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4- Feeder Mice :


- Make and Save Money by Breeding Feeder Mice


courtesy to : 

Breeding Feeder Mice


Breeding feeder mice is not only fun and easy but you can make a good profit $$ as well. the pet stores average price for mice is to much, $2.49 each (you should make that profit or savings) . To start a small breeding oporation you'll need 


housing for the mice, 4 containers, 4 


watering bottles, a bag of cider chips or cotton filling , food and don't forget the Mice. (breeding works best when you buy a male and a female, LOL )

Things You'll Need :


  • Housing5gal buckets or glass aquariums something made of hard plastic would be good,walmart sells large plastic containers of all shapes and sizes . Length and depth doesn't mater as much as height, mice are good jumpers, Ive never seen a mouse jump higher than 15" (I use 5gal buckets from home depot). no matter what type of container you use be shure there are no ridges that the little guys can climb up the side.



Vivarium Animals feeding guide

LARGE : Live foods up to or larger than 5 cm or 2 inch in length ..


                            1      >        2

 - Live Birth :

45 deg. Water Bottle

  • Watering bottles For mice it really doesn't mater the size of bottle (I prefer larger = less times refilling) don't fall pray to marketing that says "For Mice" or "For Hamsters"... however the type of bottles you perches is important, the "neck" of the bottle needs to be bent at a 45 degree angle (some times celled "bent neck").

  • Cider Chips Good for bedding, smell removal and Mice toiletpaper (lol) (I've never lost a mouse or had any cider related respiratory problems in the 5 years I've been breeding)

  • But here's another option

  • Cotton filling from walmart i've also found to be easyer to clean up

  • Food Any thing vegetarian. things like grains and starches. Thay love leftovers like speggity (mice will eat around the meat). also cat, dog or bird food.

  • Mice start with only 1 male, and 3 or more females (for each addional female you'll need 1 addional 5 gal bucket )

Housing and Breeding Tips :


First, housing mice. Make a hole in the side of the bucket large enough to fit the water bottle's tip thru, then fill and attach the water bottle. All the females are to be kept in one bucket with some food and cider chips. They will separate or hide there food as the Lady's feel fit, there good at putting things where they wont things and they tend to get bossier when they become moms... Now make a bucket for the male, he's kept separate so that he'll breed when you want him too also some times females can go into heat halfway thru pregnecy (bad for development of babes she currently has and will make her more pregenent also the additional ones will come out preemie) and directly after giving birth, ether way its very hard on there body.

Well i think most people know what to do to get the females to become pregnant, grab a female and put her in with the male leave her for 12 to 15 hrs (if the male has been by himself for a long time it may only take 30Min's lol) . I like to rotate the females IE. day 1 female 1, day 2 no female, day 3 female 2, day 4 no female, day 5 female 3, exec.. I have found that giving him the day in the middle makes him breed more pups per litter (and yes baby mice are called pups).


Now to tell if shes pregnant, if its not obvious hold her across your fingers and lift one finger directly under her belly, wile looking at her back if she looks like she has round marbles on each side of her belly she maybe pregnant. If you think a the mom is pregnant make a new bucket and place her in and add lots of extra food and bedding when she gets close to her due date she will make a nest like bed.


Smells are very important to mice. Never but moms with moms, most of the time if a baby has the the smell of any other mom she will eat the pups. If you need to add one litter to another wash the pups with dish detergent to give them a smell other than there mom. one mom can take care of up to 12 pups and can birth up to 14


When returning mom to the rest of the females you'll need to give her a bath so that the other females wont attack her.


extra info: Pups bite when there eyes start to open, if you handle them for a fue days they'll stop.



So Cute!!! 

Caution Disease :


Hantavirus Concerns:


The Hantavirus pulmonary syndrome is an uncommon but serious disease spread from mice to people when people breathe in dust contaminated by droppings, urine, or saliva from an infected mouse. The disease can also be spread when people touch contaminated objects and then touch their nose or mouth. In many cases of hantavirus syndrome, deer mice have been the carrier. House mice have not been identified as carriers. About a hundred cases have been reported in the Pacific Northwest.


Because of hantavirus, the Centers for Disease Control and Prevention recommend precautions when cleaning up mouse-infested areas. CDC recommends that you wear gloves and wet contaminated areas and dead mice with household detergent or bleach solutions before cleaning them up. Be sure to wash the gloves before removing them. For details, visit the CDC web site.


