (ReRe, two copies of the rex gene) and double velveteen. Miscellaneous things like dumbo and dwarf are recessive.
This is only the TIP of giant iceberg of rat genetics.
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Hereditary Disease
Cute coat colors aren't the only things that carry down through genetics.
All types of aggression is genetic. It can and will pass down through litters. Tumor rates are also genetic. Rats that have high rates of mammary tumors or cancer will produce rats that also have high rates of tumors or other neoplasms. Cataracts can have genetic factors. Heart disease and obesity can be genetic. Deformations like microtia can be genetic.

Aggression

Aggression, in this scenario, is defined as biting with the intent of biting blood. Of course, this can include aggressive behaviors such as sidling, puffing, etc.
All forms of aggression is genetic. Whether a rat bites out of fear or annoyance? That is determined by genetics.
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Genetic Aggression
Genetic aggression is aggression that shows up at any age in any sex. It's sort of a "catch-all" term, it generally describes aggression. Aggression cannot be trained out. When you're a breeder who's dealing with pure genetics, breeding animals, and customers, you cannot sell aggressive rats. Sometimes it pops up in your lines but it needs to be worked away from. Culling or euthanizing is the best decision for aggressive rats.
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Hormonal Aggression
Hormonal aggression shows up generally at the age of 5 to 9 months in males. Sometimes it'll show up a little earlier, sometimes it'll show up a little later. Hormonal aggression is caused by an increase of hormones (hence the name). Hormonal aggression may be fixed by a neuter, but not always. Bucks with hormonal aggression should not be bred, as it will pass onto pups.
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Maternal Aggression
Maternal aggression occurs when a doe is pregnant or nursing a litter. It may continue even after the litter is weaned. Maternal aggression may be biting you when you come around the litter or killing or attacking pups unnecessarily. Litters born to does with maternal aggression should be culled and the mother should be removed from breeding plans. If the aggression persists, the doe may need to be culled as well.
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Aggression in Breeding
Aggression, again, is genetic. Rats exhibiting any sort of aggression should not be bred. You could be liable for selling aggressive rats; many people have permanent nerve damage from rat bites. Rats can do extensive damage to both people and other rats.

Health Issues

There are a large variety of potential health issues a rat could experience. Some are genetic and some are environmental. Ratguide and Silver's Rattery are both two great sources on medical issues.
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Genetic Health Issues
Like we talked about before, a lot of health issues are genetic. Sometimes health issues are linked to the variety. Protein sensitivity and skin disorders are common in harleys. Marble is prone to teeth issues. Dominant white spotting (sometimes known as high white) can produce rats with megacolon, which most breeders cull for, since it's hard to manage, hard on the rat, and can kill.
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Environmental & Traumatic Health Issues
Respiratory infections can be caused by environment, like low ventilation, draft, or using bedding with low ammonia control. Respiratory infections need antibiotics, but the age of your rats will determine which they need. Doxycycline is commonly used, but will cause stunted growth in rats under 4 to 6 months old.
Traumatic injuries include bites or scratches. These can evolve into abscesses. There are also degloving injuries, commonly on the tail. These all have different manners of treatment.
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Birth & Litter Issues
There are a lot of labor complications that can occur during birth, most of which are dangerous to both the doe and her litter. This includes excessive bleeding, stuck pups, prolonged labor, etc. Sometimes mom will be able to handle it by herself, sometimes she needs immediate veterinary care.
High humidity in the room/cage/bin the litter is kept in may cause ringtail in neonates.

