Final answer:
The least digestible fractions of crude fiber are components like cellulose and lignins, which are insoluble fibers and resistant to the body's digestive enzymes. Table 17.4.9 shows different proportions of dietary fiber in foods, delineating between nonfermentable (less digestible) and fermentable fibers (more digestible).
Step-by-step explanation:
When considering the least digestible fractions from a feed sample in regard to crude fiber, we are typically referring to components like cellulose, lignins, and certain hemicelluloses. These elements are considered insoluble fiber, and they are resistant to the body's digestive enzymes, making them less digestible compared to other components of the dietary fiber. In contrast, soluble fibers, such as pectins, beta-glucans, and some oligosaccharides, tend to be more digestible because they can be fermented by the bacteria in the human gut.
Dietary fiber plays a crucial role in maintaining digestive health, but the overall digestibility can vary significantly between different types of fiber and between different foods. As represented in Table 17.4.9, different foods contain varying proportions of total dietary fiber, nonfermentable fiber, which includes the least digestible fractions, and total fermentable fiber, which is more easily processed by gut bacteria.