Orphan Bunnies, Fostering, and Bottle-Raising Kits

This is a follow-up article to the one posted previously, "Are My Kits Getting Enough Milk?"   Please check out that article first if you haven't already, as it will walk you through a process of determining if a litter needs some human intervention and how to evaluate belly-fill in kits.  The article can be found here http://blossomacresrabbitry.blogspot.com/2020/10/are-my-kits-getting-enough-milk.html.  Most breeders eventually end up in a situation of baby rabbit kits that need additional assistance or full care to survive.  It could be due to a doe not producing enough milk, a first-time mom not caring adequately for her kits, too much competition with a large litter size, the mother passing, or a number of other reasons.  I have artificially reared quite a few kits from birth to weaning and have learned a lot over the past eleven years of raising rabbits that I hope will be helpful to others.

"Did somebody say milk?"

I would like to emphasize that artificially rearing a kit should be a last resort if all the other methods fail.  Rabbit kits are very delicate and extremely difficult to hand raise.  Raising kits on rabbit milk is by far the best option for them, so I will outline some ways to try to do this before resorting to artificial rearing.

IS THERE ENOUGH MILK IN THE RABBITRY?
This may sound like a funny question, but remember that natural rabbit milk is by far the best option for a kit, so very important to explore before resorting to other milks.  Does the mother herself have milk, but some other issue is causing her not to nurse her kits?  Does another doe in the rabbitry have additional milk (maybe she has a smaller litter size and plenty of milk to go around or she may have lost kits of her own)?  Do you know anyone else who has a doe at a similar day in lactation?  If you answered yes to any of those scenarios, that is an excellent avenue to explore and we will discuss how to take advantage of this option to nourish kits that need it.  If not, more suggestions are further into this article! 

FOSTERING KITS
If you have another doe that is producing milk well and does not have a particularly large litter/her own kits are thriving, she may be able to support more kits as well.  This is often called "fostering" or "grafting" and is sometimes the easiest option and can be as simple as placing the hungry kit(s) into the nest of another doe for her to nurse along with her own young.  Fostering can be done with newborns or slightly older kits, but becomes significantly more difficult with age as the foster doe is more likely to reject an older kit.  Ideally, the litters you are combining will be of a similar age and size, although a few days difference can still be successful.  Some does are very aware of the smells of their nest and quick to reject an invader while others do not seem to know or mind and willingly nurse other kits.  While somewhat opposite, both of these are positive maternal traits (being protective of her own kits or nurturing to all).  I tend to aim for "tricking" a doe so to speak by slipping in another newborn shortly after she has given birth so that she does not know one of the kits is not hers.  Although not always necessary, I also try to keep the other doe's scent from being a potential problem since some rabbits are very territorial.  Clean off any of the mother's plucked hair from the kits you are trying to foster.  Next, gently rub the kit with the other kits and fur in the nest to put their scent on it.  Since the mothers tend to check their nest shortly after I handle it, I also cover the kit with the other kits and fur so that there is not an obviously new sight and smell on top of the nest.  For some foster mothers, you can also put a dab of vanilla extract on their nose which seems to distract them from the new scents in their nest.  I will then keep a careful watch of the nest to make sure that the foster mother accepts them and check them twice a day for several days at first to make sure they are eating well along with the rest of the litter.  

One question that often comes up in fostering situations is how to tell kits of the same color and different litters apart.  Whenever possible, I will try to arrange it so that there are not two kits of the same color and different pedigree in the same nest box.  If that is not possible, you can put a small dot in the ear of each fostered kit in question with a sharpie marker and make sure to re-do the mark regularly as it fades quickly.  Some breeders will also tattoo a dot in the ear of a fostered kit for permanent identification.  When fostering, keep good records!  You do not want to be second guessing the pedigree/genetics of a litter down the road. 

ASSISTED NURSING
If the biological mother herself has milk but is not nursing her litter for whatever reason or you have other does with milk that you are unable to graft kits onto (their litter may be too old or she may have rejected a graft attempt), "assisted nursing" is an excellent option.  Keep in mind, however, that a doe's milk starts out very rich at early lactation and gets gradually less rich further into lactation, so try to feed kits on a doe that gave birth at a similar time.  There are two main methods of doing this and I find the first method to be more successful.

