Rabbits are strict herbivores. Their incisors and cheek teeth grow constantly. They have been designed to tear and grind very tough grass blades and leafy foods. The teeth are worn down (and so, in nature, remain just right) by the action of eating.
It's fine to give your rabbit fruit branches to chew for amusement. But it is chewing food that wears the teeth correctly. Rabbits need a diet high in vegetable fibre (from grass and leaves) to maintain their teeth in good order and to promote normal stomach, intestinal and large bowel activity. Grass and leaves are hard for animals to digest. Rabbits have evolved to cope by digesting the food largely in the last part of the intestines. Consequently, to really get the goodness out of the food, it has to be eaten twice! Rabbits do two kinds of poo! The soft, squidgy, green, sticky variety of rabbit poo are digested food, ready to be eaten again. This way the rabbit gets all the goodness from the coarse food they are especially made to eat. The true waste poos are the ones the rabbit does not eat and so these are the ones you are most likely to see. These are the dark, dry-looking poos. When all is well, you are not so likely to see the edible poos as they are prized by your rabbit, who will generally eat them as soon as they are passed.
If you are seeing large quantities of soft 'squidgy' green poos, there may be something wrong with your rabbit. The poos may be normal, but your rabbit is not eating them.
The biggest mistake people make with rabbits is to over feed high calorie foods such as commercial pellets and grains, and not to feed enough high-fibre foods such as hay and greens. This leads to obesity and bowel problems. The most important part of a rabbit's diet is an unlimited supply of grass and hay (which is dried grass). Grass and hay supply the essential high-fibre as well as protein, minerals, vitamins and carbohydrates. They are the best preventative treatment for teeth troubles and for stomach and bowel motility problems such as 'furballs' and chronic soft stools. Feeding the right diet makes hairball laxatives and anti-diarrhoea preparations unnecessary.
The quality of hay can vary with the time of year (traditional hay in Britain is made in summer and the quality will be poorer if last year's hay is being fed). Hay should be fed in a box or rack. It should be stored in a cool, dry place in an open bag to prevent mould. Damp hay can become mouldy and should be thrown away. Rabbits can and should be fed hay at any age. Don't feed alfalfa hay. It is too high in calories and calcium and can cause urinary problems.
The other really important part of your rabbit's diet is fresh, leafy greens. Greens do not cause diarrhoea. The exception to this is when rabbits have been maintained on a low-fibre, high -calorie diet such as a commercial grain or pelleted diet, and then are suddenly introduced to greens. On the commercial diet, the intestines are likely to be sluggish. Introduction of greens is likely to 'speed up' the intestines; the change will shock the large boewel bacteria, resulting in a temporary period where the poos are a bit sloppy. This usually stabilises within about a week as the intestines and bacteria adjust. If your rabbit has never really had greens, introduce hay, cut the commercial food right back and after a couple of weeks of a lot of hay and not much 'rabbit food', gradually introduce greens into the diet.
Feed at least three different types of greens daily so that a range of nutrients is provided. Greens should be washed thoroughly. Uneaten fresh foods should be removed after 3-4 hours to prevent spoilage. Feed at least a heaped cup of greens daily to a 2Kg rabbit. This can be increased to double or triple as your rabbit becomes used to it. Some examples of nutritious greens are: dandelion greens (and flowers), raspberry leaves, kale, mustard greens, escarole, endive, raddichio, collard greens, beet greens, carrot tops, parsley, turnip tops, romaine, Swiss chard, bok choy, mint leaves, cabbage (red and green), etc. Use dark, tough, leafy greens as opposed to light-colored thin-leafed greens such as iceberg lettuce.
Other vegetables and fruits can be fed in smaller amounts (up to a combined total of 1 heaped tablespoon per 2kg body weight daily). Examples of these foods are pea pods (not the peas), carrots, apples, pears, peaches, strawberries, raspberries, blueberries, squash, tomatoes, papayas and mangos.
Stay away from starchy and food with a high sugar content such as bananas, peas, corn, beans, grapes, white and sweet potatoes. Cereal grains and cereal products can cause digestive upsets due to their high starch content and high calorie content and in general should not be used.
So, don't feed: bread, biscuits, crackers, rolled oats, breakfast cereals and other grain products. Although many people feed these treat foods because their rabbits love them, they cause obesity and chronic soft stools. Don't introduce these foods in the first place. That way your pet will only know good nutrition and never know about the 'junk food' he or she is missing!
Commercial rabbit pellets were originally designed to promote rapid growth, weight gain, and ease of feeding for production rabbits (meat and fur) and laboratory rabbits. They are very efficient at what they are designed to do, but for the house rabbit that is to live out a full life, the unlimited feeding of a commercial pellet may be a problem. Once rabbits are fully grown, they don't need to put on more weight. Feed your pet a commercial pellet that is designed for the maintenance of the adult rabbit, with a fibre content of 18% or higher, a protein content at around 13-14% and fat content at no more than 3%.
Once a young bunny has reached its adult size (4-8 months depending on the breed), we recommend cutting back the pellets to 1/8 - 1/4 cup per 2Kg body weight per day as a MAXIMUM.
Remember, there is always hay available so your pet will never go hungry. Pellets should be bought in amounts that will be used within 3 months and kept in a closed container in a cool, dry place to prevent spoilage. Do not use pellet mixes that contain grains and seeds along with the pellets. The addition of the grains and seeds only add to the calorie and fat content which can result in obesity, liver and intestinal disease. Some rabbits that are obese and have difficulty losing weight on pellets may have to have them removed from the diet altogether, but this should be done only under your vet's supervision. Crash dieting a fat rabbit is not safe.