Culling & Why it's Necessary

Culling is the act of humanely euthanizing your stock. This can be done for various reasons. However, it is extremely important to practice.
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Reasons for culling can include...
Failure to Thrive (FTT)
Aggression of any kind
Temperament issues; some breeders may cull incredibly skittish rats
Health issues or deformities
Large litters, as big litters may be harder for mom. Smaller litters tend to produce larger, healthier kits
As a breeder, you'll ultimately decide what you'll want to cull for.
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Why is culling so important?
Culling is very important for health reasons. If you have rats with megacolon or FTT, they will not live. Deformities can be painful and most rats will suffer until they pass. Culling is important for the health of your animals. Culling is also important when it comes to aggression, which cannot be trained out. Pet owners can have whatever view on culling they want, but ultimately it is needed. Breeders need to be prepared to cull and potentially handle passed animals. If you cannot do this, you cannot be a breeder.
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How do breeders cull?
There's a few ways that breeders cull.
When rats are born, they're born underdeveloped. They cannot feel pain or determine temperature. Under 10 days old, neonates can be humanely euthanized via freezer. They can't feel it; it's painless.
CO2 tanks are most common for euthanizing. You will need one if you want to be a breeder, but they tend to be expensive. You need a tank with a regulator. You cannot cull with CO2 without one. Unregulated methods like vinegar and baking soda are highly unethical.
There's also cervical dislocation (CD). It's essentially snapping the neck and is usually used for rats that are older than 10 days but young enough where CO2 isn't that effective. CD should not be performed if you have not been personally trained to do it. If you mess it up, not only is it incredibly painful to the rat, but it will scar you for life.

Money & Financials

Rat breeding is not cheap. There are a lot of things you'll have to spend money on. Estimates aren't always accurate because things can vary a lot. Things you can expect to spend money on include...Static Costs
Cages, including adult cages, growout cages, and nursing/baby cages
Cage accessories
Water bottles & potentially food bowls
CO2 Tank/Setup
Start-up costs for your rattery
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Reoccuring Costs
Bedding, cost/reoccurrence depends on what you use
Food, cost/reoccurence depends on what you buy and if you make it yourself
Getting new rats/stock from other breeders
CO2 canisters
Vet bills. Have a lot saved. As a breeder, you'll have a lot of rats, and you'll have the possibility of encountering birth complications
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These may not be all of the things you can expect to spend money on. Rat breeding rarely draws profit, a lot of the money you make from selling usually goes back into the rattery.

Sourcing your Stock

There are a variety of places you can get your rats from. Finding pet rats are one thing, but finding rats to start your breeding stock with is very different. The most common sources include...
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Pet Stores: Pet stores are one of the most common places you'll find rats for sale. Unfortunately, most pet stores will have sick and aggressive rats. Pet stores don't care about the health of their animals, only the money they get from mass breeding and selling them. Pet store rats have very high rates of health issues like tumors and URIs, not to mention lower life spans. Even if a rat doesn't physically show any issues, it most likely has something hidden genetically. It is highly recommended not to start with pet store stock. However, if you do, you'll need to breed them for at least 5 generations (the more the better) to look for any hidden recessive issues. Get familiar with your rats and your lines before you sell them. Feeder bins are similar, but rats are sold much, much younger and may never be strong or healthy enough to produce a good litter.
Rescues: Rescues are very hit or miss. They tend to be from pet stores or backyard breeders, so they're not all that better (genetic-wise) from going to a pet store. Rescues may also have a lot of health issues that will prevent them from being good breeders. Like pet store rats, if you do choose to breed rescues, you need to breed for at the very least 5 generations to look for any recessive issues. Breeding rescues is highly unrecommended.
Breeders: The word "breeder" means anyone who puts two rats together. Everyone can be a breeder, but not everyone can be a good breeder. It's extremely important to vet all breeders you plan on getting stock from. What are their policies? Are there any health issues that run in their lines? Do they quarantine? Are they okay with you using their stock? Never breed another breeder's rats without permission. This is a good source on breeder red flags & questions, but it's meant for pet owners. It will be a good starting point. A reputable breeder who gives you permission is the best place to start your rattery.
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Generally, you should not breed rats you don't know the background of. But... everyone starts somewhere. You can be breeding for better stock but not selling, and that's okay. You shouldn't be selling rats from lines that you aren't familiar with. It's okay to give your lines time to strengthen.

TL;DR

Rat breeding is hard. It's demanding. You need to do years of research on husbandry, litter planning, genetics, etc. It will cost a lot of money. You will lose your favorite does. You may lose entire litters. You will be faced with hard health issues and aggression. You will be forced to deal with shitty customers. You will have to be okay with culling and you will have to make hard decisions.

So what now?

Do you still want to breed?
Find a mentor. Find someone who can help you through breeding and who can potentially give you stock. Breeding without a mentor will be fairly hard. You should also do a lot of research into husbandry, litter planning, possible health issues, etc.
You can find additional questions here.
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Decided you don't want to breed anymore?
That's okay. It's not for everyone. It takes a lot of time, effort, and money. It's very emotionally and sometimes physically draining.