Basal feeds have a high proportion of easily digestible
Answer Details
The sentence is saying that basal feeds have a high proportion of easily digestible nutrients. It goes on to specify that the type of nutrient that is easily digestible is not mentioned, but it suggests that basal feeds may contain a high proportion of either carbohydrates, proteins, or fats that can be easily broken down by the animal's digestive system. Out of the options given, the most likely answer is "carbohydrates" since these are the primary source of energy in most animal diets and are often found in high quantities in basal feeds.