Method #1  With this method, the kits are nursing in the most natural way possible.  First, place all the kits in the center of the nest and remove the extra hair or bedding that make it harder for them move about.  Next, very carefully, lower the lactating doe into the box in a standing position directly over the kits.  Some does will happily feed the kits at this point, but chances are, she will try to leave the box.  It is important to hold the doe still and keep her from jumping out, rotating in the box, stomping her feet, hurting the kits, or preventing them from nursing.  You want the doe to be standing lightly on her feet so there is a gap under her belly for the kits to nurse.  A rambunctious doe will usually quiet down after a minute or two, but it is important to still gently hold her.  Feeding with this method usually takes about 5 minutes and the kits can be faintly heard nursing so you know they are busy.  If this attempt fails for whatever reason, you can try again with another doe if available, but should give the kits a rest before trying again.  Kits get exhausted after trying to nurse and not getting an adequate meal and will often temporarily stop trying after a failed attempt.  

This is my go-to method as it works extremely well and the kits' bellies fill fast.  If a first time mom is not feeding her kits enough, but has plenty of milk, feeding the kits on her like this a few times can help her instinct to kick in and she may care for them thereafter.  Some signs I look for that show the doe is learning to care for them herself is she will stay in the box without me holding her and will arch her back to allow the kits to nurse easily below her.  She will also put her head down to groom the kits.  When this happens, I can usually put the nesting box back with the doe and she raises them perfectly thereafter.  

Method #2 of assisted nursing is one that you may read about more often, but I find to be more difficult and less successful in practice.  This method involves laying the doe on her back and gently restraining her while the kits are placed on top of her belly to nurse.  It takes much longer for the kits' bellies to fill when they are nursing upside down like this and they sometimes get exhausted from trying.  The doe's milk does not "come down" well when she is upside down and kits normally nurse upwards, so this is unnatural for them.  There can be difficulty with the kits scurrying around on the doe's belly and falling off your lap and the doe can (and often does try to) give powerful kicks with her hind legs that can potentially injure the kits.  For these reasons, I much prefer the first method, but still carefully use this method if needed.

 

ARTIFICIAL REARING AND SUPPLEMENTING

 

If the above options failed or are not available, supplementing or artificial rearing is the next best option.  I want to emphasize that artificial rearing does not have to last until weaning.  If attempts at nursing kits on natural rabbit milk failed one day, a meal of other milk can be used to get them by one more day before trying again on natural rabbit milk.  This is known as supplementing rather than artificial rearing.  Sometimes the does just need a little longer for their milk production to kick in or the kits just need a little more strength to nurse well later.  It is better for the kits to have a few days on other milk than to be reared entirely artificially.   

 

Rabbit milk cannot be compared nutritionally to other readily available species' milk like cows and goats because it significantly richer.  Rabbit milk is much higher in fat and protein than cow milk and the lactose content is extremely low.  Because of this, you need to be very careful that you are offering the kit something as close as possible to what it needs nutritionally.  Compare rabbit milk with the other milks below.  A kit would starve on average cow milk alone.  I often seen goat milk recommended as a substitute since it is higher fat than cow milk, but goat milk also does not come anywhere close to rabbit milk.  Kitten milk replacer is also not rich enough for rabbit kits.

g/100g	Cow	Goat	Sheep	Rabbit
Fat	3.7	4.3	6.1	12.9
Protein	3.4	2.4	4.7	12.3
Lactose	4.1	3.7	4.8	<2
Keszcka et al. 2013, Balthazar et al. 2017, Maertens et al. 2006

With this in mind, I recommend a special milk replacer that is high in fat and protein.  Fox Valley makes one for wild rabbits (32/40) which can be found here https://www.squirrelsandmore.com/products/fox-valley-32-40-squirrels-opossums-and-bunnies.  Some prefer Fox Valley's 30/50 formula and that can be found here https://www.squirrelsandmore.com/collections/milk-replacers/products/fox-valley-30-50-beaver.  I would recommend keeping a bag on hand and it can be frozen after opening to keep fresh. 

There are certainly other options too, especially in a pinch, but they are more difficult to balance.  Cream can be added to milks to increase the fat content and egg yolk or a high-protein colostrum powder can be added to increase protein.  Evaporated milk also offers higher protein and fat than whole milk because it is concentrated, but still needs additives to balance it closer to rabbit milk.  I have successfully weaned quite a few kits from birth over the years using several different types of milk with careful consideration that they are getting enough fat and protein in particular.     

Here is a recipe of mine that uses a goat milk base if you cannot get the rabbit milk replacer.  It has too much lactose because it is goat milk, but comes much closer to rabbit milk in protein and fat than most recipes I have seen.  I am not a nutritionist and it isn't perfect, but significantly closer than most others I have evaluated.  It is important to use the brands I listed for these items because they all are different and I balanced this recipe to these brands.  I would also provide the kits with water and teach them to drink from a bottle by 2 weeks of age.  You can scale the recipe up or down as needed.     

