FIGURE 4.

Model of intake and digestive function in nonreproductive females compared with large males and lactating females. Width of arrows reflects amount of food intake, length of arrows indicates rate of digesta passage, and shading indicates density of nutrients in food. Diagrams of digestive tract are stippled to reflect potential changes in fibrosity of food for males and increases in postruminal size and function of lactating females (modified from Barboza & Bowyer, 2000). This figure is modified from the original to include new information (Zimmerman et al., 2006) documenting that the rumen of lactating females is larger and has greater papillae length and width compared with that of nonlactating females (modified from Stewart, Bowyer, & Weisberg, 2011)