Malus or crab apples are usually found in the northern hemisphere and are known for their woody flavour and sour taste. It is a fruit that is often used in cooking because it is so sour.
So can rabbits eat crab apples at all, and if they can how much can they eat of them?
To find out more about them, the best place to look is the nutritional data to really get under the skin of them.
In particular, the sugar, calcium, fat, starch, phosphorus, and acidic content is of particular interest, as its those nutrients that have the most detrimental effect on rabbits.
Source wikipedia
Calorie Information
Amounts Per Selected Serving % DV
Calories 76.0(318 kJ) 4%
Total Carbohydrate 20.0g 7%
Total Fat 0.3g 0%
Saturated Fat 0.0g 0%
Monounsaturated Fat 0.0g
Polyunsaturated Fat 0.1g
Protein 0.4g 1%
Vitamin A 40.0IU 1%
Vitamin C 8.0mg 13%
Thiamin 0.0mg 2%
Riboflavin 0.0mg 1%
Niacin 0.1mg 1%
Vitamin B 120.0mcg 0%
Calcium 18.0mg 2%
Iron0.4mg 2%
Magnesium 7.0mg 2%
Phosphorus 15.0mg 1%
Potassium 194mg 6%
Sodium 1.0mg 0%
Copper 0.1mg 3%
Manganese 0.1mg 6%
Cholesterol 0.0mg 0%
Source nutritional data
As you can see, crab apples are low in particularly everything that it is of concern except for acidic content, which is to be expected. So they are not bad at all for rabbits to eat.
However, their sour taste may cause discomfort to rabbits so do feed with caution.
My personal preference is to feed them standard apples in small amounts as they don’t have the sour taste of crab apples, however if you do choose to feed them crab apple, then feed them sparingly in small amounts