5 tablespoons evaporated goat milk (Meyenberg evaporated goat milk)

1 tablespoon colostrum powder (Lifeline Rescue Lamb and Kid Colostrum Replacer)

1 tablespoon heavy whipping cream (5g fat per 15mls)

"BOTTLE" FEEDING
Different methods of artificial rearing are often lumped into the term "bottle feeding" even when no bottle is involved.  The younger the kit is, the harder it is to artificially rear.  If at all possible, try to get the kit through the first few days by feeding on other does (even if their milk production is low) because it is extremely difficult to feed a newborn.  This also allows for consumption of colostrum.  Even just two days makes the job significantly easier.  

The first thing you are going to need is a tool to feed them with.  I find that actual bottles (like what you can find sold for newborn kittens or multi-species use for wild animal babies) do not work.  The nipples on them are too firm for a newborn kit and are often too large as well.  My go-to tools are either a small glass eye dropper, or a small syringe with a tip meant for slip tip needles.  Luer lock syringes do not work without cutting off the lock feature.  I like using syringes because I can see exactly how much milk the kit is getting.

 This shows the kind of tip you want on a syringe for bottle feeding a kit.  I like to use between 1 and 5 cc syringes for this.  Glass eye droppers are also good for bottle feeding.  

 This syringe has a Luer Lock tip which is difficult to use for feeding kits because the locking feature shields the tip.

 

Some people report success using "Miracle Nipples" in the mini size, but I find these do not work well with newborns because they do not have a strong enough suckle.  These may work better with older kits that are used to them.  The benefit with these compared to a standard bottle and nipple is the ability to attach them to a syringe.

Besides your milk and feeding instrument, you will also want to have some highly absorbent material to use for cleaning the kit's face.  Early on with bottle feeding, the kits tend to fight you quite a bit and spit out the milk, so have lots on hand.  You do not want any milk getting in the kit's nose.   You need material that can soak up a stray drop of milk really fast, so a washcloth or other cloth do not work as well as paper towels.  

Once you have everything ready, you can begin feeding the kit.  Bottle-raised kits get super friendly and very easy to feed when they are older, but are much the opposite at first.  Expect the kit to fight you quite a bit and the feeding time can take an hour or more, requiring a lot of patience.  It is very important to prevent aspiration while feeding.  Begin by placing the eye dropper or syringe tip in the side of the kit's mouth and put a tiny drop of milk on the tongue.  If possible, try to keep the tip in the mouth between each drop and make sure it swallows each time.  When a kit is not swallowing well, try taking the dropper out of the kit's mouth and than putting it back in as though you are going to give it another drop.  They usually swallow after doing this and then you can continue giving them a drop at a time.  With time, it gets easier and you can give them a very slow and steady stream of milk rather than a drop at a time. You will still have to put the tip in the kit's mouth, but they will nurse more willingly on their own.  Eventually, they will run up to you and take it willingly by themselves and then feeding them can take just a couple of minutes.  As for how much to feed them, I always go by the "toad belly" look and base it completely on how big the belly is at the time.  They do not have to have a giant belly like some kits do, but you do want to see a definite roundness and fullness to them.  This usually ends up being 2-3 mls of milk per feeding for younger kits, but the roundness of the belly is more important than measuring milk since a lot of milk is wasted while feeding.  

"Bottle" Feeding a Kit with a Syringe

 

 This kit is about 2 weeks old and nursing quite aggressively.  Kits tend to make a mess when nursing this way, but at this age, they can groom themselves and are less prone to aspiration.  With younger kits, I feed much slower and quickly absorb stray drops of milk as they are unable to moderate this themselves.

TUBE FEEDING

Esophageal tube feeding is another technique for feeding kits, but requires training on insertion technique from someone experienced.  This method is safer if done correctly, especially for newborn kits, as the milk is delivered directly to the stomach rather than to the mouth where there are more opportunities for aspiration.  The possible error with this method is if the tube is inserted incorrectly down the trachea (windpipe) rather than the esophagus, so very important to learn proper technique.  You also do not want to feed with this method longer than needed as it can cause esophageal irritation.   

 

 

FEEDING FREQUENCY AND WEANING

Kits should be fed twice a day depending on how well they eat and how full they look following a feeding.   I find that once-daily feeding is often not enough unless the kits get very full bellies at the first feeding.  In the first few days, I measure that I give kits about 3ml a feeding, but that also includes some waste that they spit out.  It is better to gauge milk consumption on the roundness of the belly than how much was measured at feeding.  As they get older and start sampling pellets and drinking water, you can gradually cut back on how much milk they are getting.  When to wean bottle babies depends a lot on how strong they are and how well they are growing.  Very difficult eaters can sometimes be weaned at 4 weeks, but I try to go a full six weeks if possible.  Some kits that are not growing well need more than that and I weaned one doe at almost 10 weeks once because she needed the extra care.  

