Optimizing Starch Concentrations in Dairy Rations

Currently, many nutritionists consider only the total nonfiber carbohydrate (NFC) fraction when formulating rations for lactating dairy cows. Increasingly, we need to measure the components that comprise NFC (starch, sugars, soluble fiber, and β-glucans) and formulate rations that optimize the concentration of each component in the diet. Starch is the major NFC fraction in dairy cattle diets, and some research has attempted to determine optimal dietary concentrations of either NFC or starch. However, an optimal amount of dietary starch will be a function of several factors, including the inherent degradability of the starch source, processing method, amount of soluble protein, neutral detergent fiber (NDF) content, feeding method, and environment. Commonly, dietary starch recommendations range between 23 to 30% of ration dry matter (DM) depending on forage content of the diet. The basis for this range in recommendations is a combination of some research but mostly anecdotal and experience-based observations in the field. The purpose of this paper is to explore some of the key factors that influence the optimal content of dietary starch, particularly considering diets high in fibrous byproducts.