How Do Dairy Cows Perform When Fed Grass vs. Legume Diets?

INTRODUCTION Alfalfa is the primary forage fed to lactating dairy cows; however, there is renewed interest in utilizing grass forages in lactating dairy cow diets particularly because of farm nutrient management issues. Yield and perceived quality is generally lower for grass species compared to legumes while other agronomic factors such as longer stand life, requirement for nitrogen fertilizer, and more tolerance of manure spreading, which allows for greater and more frequent manure application than on alfalfa, may make grasses more desirable. Grasses may also compliment diets with high levels of co-products from the ethanol and food industries better than legumes because grasses are generally moderate to low in crude protein (CP) compared to alfalfa and most co-products contain a significant amount of CP. The purpose of this paper is to review some results and limitations of previous lactation studies that have compared the feeding value of grass and legume forages, and provide information on nutritional and cell wall differences between grasses and legumes in order to better understand the utilization of these forages by dairy cows.