HUSBANDRY OF ARTIFICIALLY-REARED KITS

Nest - Kits ideally should be kept in a natural nest consisting of bedding such as hay or straw and rabbit fur either that their mother plucked while kindling or fur from another rabbit (saved while grooming).  Fur should be short to prevent it wrapping around the kits' necks or legs and cutting off circulation and can be trimmed if needed.  The nest should have a rough surface on the floor to prevent kits from burrowing down and slipping on the bottom.  Wet/soiled nest material should be removed regularly.  The nest is especially important in the first 2 weeks of life.  Kits are more likely to start exploring and leaving the nest at about 2 weeks of age, so keep the nest somewhere that contains escapees!  

   

Warmth - Do not use an electric heating pad under the nest!  Even at a low setting, they are too hot and excessive heat will cause the kits to scatter away from each other in the nest.  Even in a cool environment, kits should be able to stay warm in their nest without any additional heat sources.  If kits do feel cold, an old sock filled with rice and microwaved until warm (but not hot!) will do an excellent job of warming them and stay warm for a surprisingly long time.  For very cold kits, holding them against your skin (such as in your shirt) is best for warming them quickly or they can very carefully be held in a warm water bath and thoroughly dried once warm.

 

Cleanliness - without a mother grooming them, kits can get soiled and greasy easily, especially if/when things get messy while bottle-feeding.  I highly recommend trying to keep the nest of kits with a good-natured doe, even if she is not nursing them.  Some does will groom kits that aren't theirs and these does are real gems to have.  If you do not have this option, try to keep the kits as clean as possible while feeding and quickly soak up any spilled milk with paper towel when it happens.  You can wipe them down with a damp cloth and then dry them well.  I rarely find that I need to stimulate kits to urinate and they usually urinate quite readily on their own.  If they do not urinate on their own, you can gently rub their bottoms with a damp, soft cloth or cotton ball and they should urinate soon after.   

 

Nutrition/Gut Health -  start introducing solid foods very early.  I recommend using hay as nest material so that they can begin sampling it at a very young age (by 10 days).  You can also put a few feed pellets in their nest box and you may be surprised how early they sample solids.  Rabbit kits also normally consume their mother's cecotropes (night droppings) to help their gut flora get accustomed to the solid diet that their mother eats.  This is another great reason to keep the kits with a good-natured doe so they can consume some of her cecotropes.  If this is not possible, try to find some cecotropes from another rabbit, although this is very difficult.  

 

CONCLUSION

This is a very broad topic and impossible to fully cover in one blog post, but I hope the information is helpful.  While artificially rearing kits can be very difficult with high risk of mortality, these risks can be greatly reduced by following this guide.  The many tricks to avoid or delay artificial rearing discussed in this article are also beneficial to kit health and survival.  Please feel free to leave a comment or contact me with any questions!

"That was a good meal!"

Happy New Year!

-Barbara 

www.blossomacresrabbitry.webs.com

www.facebook.com/blossomacresrabbitry

Are My Kits Getting Enough Milk?

One of the most common questions I receive from newer rabbit breeders is concern over if their kits are getting enough milk.  This may be due to never seeing the mother nurse her young, as does only nurse their litter once or twice a day, and they are good at doing it when you are not around.  They also rarely ever "check" their nests, which leads many to be concerned that a doe abandoned her litter.  With that in mind however, it is still not uncommon for one or more kits in a litter to not be getting enough milk.  In this article I will describe how to evaluate if kits are getting enough milk and some of the causes as well as solutions to this problem.  I also want to emphasize the importance of being proactive and checking the kits regularly as you can significantly reduce mortality rate by stepping in early when needed.   

There are two initial questions to ask yourself in these situations.
1. Are the kits actually getting the amount of milk they need?
2. If not, is it due to inadequate milk production or inadequate maternal care?

Are the kits actually getting the amount of milk they need?

Well-fed Kits

In well-fed kits, the bellies may range from noticeably round to very large “toad” bellies, white milk can be seen through the skin, kits spend a lot of time sleeping and may also squeak and stir in the box when they sense movement, and mom is lactating well.  

 

Occasionally breeders have the opposite concern that the kits are actually getting "too much" milk.  This is not a cause for concern unless there are other factors at play such as a genetic predisposition for splayed legs in combination with slick floor surfaces, both of which should be avoided.  In my rabbitry, I am always happy to see very big bellies of milk as the kits always thrive.  

These kits are thriving with round bellies full of milk.