CDC : 

Don't keep deer mice :



Deer Mice

Even tho there cute too, Don't keep deer mice! If you catch one ware a mask (handkerchief over mouth and nose) and yes you can feed them, even pet them. All ways WASH your hands and anything else that is touched by the deer mice.Description   Color varies greatly with habitat and geographic area. Often grayish to red-dish brown 


above; white below. Tail distinctly bicolor and short haired. 2 forms in eastern part of range: woodland and prairie. Woodland form has much longer tail and larger feet, ears, and body than prairie form.

- How to Breed Mice :


courtesy to :



There are several reasons one would breed mice ranging from a desire to raise them as pets to breeding them as snake food. Whatever the reason for the breeding, there is a specific process for the most humane, safe and effective mouse breeding. Read the following article to learn how to breed mice successfully in your own home.

1- Set up mouse cages in a well-ventilated area.

  • Male mice excrete a musky smell to mark territory, and multiple male mice in the same cage can create a smell that's unpleasant.

2- Place the cages in an area that remains a constant 71 to 86 degrees Fahrenheit (22 to 30 degrees Celsius).

  • Keeping the animals in the improper temperature can inhibit mice breeding or cause the mice to become ill.


3- Place wood shavings on the bottom of your cages.

  • If you want to save money over time, buy these wood shavings in bulk rather than in frequent small quantities from pet stores.

  • Having clean cages that are tailored to the preferences of mice will increase the likelihood of breeding.

4-Purchase mouse food or rodent pellets and a water bottle for each cage. Fresh water should also be supplied every day. In addition to the regular pellets, mice need a well balanced diet that consists of fruit, vegetables, grains and legumes.

  • The right food and plenty of water will help ensure healthy mice, which also increases the likelihood of breeding.

5- Begin to breed mice at a relatively early age.

  • Females can breed from approximately 6 weeks old. Males can breed from approximately 8 weeks old. If time is not an issue, however, it is best to wait until the females are 12 weeks old, as this generally produces stronger litters.

  • Males will generally stop breeding around 1 year old. Stop breeding female mice around 8 months. After that, the likelihood of death in child rearing increases.

6- Determine the sex of each mouse.

  • After approximately 2 weeks, the nipples of female mice should be visible. These will not be visible on male mice. Also, the external genitalia is further from the anus in males.

7- Place 1 male mouse in a cage with several female mice.

  • Generally 2 to 4 females to 1 male works well.

  • Do not place multiple male mice in a cage with the females. The males will fight, often killing each other. The males can also harm the females in the process or the produced offspring.

8- Introduce males and females into a cleaned "neutral" cage at the same time to prevent any issues of territory.

  • While it's uncommon, some males and females will fight if one is introduced into another's territory.

9- Remove the male from the female cage no later than 16 days after introduction into the cage.

10-Wait a minimum of 3 to 4 weeks after weaning a litter before breeding a female mouse again.

Warnings :


  • A female mouse shouldn't give birth to more than 3 litters over a lifetime. Any more breeding events, and the likelihood of serious complications or death is greatly increased.


Things You'll Need:


-Mice (male and female)

-Mouse cages

-Wood chips

-Mouse food or rodent pellets

-Fresh water



Tips :


  • When you breed mice at home, make sure you have multiple cages. This way, you can separate males, females, adults and young as necessary.

  • Over-breeding can result in small litters, unhealthy litters, shortened lifespan of the mother, and/or shortened lifespan of the litter.

  • If a mother is looking a little thin, try feeding some fresh fruits etc. To help her gain healthy weight.

  • If you're purchasing cages from a pet store, make sure your cages are specifically designed for mice and not other rodents such as gerbils or rats. Bars on mice cages are very close together and this will prevent even baby mice from escaping.

  • Never touch the newborns until they can walk on their own, or the mother may instinctively kill them.

  • Put newspaper in cage so she can make a nest.

  • Don't buy rat cages! Mice can escape these.

How To Breed Feeder Mice

Feeder mice breeding

The Guide to Different Frozen Feeder Mice Types :


courtesy to : 


What are different types of frozen feeder mice?


You have probably noticed the many different names exist for feeder mice, such as pinky mice, fuzzies, weanlings, etc. but do you know what each of these names mean, and how they size up against one another? 


