Many producers turn lactating beef cows out on pasture in early spring, just prior to breeding attempts. At this time, early forage growth tends to be characterized by a relatively high ratio of crude protein (CP) to total energy, and dry matter (DM) is at its lowest level (Kirchhof et al., 2010). As the season progresses and the plant matures, CP as a percent of DM declines, while total percent DM increases (King et al., 2012). Indigestible fiber, in contrast, is fairly low in early spring, increasing throughout the season (King et al., 2012). Acid detergent fiber (ADF) and neutral detergent fiber (NDF) are measures of indigestible fiber. Because spring pasture is so moist, gut fill can become an issue; if the cow is unable to consume more energy than she expends, she experiences a negative energy balance, possibly lowering weight and bod