Winter Supplementation of Beef Cows in the Intermountain West David Secrist, USU Extension Beef Cattle Specialist
Introduction Feed costs are the most significant expense of most ranching operations in the Intermountain West. Year-round grazing opportunities, hay cost and availability, calving season, cow size, milk production, and feeding logistics are all considerations in a supplementation program. The key to effective winter feeding is to balance the cost/benefit ratio of the supplementation programs while meeting nutritional demands at a minimal cost. The cost includes both the actual feed cost and the cost of implementation, which encompasses equipment, facilities, and labor. Individual ranch operations vary widely in management goals, resources, and supplementation needs. Some ranches have access to grazing year-round, while others feed supplemental forage for a significant portion of the year. While the form of supplementation may differ, cow requirements are primarily determined by the stage of production and the environment to which they are exposed. Whether harvested or grazed, forage quality, relative to cow requirements, will determine supplemental needs.
Basic Rumen Function The cow's digestive system functions as a fermentation vat. Microbes in the rumen break down plant components, producing volatile fatty acids (VFAs), microbial protein, heat, and gas. VFAs are produced in the rumen by microbes, resulting from the breakdown of fibrous plant material, sugars, and starch. VFAs are absorbed into the bloodstream and are the primary source of energy for the cow. Microbial protein is derived from the proliferation of microbes in the rumen, which are 1
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Volatile fatty acids are absorbed into the bloodstream and are the primary source of energy for the cow. Protein-deficient diets will result in lower forage digestibility and forage intake. Cattle on low-quality forage need most of the protein in the diet as natural or plant-derived protein. Every other day or 3 times per week, protein supplementation is adequate for mature cows. Feed intake on a forage diet is primarily driven by cow body weight and forage quality.