At, we offer the freshest, highest quality frozen feeder mice in various sizes. The mice variation you need is dependent on the animal you are feeding. Keep in mind that the different sizes have different nutritional compositions as well. Learn more below about which frozen feeder mouse you should be looking to buy for you snake, lizard or bird of prey. 


Remember this rule of thumb for choosing feeder mice for snakes – choose the size that is just a bit larger than the widest section of your snake’s body. Don’t go too big though, you will risk making the snake regurgitate the mouse if it does not make it all the way down. 


Pinky Mice
X-Small Pinkies: Extra small pinkies are generally one day old and vary in size from .5”- 1” long, not including tail and weigh in at 1.5-1.99 grams. These frozen feeders are called pinkies because they appear pink in color, as they have not formed a coat of hair yet. They are classified as neonatal in the spectrum of nutritional composition. 



Small Pinkies: Not forming their coats yet at 1-2 days old, the small pinkies are pink in color. The small pinkies are the same .5”- 1” length as extra small pinkies, but are heavier in weight, ranging from 2 – 2.49 grams each. . These small pinkies are classified as neonatal in the nutritional composition chart. 


Large Pinkies: These hairless, large pinkies are between .5”- 1” long and weigh between 2.5 grams and 2.99 grams. These large pinky mice are 3-4 days old and also are classified as neonatal. This size is generally the next step up from small pinkies – large pinkies should be fed when the small pinkies no longer form a lump in the snake. This is the last stage a mouse is considered a pinky before reaching fuzzy stage. 

Peach Fuzzies: These peach fuzzies are available in white and dark, without nutritional difference. These particular frozen feeders are between 5 and 9 days of age and grow to be 1” – 1.25”. The weight of this type of juvenile feeder is between 3-4.49 grams. These are perfectly sized for those animals which the pinkies are too small, bit the regular fuzzies are too large. 


Fuzzies: Ten to thirteen days of age, these juvenile fuzzies have developed a full coat of hair (unless they are the hairless breed). The fuzzies are slightly larger at 4.50 - 6.99 grams a piece, and are between 1.25” and 1.5” long, not including tails. Fuzzies have developed eyes, but they have not opened yet. Fuzzies come with hair or hairless, so make sure to order the one your animal is used to. 


Adult Feeder Mice
Hoppers: Hoppers are within 14-18 days old with fully open eyes. They are starting to eat and drink on their own at this point and range between juvenile and adult, depending on the grams, which generally the hoppers fall between 7.00 and 12.99 grams. The length of these fresh-frozen feeders, not including tails, is between 1.5” and 2”. White hoppers, dark hoppers and hairless hoppers are all available for purchase and animal consumption. 


Weanlings: By 21-25 days of age, these weanlings eat and drink on their open, have their eyes open and have developed a full coat (aside from hairless weanlings). They are classified as adults at this point and are available in white weanlings, dark weanlings and hairless. They have bodies around 2”- 2.5” long and weigh between 13 and 17.99 grams. 


Large Adults: Feeder mice are classified as large adults once they hit sexual maturity around 30-40 days old. These feeders include: white adult mice, dark adult mice and hairless large mice. As they are 30-40 days old, their bodies are around 2.5”- 3” long and weigh between 18 and 24.99 grams. 

X-Large Adults: These feeders include: white adult mice, dark adult mice and hairless extra-large mice. The XL adult feeder mice are obviously the largest mice product offered. They reach 25-45+ grams each, and reach a body length of 3”-3.75”. carries all of the above frozen feeder mice. If you need help choosing the correct size and age of your feeder rodent, contact us and one of our experts can assist you in your selection.



5- Feeder Rat : 


Small Scale Rat Breeding


courtey to : 




I strongly believe in responsible ownership of all animals, including feeders. So whether you decide to feed live, pre killed or FT, know all the dangers involved with each method and properly ready yourself for any and all mistakes, the care of, or exceptions.


This method is ONLY good for a snake that eats Frozen Thawed prey.
This method is NOT for snakes that will only eat LIVE prey.

“Should I breed, how many to breed?”

5 snakes means 5 rats per week * 26 weeks (6 months) = 130 rats total

To buy at the pet store : 130 rats * $4 per rat = $520 avg. for 6 months.

To buy F/T from a .com : 130 rats * $0.92 per rat = $120 for 6 months.


