The researchers studied how feeding a mix of green NB21 and Leucaena forage to calves affected their growth and nutrient utilization compared to a diet of dry grass and concentrate. They found that calves in the Leucaena-fed group gained less weight but had higher digestibility of nutrients like protein and energy. However, after two months, all calves fed Leucaena showed ulcers in their mouths with bleeding. This suggests that adding hybrid Napier grass to the diet did not prevent the negative effects of Leucaena on the calves.