______________________________

Under-fed Kits

In under-fed kits, the belly is not round, very little or no white milk will be seen through the skin, the skin may be wrinkled, the kit may be stirring and squeaking quite a bit in the box or may be weak and lack energy, and the kit must be fed soon.  This can also quickly lead to hypothermia.  In older kits, the roundness/fullness of the belly can still be evaluated.

 

This kit has very little milk in its belly and wrinkled skin.

_______________________________

The following tips are with the assumption that the kits are healthy and the only issue is with access to milk.  There are certainly situations where a kit is unhealthy or it may have a genetic issue that prevents it from nursing properly such pituitary dwarfism (peanut).   

Is the mom producing enough milk? 

In my experience, more often than not, the cause of hungry kits is actually an issue with the mom not producing enough milk rather than not taking care of her litter.  

Lactation requires a lot of energy from the mother and she therefore has increased nutritional demands.  Take a moment to look at the NRC nutritional requirements for various stages of rabbit production and check your feed labels to see if you are meeting them.  Lactating does should be fed ad libitum with an increased protein diet of around 17-18% and increased digestible energy.  A rabbit's energy output into milk is very high compared with many other species due to the rate of milk production and richness of the milk that they produce. I have had very good success with supplementing my does' diets during lactation with raw rolled oats which can be purchased from a feed store or grocery store.  I would also recommend feeding a "grow" formula of pellet or something that is formulated for increased nutritional demands such as in lactation.  Be careful with hay quality and quantity during lactation as the nutritional requirements may not be met without carefully supplementing and making sure the doe is consuming enough of the supplement to meet requirements.  If a doe is fed, for example, a diet of Timothy hay and a maintenance pellet during lactation, she will not milk well.  A free PDF of the 1977 NRC Nutrient Requirements of Rabbits can be found here: https://www.nap.edu/catalog/35/nutrient-requirements-of-rabbits-second-revised-edition-1977.

Litter size also plays a role in milk availability as a doe may be producing enough milk for 5 kits, but not for 10.  Feed a doe nursing a large litter really well, but if she still cannot produce enough for all the kits, some or all of them will likely fall behind.  Another interesting consideration (especially with large litters) is the number of teats that a rabbit has (8-10 is average, but they can have 6-12 with independent mammary glands).  Since a rabbit feeds their kits in a very short window of time, there may simply be not enough teats to go around for a large litter.  In these cases, fostering (or grafting) some kits onto another doe that has enough milk is the best option.  I will discuss fostering techniques in the next blog post. 

Heat stress also affects milk production, resulting in lower feed intake and milk yield, so care should be taken to help nursing does stay cool in hot conditions.       

How do you tell if a doe is producing enough milk besides looking at the kits?  Does that are lactating very well will have a pretty pronounced mammary system that you can feel when putting your hand on the doe's belly.  If the area around each teat is raised, that is a good indication of good milk production.

  

This doe is on day 2 of lactation and is lactating extremely well.  You can see and feel the raised mammary glands over her belly.  Many does will not look this pronounced, but will still be lactating sufficiently to raise their litter.  

 

 

You can also express a little bit of milk from the teats to check milk production, especially in animals with less pronounced mammary glands.  You do not want to introduce bacteria when doing this, so clean the area before and after with some diluted iodine and wear gloves.  

 

Occasionally a doe's mammaries can become engorged with a lot of milk that causes her pain.  This often includes the mammary tissue feeling hard and the doe reacting sensitively to touch.  In these situations, the kits can go hungry if not attended to.  Holding the doe while her kits nurse to relieve the engorgement and a warm compress can help alleviate this problem.

 

Although fairly uncommon in rabbits, ruling out mastitis (infection of the mammary glands) is also important.  Symptoms include the mammary area being hot to the touch, fever, and bloody, clumpy, or discolored milk.  If you find signs of mastitis, this will certainly explain kits not getting enough milk and you should consult with your veterinarian for treatment and find another doe to raise the kits or a way to supplement them ASAP.  

Is the mom taking adequate care of the litter?

If no issues are found after evaluating milk production in the mother, it is likely that the doe is not taking adequate care of her kits.  In my experience, this is often in first time moms that are not outrightly rejecting their litter, but are simply not nursing them enough.  I have had good success helping to feed the kits on their mother (which I will cover in more detail in the next post) and the doe's instinct usually kicks in and she takes good care of the kits on her own soon after.