Avg. $0.69 each rat + $0.23  ($0.23 is what is costs to ship each rat total = $30)

Initial Setup Cost : $368 - $428 for first 6 months. 
Then $222 - $282 for following 6 months. Close, but not really worth it. And, this doesn't factor in time, smell and frustration!


  • $146 for rats: I assumed 12 breeder females (to produce 10 feeders per week) and 2 males * $4 per rat = $56 (one time cost)

  • + Monthly Food/Bedding: = $37-$47 * 6 month = $222 - $282

  • and you have to buy/build housing for all of them = $100?? (not factored in to final cost)

  • You want to breed your own feeders

  • You have 1 snake

  • But you don’t want to be over run with rats either



    If you have 1 snake, I still recommend either buying bulk F/T from online suppliers. This is not only economical, but saves you a lot of time, smell and frustration.


Cost to Raise Your Own Feeders- Is it worth it?


As always when embarking on a new project, the first thing to outline is the COST, and it's no different here. Some of you may not care the cost and are interested solely in raising quality rats to feed your animals and that is understandable, but it's always nice to see a little bit of math and how much everything adds up.


Below is a short excerpt based on a topic from the forum by Sean (aka, Lord Jackel). It outlines the general costs for raising rats to feed 5 snakes for 6 months.


Note 4/25/15 - These costs represented below are from 2007. The cost of rat food has risen considerably, and we have not done a review to update for current costs.

If your snake only eats live, I do not recommend this. 

Breeding Age and Weight :


-Female rats are able to breed sometimes as early as 5 weeks, however it doesn't guarantee a high number per litter. For those reasons, I go by the rule of  "5 Months, or 250+ Grams". Once a female has reached either of these two markers, I consider her to be able and ready to breed. Considering how much time it takes to raise a female rat, or to choose females I believe will improve or maintain high production in my colony, I do not want to lose a female rat because of simple impatience.


Being kept on the schedule in this article, my females have shown to produce good sized, healthy and chubby litters up to and over 15 months, even if it is a small litter near the end; and females will gradually produce smaller litters as they age. Once they reach the 15-17 month mark, I will retire them to baby sitting duty for grow up females or weaners. They do a good job of socializing with the younger girls.


**It should also be noted that any females that have a poor  experience (extended hard birth, cannibalize litter for any reason after many successful litters, poor health after weaned) she is evaluated and it is decided whether to retire with good quality of life, or if it would be more humane to put her down.


-Males are fertile between 6 and 7 weeks of age, however, many females will not allow a male of that size and age to breed with her. It may be because she does not recognize him as a suitable or desirable mate. For that reason, I will wait to breed my males until they are near or over 300+ grams. You can certainly put them together as soon as you think is adequate, but realize that you may not get litters very quickly, especially if the females are seasoned and large breeders.

Minimum Rat Breeding Group :


At the very minimum, I recommend buying 4 young rats. 2 males, 2 females. They MUST be separated by sex!!!


٭Rats are social animals and need to have a partner at all times! Rats appear to suffer negative effects when not with a partner. For their physical and mental health, they need to be with other rats.


With this set up, you can use either a rack (link to DIY for RACK) or tubs (link to DIY for TUBS), given they are big enough for adult rats to live in comfortably.

You’ll need at least 3 different spaces for these animals. (Maybe 5, if you need to raise up rats)




  • 2 large tubs for the nursing mothers

  • 1 large tub or cage for the males while not breeding females

  • Optional **2 tubs for any weaners that you need to grow up to a larger size (one for each sex)

  • CO2 Chamber, or have a source for dry ice to gas with CO2. Dry ice can be found at stores like Walmart or Krogers. I do not recommend any other form of euthanasia. (click here to go to my humane euthanasia article)

**If you plan on just feeding weaners, you can CO2 the animal at 4 weeks of age. They should weigh anywhere from 60-80 grams avg. This means you wouldn't need the 2 holding tubs.


Breeding Process:



Once the females reach 5 months of age, or 250+ grams, they are old enough and big enough to breed with minimal risk. If you’ve taken the time to buy young rats and socialized them, you’ll have a much easier time dealing with the mothers and her young when cleaning or moving. 


Day 1 - Pair up one male and one female into each tub. Both females are being bred at the same time.

Week 1 (day 7)- Check on the little love birds!
Week 2 (day 14)- Is momma getting big yet?
Week 3 (day 21)- After the 3 weeks, you will remove the males from the tubs and put them into one large tub/cage to keep each other company. Females go into their own tub by themselves to birth.

