Are you looking to increase your rabbit litter size? There are some strategic methods that you can use to expand your litter size. The majority of traits that play into litter size are invisible and can not be outwardly seen. But, these genetics can be examined through breeding and there are a few phenotypical (physical) traits that are noticeable.
Realizing these characteristics and breeding rabbits that are equipped with them will ultimately increase the size of your litters. Selecting your original breeders, optimizing your feeding regimen, breeding tactics, and starting kit selection soon after kindling will all contribute to increasing rabbit litter size.
Selecting Breeders
The first step towards increasing rabbit litter size is choosing breeders that should produce large litters. There are visible genetic factors (phenotypes) that play into rabbit litter size and invisible genetic factors (genotypes). Finding a breeder who keeps good records and focuses on litter size will be beneficial to the future of your rabbitry.
Original Rabbit Litter Size
The heritability of rabbit litter size is low. Still, kits from large litters tend to produce large litters. So, you should pay some mind to how big the litters are that your breeders come from. You should keep in mind that small breed rabbits generally have small litters (2-5 kits) while large breed rabbits usually have larger litters (8-14 kits).
There are many different genetics that play into conceiving, kindling, and raising large litters. Rather than the original rabbit litter size, you should focus more on how many kits the doe can wean. She may kindle a large litter, but if she can’t raise the majority to weaning then you likely do not want to use those genetics in your breeding program.
Teat Number
Rabbits typically have 8-10 teats. 10 teats are ideal when looking for breeders, both does and bucks. Teat number is more heritable than litter size and “There is a significant correlation between teat number and litter size” (Szendro et al. 744).
“Although rabbits with a higher number of teats do not produce more milk due to the fact that mammary gland size does not depend on teat number, does with more teats have better nursing ability.” (Szendro et al. 744) Does with 10 teats can more effectively feed large litters because there is more nursing availability. Generally, the doe is not in the nest box nursing for very long. So, kits must have the greatest opportunity to drink within this small time frame to maximize the growth and health of the kits.
These does are usually able to wean more kits compared to does with fewer teats. So, one way to increase rabbit litter size is to focus on choosing breeders with 10 teats. “Whenever we select by teat number, doe performance improves.” (Rochambeau et al. 1988).
Conditioning
Both the doe and buck’s conditioning should be examined before breeding. Condition is the amount of flesh covering that your rabbit has. If you can clearly feel the rabbit’s bones it has poor conditioning. If a buck can not sustain his conditioning with proper feeding he is likely to pass on this trait. Therefore, you do not want to keep breeding him.
“In order to reduce kit mortality, doe condition and health status at the time of mating must be examined.” (Szendro et al. 744). Does that are bred while in poor condition may naturally abort some of all of the litter. This is because her body does not have enough nutrients to feed the growing kits. If the doe is at the beginning of the pregnancy she will reabsorb the fetuses, and if she is towards the end of gestation she could birth the underdeveloped kits.
Does typically lose some conditioning throughout gestation. When choosing which breeders to keep in your program you will want to choose does that can sustain their conditioning throughout pregnancy. Connecting with a breeder who pays close attention to their rabbit’s conditioning will be beneficial to your future rabbit litter size.
Feeding Regimen to Increase Rabbit Litter Size
For a doe to raise a large litter, she must be able to supply sufficient nutrients to the growing kits. Even if a large number of eggs are fertilized, the doe’s body can realize that she is not able to support them all. She will then naturally abort some or all of the kits. This is called embryonic mortality and it happens in the early stages of pregnancy. The doe’s body then reabsorbs the barely developed kits.
There is no way for you to outwardly examine embryonic mortality unless the doe quickly loses conditioning or gets sick towards the middle or end of pregnancy. If this happens the doe kits may be too large for the doe to reabsorb and the underdeveloped kits will be birthed.
Nutrient Content Recommendations
You can avoid embryonic mortality with proper feeding. Below are Michigan State University’s rabbit feeding recommendations in terms of nutrient content.
