I would try not to use pineapple if its just a gut slowdown. It can be used if a rabbit has stopped eating completely, though.
Here's a pending Library entry that explains the reason for sugary stuff like pineapple. It should only be given under certain circumstances.
FORCE FEEDING
Great care should be taken when force feeding ill rabbits for several reasons.
If a blockage is located in the stomach or at the pylorus, a narrow passage between stomach and the intestine, adding food only increases the pressure in the stomach and may increase the risk of rupture at the pylorus. (Gut motility drugs should also never be given to rabbits with a possible blockage for the same reason).
Sick rabbits also often have low body temperatures which makes muscles stiff and it difficult for the rabbit to swallow properly increasing the possibility of choking. This also causes organs related to digestion do not respond properly, affecting digestion of the food.
If a rabbit has not eaten in 24 to 48 hours and feels cold, try to warm it up with a hot water bottle, a rice sock, then slowly try nourishment.
Rabbits Online recommends a small amount of Nutri-Cal, a high calorie, vitamin-rich paste in a tube available from pet stores and vets. Alternatively, you can slowly give it some luke-warm water with a bit of diluted honey or sugar. The calories will provide energy to the rabbit and allow its organs to start working properly, avoiding fatal hepatic lipidosis, or 'fatty liver disease', which can occur as little as 48 hours after the rabbit stops eating. More at risk for this disease are obese (overweight) rabbits or rabbits with high energy demands like pregnant does or nursing mothers.
Sugar should be avoided with rabbits suffering from a bacterial imbalance in the GI tract. ('Poopy butt' or what appears to be diarrhea is symptom). If this is the case, a rabbit should be receiving rehydration in the form of Pedialyte (a children's electrolyte replacement drink) or another non-sugar source, and a product like Critical Care (a high fiber powder made into âmush). Canned pumpkin is another good source low sugar carbohydrates and high fiber.
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