Week 4- Both mothers should have plenty of nesting material. Shredded aspen works very well. They should have their litters during this 4th week.

Week 6 - You can put the females together to nurse both litters, the pups are old enough now that they should all be strong enough to each get their fair share of milk.

Week 8- The pups will be weaners and need to be removed from the mothers, separated by sex to grow up, or be euthanized with CO2.


With this process, your 2 females will have anywhere from 9-16 pups average. You can CO2 the litter, and you’ll have 18 - 32 weeks worth of food in your freezer for 1 snake.


Prepare ahead of time and give yourself at least 2 months in advance to produce more weaners.



Humane Euthanasia for Rats :


I am writing this small section to direct you to my Humane Euthanasia article that outlines the socially and humanely acceptable methods for euthanizing your rats. 


Humane Euthanasia for Rodents


I do not support other methods, I understand some commonly practiced methods may be approved by the AVMA, but only for qualified and supervised professionals in a controlled environment.  I feel that the margin of error is too large to promote with good conscience regardless of the condoning by the AVMA.


eeders or not, they deserve respect. Without them, you would not be able to keep your snake.



I attempted to do some math, to see what you’re really spending on raising rats rather than ordering FT online. (I rounded up just to cover any incidents and averages from my own colony)

Note 4/25/15 - These costs represented below are from 2007. The cost of rat food has risen considerably, and we have not done a review to update for current costs.

Raising 4 adult rats to feed 1 snake:


4 rats to feed
.83 lbs ea wk /rat
3.32 lbs eaten /week
13.28 lbs /month
50 lbs /bag
3.77 months/ 50 lbs bag
3.18 bags /year
$25 * 3.18 bags = $79.50 /year


Bedding Pellets
40 lbs /bag
3 scoops /tub
36 scoops /bag
12 tub changes /bag
5 tubs /week
2.4 weeks /bag
21.67 bags /year * $6 = $130.02 /year


Raising your own feeders
$209.52 /year


Aspen l x w x h (Aspen is cheap and has been given very generously. This is an optional number)
4 cubic feet /bag
.083 cubic feet /tub (12″ x 6″ x 2″)
.42 cubic feet /week (for 5 tubs)
9.5 weeks /bag
2.4 months /bag
5 bags /year * $12 = $60 /year

Raising your own feeders w/ lots of aspen
$269.52 /year

Buying FT Bulk online
.99 each small rat
20 /bag
2.6 bags /year
$51.48 /year FOR 1 SNAKE
$38.16 shipping /box

$38.16 * 2 (for shipping once every 6 months) = $76.32 shipping /year

Now compare!!!

Buying Bulk online:
$127.80 /year


Raising your own feeders:
$269.52 /year

Videos : 

Breeding rats for snake food

Breeding Snake Food

Super easy rat breeding setup 


Rat Breeding Facility

Rodent Breeding Colony Management – Rats


courtesy to :

Boston University is committed to observing Federal policies and regulations and AAALAC International standards and guidelines for the humane care and use of animals. This policy provides guidelines for rat breeding colonies.


Rats have short gestation times, with litter size varying from 8 – 16 pups. Therefore, cages may quickly become overcrowded if the individual responsible for managing the breeding colony and separating animals at the proper times does not do so in a timely fashion. When this happens, the animals become uncomfortable and stressed. Pups can die from being trampled. In static micro barrier cages the air quality quickly deteriorates with a high density of animals and may predispose them to respiratory disease.


In addition, rats grow throughout their lives, and may reach a body weight of 500 g or more. Rats also grow quickly, such that regular monitoring is needed to keep the cage from becoming too crowded. Overcrowding of cages is an animal welfare concern and can have a deleterious effect on research.




To define standards and responsibilities for rat housing and rat breeding cages and to assign responsibility for action when rat breeding cages become overcrowded.


A. Investigators are responsible for:
1. Coordinating with LASC/LACF for space allocation for their rat breeding colonies.
2. Managing their own breeding colonies unless arrangements for technical support have been made with LASC/LACF.
3. Designating a Colony Manager (someone who has received specific training on managing rat breeding colonies, and who will be the primary contact person for the lab). More than one Colony Manager may be designated by the PI, but it is preferable that this number be minimized to facilitate communication between LASC/LACF and the rat users.
B. Designated Colony Manager (research staff or LASC/LACF staff) is responsible for separating animals according to allowed cage space as described in III, V, and VI.
C. Both the LASC/LACF staff and investigators managing their own rat breeding colonies must abide by the procedures outlined in this document.
D. Any recurring problems with rat breeding colony management will be brought to the attention of the IACUC.