While it is certainly possible to have a doe outrightly reject her litter, I have not run into it personally in 10 years of raising rabbits, likely due in part to the fact that I select for animals that have strong maternal behavior and ensure that they have a stress-free environment to raise their young.  While you may hear about does rejecting litters like it is a common problem, in my experience, so many litter rejections that are talked about are often misidentified with some of the other factors above being the actual source of the problem.  Just because the mom's nest of kits is hungry, doesn't mean she has rejected them.  When a doe is truly rejecting her litter, she will often act aggressively towards the kits.  In these situations, remove the litter ASAP and try to find an alternate way to raise them.

 

Orphans, assisted nursing, fostering, and bottle-raising kits

This will be coming soon in the next post!  

I hope you find this information helpful and please feel free to leave a comment below or send a message with any questions or comments!

Why You Should Reconsider Hay's Place in a Rabbit Diet

With so many feed options out there for rabbits, it can be hard to sort through them and find what is truly best for the health of our animals.  Many sources will recommend a diet of mostly hay (such as the House Rabbit Society recommending it be 80% of their diet and others even recommending 90%) without citing any scientific basis for the nutritive value of their claims.  This type of information gets repeated widely in the rabbit community, ending up in countless articles with continued lack of evaluation of actual nutritional benefit.  "A rabbit's diet should be mostly Timothy hay" is so widely said that it is considered common knowledge to many, but my hope with this article is to prove why it is flawed.   

To preface this article, I want to acknowledge that nutrition in general is such a broad topic with many different strong opinions out there on what is best and what is bad.  Imagine asking 10 random people what the ideal diet for humans is - you will get 10 different answers and many will contradict each other!  It is the same in the rabbit world and I want to emphasize that this entire article is centered around making sure we are providing a diet that meets nutritional requirements, not what specific foods should be fed to meet them with.  This article is not saying that hay is bad, but simply asking the reader to possibly think about hay differently in how it nourishes their rabbits. 

Nutritional Requirements for Age and Productive Status

There is no one-size-fits-all diet for rabbits with nutritional requirements varying by stage of life and production (see table below).  There are certainly other factors impacting nutritional requirements with one example being Angora breeds commonly fed a higher protein feed to support fiber growth (Lebas et al. 2010), so other considerations such as that will impact how to balance the rabbit's diet beyond general recommendations.

Below is a simple table including some of the main nutritional considerations (see sources for more expansive list) for four main stages of life and production.  Included are the recommendations by the National Research Council (NRC) for rabbits in addition to work done by F. Lebas who reported slightly higher nutritional requirements in many situations. 

		Growth	Maintenance	Gestation	Lactation
Digestible Energy (kcal/kg)	NRC (1977)	2500	2100	2500	2500
	F. Lebas (1980)	2500	2200	2500	2700
Crude Fiber (%)	NRC (1977)	10-12	14	10-12	10-12
	F. Lebas (1980)	14	15-16	14	12
Crude Fat (%)	NRC (1977)	2	2	2	2
	F. Lebas (1980)	3	3	3	5
Crude Protein (%)	NRC (1977)	16	12	15	17
	F. Lebas (1980)	15	13	18	18
Calcium (%)	NRC (1977)	0.4	--	0.45	0.75
	F. Lebas (1980)	0.5	0.6	0.8	1.1
Phosphorus (%)	NRC (1977)	.22	--	0.37	0.5
	F. Lebas (1980)	.3	0.4	0.5	0.8

You can see that "maintenance" rabbits have the lowest nutritional requirements.  Maintenance rabbits are rabbits that are fully grown and are not pregnant or raising litters, so pet rabbits would fall under this category as well as adult bucks and does with longer gaps between litters.  Growing kits and pregnant does have similar requirements of more digestible energy and higher protein especially.  Does that are nursing kits have notably higher requirements as well and it is very important to make sure they are meeting these requirements for adequate milk production and to allow the doe to maintain her body condition. 

What happens when these requirement are not met?

While this is by no means an exhaustive list, some symptoms of nutrient deficiency or excess are listed below. 

Nutrient	Deficiency	Excess
Digestible Energy	Weight loss, poor growth, reduced milk production, ketosis, ketoacidosis, fatty liver	Enteritis, obesity, reduced reproduction
Fiber	GI stasis, wool block, enteritis	Reduction in digestible proteins creating an energy deficit
Fat	Dull coat, reduced energy intake, reduced milk yield, reduced vitamin absorption	Reduced growth and reproduction, enteritis, heart disease
Protein	Muscle loss, stunted growth, fatty liver, reproductive disorders	Excess excreted through urine, kidney damage
Calcium	Hypocalcemia, osteoporosis, rickets, impaired zinc and phosphorus absorption	Excess is excreted through the urine which may cause bladder or kidney stones
Phosphorus	Rickets, osteomalacia, infertility, abnormal behavior
Magnesium	Wool block, poor growth, alopecia, convulsions	Excess is excreted through the urine
Copper	Anemia, reduced growth, bone abnormalities, greying of black hair, wool block, enteritis	Copper poisoning
Vitamin A	Infertility, abortion, weak newborn kits, ocular lesions, hydrocephalus	Infertility, abortion, weak newborn kits, hydrocephalus
Vitamin K	Muscle weakness, paralysis, respiratory distress, abortion, placental hemorrhage	Nephritis
Vitamin D	Dental problems, weakened immune systems, cardiovascular problems	Impaired movement, anorexia, infertility
Vitamin E	Reproductive failure, myopathy

