No, guinea pigs should not eat avocado. Avocado contains a substance called persin, which is toxic to many animals, including guinea pigs. Eating avocado can cause digestive upset, breathing difficulties, and even death in guinea pigs. It's important to stick to foods that are safe for guinea pigs to eat, such as hay, fresh vegetables, and fruit in moderation. If you suspect that your guinea pig has eaten avocado or any other toxic substance, contact your veterinarian immediately.