Why is small intestine in herbivores longer than in carnivores?

The small intestine in herbivores is longer than in carnivores because plant-based diets are generally more complex and require more extensive processing for efficient nutrient extraction. Herbivores need a longer digestive tract to provide sufficient time for the breakdown of cellulose and other plant fibers, as well as for the absorption of nutrients from plant material. This lengthier digestive system allows herbivores to extract maximum nutrition from their plant-based diets to meet their metabolic needs.