Feeding plant-based by-products to dairy cattle has become so commonplace for some of the ingredients that they are no longer thought of as secondary products from food processing. These feed ingredients allow for more economical approaches for meeting the nutritional needs of dairy cattle and contribute to improving farm profitability. The by-products vary in total fiber (NDF) and the characteristics of the fiber for stimulating chewing and saliva production and providing energy to the cow. Oftentimes, these fiber sources can be used for partial replacement of forage, but even more commonly, they can be used to supply highly digestible fiber to replace rapidly degraded starch in high grain diets for lactating cows, providing for a slower rate of carbohydrate digestion and maintaining of rumen pH. Utilization of these feeds by ruminants is very important in environmental sustainability of food systems.