Rations for dry (not lactating) does, herd bucks, and growing young should contain:
- 12 to 15% crude protein
- 2 to 3.5% fat
- 20 to 27% fiber
- 43 to 47% carbohydrates
- 4 to 6.5% ash or mineral
Rations for pregnant and nursing does should contain:
- 16 to 20% crude protein
- 3 to 5.5% fat
- 15 to 20% fiber
- 44 to 50% carbohydrates
- 4.5 to 6.5% ash or mineral
The main nutrients noted on feed bags are protein, fat, and sometimes fiber. So, it will be easiest to focus on these nutrients when searching for feed. MSU also states that it is acceptable to feed rabbits higher levels of protein than what is required for their growing state. Just make sure that the rabbits are not overfed if you will be placing them in your breeding program.
Feeding Amounts
Feeding amounts vary depending on what your rabbits’ diet consists of. Pellets typically have feeding instructions on the bag that correlate feed amounts to rabbit weight and purpose. For example, a buck will be fed less than a pregnant or lactating doe. This is because the doe needs more nutrients to grow and feed kits.
Pellets
A doe’s pellets should be slowly increased when she becomes pregnant. Towards the end of the pregnancy, she should have enough pellets in her feeder that she does not finish them before the next feeding. This is called “free feeding”. You want to continue free feeding as the kits are born and still with the mother.
Once you wean the kits, you should reevaluate the doe’s pellet amount based on her conditioning. If her conditioning is poor she can continue on free-fed pellets until she has sufficient flesh covering. You can then decrease her pellets to the amount your feed recommends based on her weight.
Weight gain usually derives from pellet consumption. Overweight rabbits can create a multitude of issues. The most important when it comes to increasing rabbit litter size is the fact that fat tends to collect around the reproductive organs. Does that are overweight may not be receptive and will likely have small litters if they are receptive. This is because fat collets around the fallopian tubes and reduces the chance of eggs being able to pass through them.
Hay
Hay feeding often becomes controversial in the rabbit world because commercial rabbit pellets are supposed to be a complete feed. Breeders have found success with and without using hay. Some breeders choose not to use hay because it can quickly become messy. The only time they feed hay is if they use it for nesting materials. This encourages the young kits to start eating hard food at a young age. If you feed hay it is usually always free-fed.
Oregon State University mentions in an article, “Hay can supplement rabbit diets, keep rabbits occupied, and help them grind their ever-growing teeth.” (Vanderzanden et al. 1).
Breeders have been successful with many different feeding regimens. Keep in mind, that what works well for one breeder, breed of rabbit, or even location, may not work well for your rabbitry. It is important to learn how to evaluate a rabbit’s conditioning and alter your feeding based on how your rabbits are doing.
Breeding Tactics to Expand Rabbit Litter Size
Some factors play into rabbit litter size when breeding such as how rabbits ovulate, the time of year, and the environment you are breeding in. Rabbits naturally have a high instinct to breed with the seasons so that they are not having kits during the cold months. You can “override” these instincts by adding artificial components or by only choosing rabbits that are receptive constantly to keep in your breeding program.
Ovulation
An article written for Lafeber Vet mentions that rabbits do not have a regular estrus cycle like most mammals. Instead, they are induced ovulators. This means that they are stimulated to ovulate when the buck is riding the doe, and, “Ovulation occurs 10 to 12 hours after mating” (Szendro et al. 741).
Christal Pollock, DVM, DABVP, of Lafeber Vet also states, “If coitus does not occur, the doe will vary in receptivity as ovarian follicles regress and new follicles mature. Periods of receptivity last anywhere from 5 to 14 days and are followed by one to two days in which the doe will refuse to mate. This cycle repeats until conception occurs, although ovarian activity decreases as photoperiod decreases during the late summer to winter months.” (Vella et al. qtd. in Pollock).
*Coitus = mating. Follicle = immature egg located in the ovary before it is released to be fertilized.*
Your breeding practices can increase the chance of more eggs being fertilized. Some breeders choose to breed their does in the morning and again in the afternoon (10-12 hours later) when the doe should be ovulating. Others leave the doe with the buck for approximately a half hour to make sure she receives enough stimulus to ovulate. Christal Pollock, DVM, DABVP, mentions, “A single mating is often sufficient stimulus to stimulate ovulation.” (Pollock).
Time of Year
Photoperiod, or daylight length, plays a role in litter size because rabbits are more receptive with longer daylight hours. “The receptivity and the conception rates are higher in spring because the daylight period is longer.” (Szendro et al. 745). Alternatively, litter sizes and conception rates have been shown to decrease in the fall and winter as the daylight hours shorten.