Two different breeding schemes are acceptable. In either case, the Designated Colony Manager (research staff or LASC/LACF staff) is responsible for carefully monitoring pregnancies.
A. Monogamous pairs
Postpartum estrus occurs within 24 hours of parturition; thus if a male is left in the cage, the female is likely to become pregnant again while lactating and nursing the new litter.
1. Male is removed AFTER the litter is born.
One male (ONLY ONE MALE PER CAGE IS ALLOWED) and one female are housed together for mating. Nesting material is provided in the cage. The rats are not separated when the female becomes pregnant or delivers the pups. To provide more space for the pups, the male is removed at first cage change after parturition. This model takes advantage of postpartum estrus and allows the female to become pregnant and nurse at the same time. Litters are born approximately 21 days apart. The 3-week old litter must be weaned prior to the birth of the new litter.
2. Male is removed BEFORE the litter is born
One male (ONLY ONE MALE PER CAGE IS ALLOWED) and one female are housed together for mating. Nesting material is provided in the cage. When the female is noticeably pregnant the male is removed from the cage.
B. Harem mating
This method houses two (2) females in a cage with one male (ONLY ONE MALE AND TWO FEMALES PER CAGE IS PERMITTED).
During routine health/breeding checks, each noticeably pregnant female is removed and placed in her own cage. When the pregnant female is separated from the harem cage, she is given nesting material in her delivery cage to make a nest for her pups. Female delivers her pups and nurses them for 21 (or up to 28 days, with LASC/LACF approval, following the procedure below in V.A.1.). Only one nursing female and litter is allowed per cage. After the pups are weaned, the female may be returned to a harem cage.
C. The Designated Colony Manager has primary responsibility for checking for pregnancy and birth and for recording these events on the cage card(s). When the litter is born, the cage is flagged with a New Litter card and the Date of Birth (DOB) and projected weaning date are documented (See IV.C.) However, if LASC/LACF staff finds births of litters when checking and changing cages, they will place a new litter card and DOB.
D. After pups are born, the cage is left undisturbed for at least three (3) days except for replenishing of food and water as needed. In case the bedding gets very dirty or wet and the cage must be changed sooner, the following procedure will be followed. The female is transferred first, and then the litter plus a small amount of the dirty bedding (so the smell in the new cage will be familiar) is scooped up altogether with a gloved hand and transferred to the new cage. The same procedure is followed until the pups start moving around the entire cage.



Investigators may use LASC/LACF cage cards as described below, or cage cards of their own design, as long as the information listed below is available.


LASC/LACF cage cards


A. Cage card
Required information:
• Principal Investigator (name)
• Account # (when required)
• IACUC protocol (ID#)
• User name/Colony Manager
• Contact information
• Species
• Strain or stock and specific GEM or mutant nomenclature
• Vendor (“in-house” for animals bred in-house)
• Number of animals and sex
• Date of birth (DOB)
• Date of arrival*
*Not always applicable

B. Breeding card
Required information:
• Principal Investigator (name)
• IACUC protocol (ID#)
• User
• Contact information
• Litters born and DOB



C. New litter card (so that it is visible, this card is placed vertically behind the cage card)
• Date of Birth (DOB)
• Projected weaning date of new litter



A. Age of pups at weaning


Weaning age for rat pups is routinely 21 days of age. In the case of some inbred, genetically modified or mutant strains, it may be advantageous to allow the pups to remain with the female for 28 days.
1. To extend nursing time past the 21 day standard, LASC/LACF must be notified by placing a note on the New Litter card. The Colony Manager must communicate via email to or when all pups in a given breeding line will be routinely weaned at 28 days.
2. User writes “Extended Weaning”, “Date to wean” and “Dam (Mother) not pregnant” on the cage card.
3. Allowing a 3 week old litter to stay in the cage with a lactating female that also has a newborn litter is not permitted.


B. Monogamous pairs


Assuming the lactating mother is pregnant, pups are weaned at 20-21 days of age, just before the new litter is born. This will prevent trampling of newborn pups by the weanling pups, and prevent the cage from being overcrowded.


