The expansion of the corn-based ethanol industry has resulted in an abundance of byproduct feeds. Research with these feedstuffs is limited in beef cow/calf production systems. A series of studies were conducted to evaluate the supplementation of byproduct feedstuffs for beef cows consuming low-quality forage.Delinted, extruded expelled cottonseed meal provides a rich source of degradable intake protein but is moderate in contribution of energy. Similar cow performance, diet intake and digestibility, milk production and composition, and reproductive performance was achieved by supplementation of delinted, extruded-expelled cottonseed meal as compared to traditionally used cottonseed meal-based supplements when formulated for isonitrogenous intake. Dried distiller's grains with solubles is moderate in degradable intake protein and is a rich source of supplemental energy. To determine the appropriate supplementation level of dried distiller's grains with solubles for beef cows consuming low-quality forage, increasing feeding levels of dried distiller's grains were evaluated and compared to a traditional cottonseed meal/wheat middling based supplement. At equal intake of dry matter and crude protein, similar cow performance, diet intake and digestibility, milk production and reproductive performance was achieved for dried distiller's grains as compared to the traditional supplement. Feeding increasing amounts of dried distller's grains with solubles did not negatively influence forage intake or diet digestibility. Results from the studies in this dissertation indicate that byproduct feedstuffs are viable supplement options in beef cow/calf systems. Nutrient composition of byproduct feedstuffs is highly variable and should be analyzed prior to use. Due to fluctuations in feed costs, economic feasibility of using byproduct feedstuffs should compared to traditional feedstuffs.Department of Animal Scienc