Therefore, to maximize rabbit litter size, it is best to breed as the days lengthen, but it is still important to keep environmental factors in mind.
Environment
If you live in an area with very hot times during the year this can hurt litter size, both unborn and born. “A lower number of kits is born in summer due to the higher embryonic mortality caused by high temperature.” (Szendro et al. 745).
In other words, high temperatures can cause the doe to naturally abort some or all of the kits at the beginning of development. This is because rabbits typically consume less feed with high temperatures and can not handle growing as many kits with fewer nutrients.
After the doe has kindled she may not be able to produce as much milk as she would in a cooler climate. “Hot climate leads to lower feed consumption and consequently lower milk production and higher suckling mortality.” (Szendro et al. 745).
You can avoid these instances with intentional breeding during cooler times or by adding supplemental cooling methods for your rabbitry. Some breeders have done this by adding shade, fans, or even air conditioning if your rabbits are in a building.
It is also important to add supplemental warming elements if you live in an area with frigid winters and you are breeding during the winter. Overall, rabbits handle cold weather very well. But, small kits are not able to effectively regulate their body temperature since they don’t have fur. It is advantageous to add more bedding to your cages. Some breeders even cover the cage floor when the doe is near kindling. This way if the doe is an inexperienced mother and decides to build her nest outside of the nest box her kits will have a better chance of surviving.
Choosing Kits that Should Increase Rabbit Litter Size
While choosing new breeding prospects to increase rabbit litter size there are a few things that you can notice soon after the kits are born. Sometimes the only available option to increase your rabbitry’s efficiency is keeping back kits that you bred. A helpful tip to maximize rabbitry efficiency is to only keep back kits that outproduce their parents.
Teat Number
“Not only female but male rabbits must be selected. Teat number heritability in rabbits is high.” (Szendro et al. 744). You should evaluate both bucks and does for teat number. Increased teat number (usually 10 teats) allows kits more of an opportunity to drink while nursing.
You can examine teat number right after the kits are born and, “Kits with 10 teats can be marked (e.g. on their ears) to display their teat number when the body is later covered in fur” (Szendro et al. 744).
High Birth Weight
High birth weight has been shown to correlate with doe performance. Kits can be weighed soon after they are born and marked for future breeding prospects. Touching the young kits will not make the mother abandon them. It is important to check your nest boxes because a dead kit can quickly spoil the nest and kill the others. This way you can also make sure they are all being fed.
“The selection of the best does should start at birth. Choosing kits from large litters with birth weight higher than or closest to the average with 10 (or a minimum of 9) teats is advantageous.” (Szendro et al. 745).
Everbreed offers software that makes weight tracking simple and painless. Weights can be entered from your phone and you can later look at Reports to compare doe and kit performance.
Conclusion
To increase rabbit litter size we must think about choosing our original breeders, selecting the correct feeding regimen, optimizing breeding tactics, and beginning kit selection soon after kindling. Choosing quality rabbits to start your rabbitry will be the most influential on your rabbit litter size. But, if you are past this step there are still ways to focus on increasing your rabbit litter size. Everbreed can help you keep accurate records so that you can be efficient in your rabbitry goals.
References
Szendrő, Zs et al. “Management of reproduction on small, medium and large rabbit farms: a review.” Asian-Australasian journal of animal sciences vol. 25,5 (2012): 738-48. doi:10.5713/ajas.2012.12015.
Holcomb, Katie, et al. “Rabbit Tracks: Feeds and Feeding.” MSU Extension, Michigan State University, 2017, https://www.canr.msu.edu/resources/rabbit_tracks_feeds_and_feeding.
Pollock C. Rabbit Reproduction Basics. May 15, 2014. LafeberVet website. Available at https://lafeber.com/vet/rabbit-reproduction-basics/.
Vanderzanden, Elli, et al. “Living on the Land: Raising Rabbits for Meat-Providing Basic Care.” Living on The Land: Raising Rabbits for Meat-Providing Basic Care | OSU Extension Catalog | Oregon State University, Extension & Experiment Station Communications, 1 Mar. 2018, https://catalog.extension.oregonstate.edu/ec1655.