C. Harem mated females
If a singly housed lactating female is alone in a cage with her litter, weaning is less urgent then with monogamous pairs. However, rat pups are routinely weaned at 21 days of age unless an exception has been approved by the IACUC and LASC/LACF (See V.A.1. above).

D. Separation of sexes at weaning


1. Male and female pups are separated at the time of weaning, rats of each sex being placed in a separate cage.
2. If a litter contains only one pup of a given sex, provisions must be made to house this pup with others of the same sex. Newly weaned pups must not be housed singly. Possible housing options include:
a. A single female pup may be housed with the mother.
b. A single male pup may be placed with other male pups from a different litter of the same age.
c. If the parents are a monogamous pair, a single male pup may be housed with the father, both being separated out into a new cage.
d. A single male pup may be housed with female sibs up to six weeks of age (i.e., adulthood, V.A.1).
e. More than one male pup may NOT be housed with female sibs.
f. It is recommended that sexing of the pups be verified one week later.

E. Feeding of weaned pups


At the time of weaning, a small amount of chow (only a few pellets so they don’t get moldy) must be provided on the cage floor for the next seven (7) days.




Rats are social animals and because male rats rarely fight, with the notable exception of retired breeders, every effort must be made to group-house rats whenever it does not interfere with the experimental design. Post-operative rats may or may not be group-housed, again depending on their postoperative needs and the experimental design.
Cage sizes may vary in different facilities. The Colony Manager is encouraged to ask LASC/LACF staff for information on the size of cages in which their rats are housed.


A. Static rat cages with filter tops and an inside floor area of 170 square inches OR Individually ventilated cages (IVC) with filter tops and an inside floor area of 160 square inches.

1. One adult female rat with one nursing litter are allowed per cage

2. One retired male breeder per cage

3. Eight (8) young rats up to 100 gm per cage.

4. Six (6) rats weighing up to 200 gm each per cage.

5. Four (4) rats weighing up to 300 g each per cage.

6. Three (3) rats weighing up to 400 g each per cage.

7. Two (2) rats weighing up to 500 g each per cage.

8. Rats over 500 g may be singly housed, or may be pair-housed, as determined by the PI and approved by the veterinarian and IACUC.



A. The Designated Colony Manager (research staff or LASC/LACF staff) is responsible for cage card documentation and for separating and weaning according to the above guidelines


B. Non-breeding experimental rats are separated as needed by the PI or research staff, unless technical support has been arranged with LACF/LASC in advance.



A. The LASC/LACF Staff checks for O/C and pregnancy when performing daily health checks and when changing cages. Any cages that are overcrowded according to the standards defined above are marked with a Problem Notification – O/C card, dated and initialed.


B. When overcrowding is noted, the responsible individual, the Designated Colony Manager, is contacted via email and is given 48 hours to correct the problem, depending on the severity of the overcrowding NOTE: WEEKENDS AND HOLIDAYS COUNT AS DAYS AND ARE NOT EXEMPT.


C. If overcrowding is not addressed within the allotted time, LASC/LACF staff separates the rats and charges the PI.


D. When two litters, one newborn and one previous litter, are in one cage separation is performed as soon as possible. In such a case, the LASC/LACF Staff separates the older pups into a separate cage and provides food on the cage floor. Female and new pups are left in the breeding cage. Cage is marked with a Problem Notification – O/C card (and any other information necessary to identify the rodents), dated and initialed and Colony Manager is notified via email.


E. Any time a cage is significantly overcrowded and the welfare of the animals is at stake (Emergency O/C), the animals are promptly separated into acceptable group sizes and Colony Manager is notified via email.


G. When the overcrowding is corrected the O/C card is removed.


References :


1. The Guide for the Care and Use of Laboratory Animals. 1996. NRC ILAR. P.27. Table 2.1. Recommended Space for Commonly Used Group-Housed Laboratory Rodents.
2. LASC and LACF Standard Operating Procedures (SOPs).
3. UMDNJ New Jersey Medical School Comparative Medicine Resources Rodent Breeding Policy and Standard Operating Procedures (SOPs).

Videos : Sample of Rat Brreding projects :

Rat Breeding Project

Rat breeding project update​

LARGE : Live foods up to or larger than 5 cm or 2 inch in length ..


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