Nutritional Content of Hay

Let's look at how hay compares to the nutritional requirements of rabbits above.  Timothy hay, which is very commonly specifically recommended for rabbits, averages only 8% protein which is below requirements for all stages of life and production including a maintenance rabbit.  It also averages 1800kcal/kg of digestible energy which is also below requirements for maintenance.  Alfalfa hay, on the other hand, tends to be 12.9-18% protein depending on maturity which can perfectly meet protein requirements depending on quality of the hay, although the calcium content of alfalfa can be too high at 1.2% on average, causing it to be avoided or limited by many.

Quality of hay makes a huge difference in how nutritious it is.  If you feed packaged hay from the store or buy tested hay, you can check the feed label for nutritional content.  If you feed untested hay, you can try to estimate what it may contain based on the grass/legume content, the quality of the hay, and compare to averages for hay of that type and quality.  When the plant matures past its peak quality, the cell walls become more lignified and increasingly less digestible, especially including a pretty significant drop in protein content after plants move from a vegetative state to seed head production.  You want to look for young, tender leaves, stems that aren't super thick, and less maturity of seed heads in the hay.  You will also want to look for a lot of leaves compared to stems as those are the most nutritious component.  First cutting hay is generally lower quality because the plants grow super quickly in the spring and the weather conditions are often too cool/moist to harvest on time in late spring or early summer, delaying harvest to when the crop is losing nutritive value.  That isn't to say that you can't have a high quality first cutting or a low quality second cutting though, so talk to the farmer, pay attention to how mature the hay looks, and try to get tested hay if possible.  Also, if you have had a particularly wet year, chances are the hay will be lower quality, as farmers have to wait for dry windows of time to harvest with plants growing very quickly in the mean time.

Feeding of Pellets with Hay

Pellets are often what is compared to hay or fed in addition to hay, so important to discuss in this context.  A good quality pellet is composed of mostly "hay" itself (alfalfa, grass, or both) and also is balanced to meet a rabbit's daily requirements including vitamins and minerals.  These pellets are known as "complete" pellets and as the name implies, they are designed to be fed as the complete diet.  It is important to follow the feeding directions on the bag for these pellets, as nutritionists have done the hard work of making sure they contain everything needed for your rabbit to have a balanced diet as long as the pellets are fed as directed.  Most complete pellets will list how much pellet to feed daily according to your rabbit's body weight.  Some hay can be fed on top of that, but if you feed less pellet than the daily recommended serving and replace it with hay, the rabbit is likely not meeting requirements. 

Balancing Diets

Many people feed their rabbits some proportion of both hay and pellets, while some feed veggies and greens, specifically exclude pellets, or feed only pellets, but how do you make sure that your rabbit's diet is meeting its nutritional requirements?  With any feed, the quality of the feed matters.  There are good quality pellets and cheap ones full of fillers, good quality hay and overly mature hay that is so low in nutrition it is like feeding straw, and veggies and greens that offer good nutrients while others offer little at all.  It is important as rabbit raisers that we evaluate the nutritional content of what we are feeding our rabbits and the individual quality of the feed.  If you feed a complete pellet, but only provide a portion of the recommended serving and fill up the rest with Timothy hay, the rabbit will not be getting enough protein and will likely also not be meeting other requirements such as digestible energy and vitamins.  Continuing to use an average 8% protein Timothy hay as the example, the more hay you feed, the richer the rest of the diet needs to be to make up for it.  Half a daily serving of a complete diet and the rest Timothy hay will not provide enough protein, but supplementing with a "concentrate" like grain could help make up for the difference.  Nutrients like vitamins are a lot harder to balance this way and shouldn't be overlooked.   

If wild rabbits eat grass, how can feeding natural grass diet not be providing enough nutrition?

