Jackfruit is also known as jack tree, jakfruit, or sometimes jack or jak. It is the largest tree-borne fruit and reaches as much as 80 pounds in weight, 36 inches in length and 20 inches in diameter.
So can rabbits eat Jackfruit at all?
Lets take a look at their nutritional data, in particular their acidic, phosphorus, calcium, fat, fibre, and sodium content are of particular interest.
Nutritional value per 100 g (3.5 oz)
Energy 397 kJ (95 kcal)
Carbohydrates
Sugars 19.08 g
Dietary fibre 1.5 g
Fat
0.64 g
Protein
1.72 g
Vitamins
Vitamin A equiv.
beta-carotene
lutein zeaxanthin
(1%)5 μg
(1%)61 μg
157 μg
Thiamine (B1) (9%)0.105 mg
Riboflavin (B2) (5%)0.055 mg
Niacin (B3) (6%)0.92 mg
Pantothenic acid (B5)
(5%)0.235 mg
Vitamin B6 (25%)0.329 mg
Folate (B9) (6%)24 μg
Vitamin C (17%)13.8 mg
Vitamin E (2%)0.34 mg
Trace metals
Calcium (2%)24 mg
Iron (2%)0.23 mg
Magnesium (8%)29 mg
Manganese (2%)0.043 mg
Phosphorus (3%)21 mg
Potassium (10%)448 mg
Sodium (0%)2 mg
Zinc (1%)0.13 mg
Link to USDA Database entry
source wikipedia
As you can see jackfruit contains a hint of phosphorus, quite a lot of acidic content, but an awful lot of sugar content.
This means that rabbits cant eat jackfruit because it is just too sweet for them to eat. If they have a nibble of it, that would be fine but nothing more than that as it will just hurt their tummies unfortunately.