Wild animals instinctually seek out the nutrients that they need.  Besides eating grass and other greens, they also seek out bark, twigs, buds, fruits, seeds, and more.  Every year I see young cottontails licking the gravel in our driveway.  Could they be seeking out salt left behind from the previous winter roads or maybe minerals, I don't know, but the rabbits know that they need something that is there.  This kind of foraging based on the rabbit's own instinct is simply not possible with feeding of domestic rabbits.  Domestic rabbits only have access to the the feed that you provide them in the quantity that you provide as a daily ration.  Where a wild rabbit will select only the tastiest and most nutritious bits of feed and leave the rest, the domestic rabbit only has the quantity provided to eat.  This is why it is so important to make sure that the feed you are providing your rabbit with, whatever feed that may be, is meeting their nutritional demands.

Why feed hay?

During digestion, larger (indigestible) fiber particles are moved through the colon where they are later excreted as hard fecal pellets while smaller (digestible) fiber particles (<0.3mm) are moved through the cecum where they are fermented and excreted as cecotrophs (night droppings) which the rabbit then consumes again.  These larger particles mechanically stimulate motility of the cecum and colon.  Very fine particle size feeds lead to increased retention time in the gut, lowering GI motility.  The question then becomes: how fine is too fine?  Obviously particle size of long stem hay is greater than that of a pelleted feed, but is the particle size of a coarsely ground pellet large enough?  There have been several research studies (some referenced below) on the effect of pellet particle size with somewhat inconclusive results on GI health, but fairly consistent results of increased growth and nutrient utilization by rabbits fed a finer particle feed.  While I don't have an answer to if average pellets contain large enough particle size for optimal GI health, I do know that quite a few rabbit raisers feed pellets exclusively  with no issues.  For someone feeding exclusively pellets, I would personally suggest that they try to find a coarsely-ground pellet or feed just a little bit of long stem hay in addition to the full daily ration of complete pellet.  Pellets manufactured by an extrusion process may also tend to retain longer particle length.   

A common misconception is that hay is required to wear down a rabbit's teeth.  Rabbits have constantly growing teeth, but proper dentition or "bite" is largely genetic and will prevent teeth from overgrowing.  If a rabbit has a bad "bite" the teeth will not get worn down properly even on a diet heavy in hay.  Many rabbit raisers who feed no hay (exclusively pellets) never encounter malocclusion because they breed for proper dentition in their animals.  Müller et al. (2014) studied diet form effect on dental growth and wear and concluded that diet alone is not likely to cause dental problems due to flexible growth that reacts to wear and found no difference between animals fed hay or pellets.   

Hay has value as behavioral enrichment for rabbits, helping to relieve boredom and encourage natural behavior.  While there are many things that can be provided as behavioral enrichment, rabbits do love to chew on and make a mess of hay.  This is an additional benefit of feeding hay outside of nutrition.

Conclusion

While there are many different types of food that can be fed to rabbits, the most important consideration is that the total ration meets the nutritional demands of the rabbit.  Timothy hay which is most commonly recommended for rabbits, in addition to other grass hays, do not contain enough nutrients on their own to meet nutritional demands.  Common recommendations of large quantities of hay in the diet without proper instruction on balancing the remaining nutrients can be very harmful to the health of these animals.  It is very important to balance the nutrients in the entire ration and not just one component of it. 

As always, please feel free to contact me or leave a comment below with any questions or comments! 

-Barbara

References

NRC Requirements for Rabbits: https://www.nap.edu/catalog/35/nutrient-requirements-of-rabbits-second-revised-edition-1977.

Nutritional pathology in rabbits: http://www.caza-narg.ca/ref/ref200806-7.pdf

Digestive disorders: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7149370/

Evaluation of nutritional content of hay: https://extension.usu.edu/rangelands/ou-files/Deter_forage_value_hay.pdf

General Nutrition of Rabbits: https://www.merckvetmanual.com/exotic-and-laboratory-animals/rabbits/nutrition-of-rabbits#v5625687

Nutrient requirements: https://pdfs.semanticscholar.org/0985/0f88ae2a5af2ccd02d41456991b6128dfac0.pdf

Particle size of feed: Vincenzo Tufarelli , Salvatore Desantis , Sara Zizza & Vito Laudadio(2010) Performance, gut morphology and carcass characteristics of fattening rabbits asaffected by particle size of pelleted diets, Archives of Animal Nutrition, 64:5, 373-382, DOI:10.1080/1745039X.2010.496945

Sogunle et al. 2014 - Feed forms of different particle sizes: growth response, carcass yield and intestinal villus morphology of growing rabbits -
Bulletin UASVM Agriculture 71(1) / 2014Print ISSN 1843-5246; Electronic ISSN 1843-5386

Effect of diet on wear of teeth:

Müller et al. (2014) Growth and wear of incisor and cheek teeth in domestic rabbits (Oryctolagus cuniculus ) fed diets of different abrasiveness https://doi.org/10.1002/jez.1864