Fig. 6. Comparisons of excreted N (a) and percent urine N (b) from the present study with calculated values for dairy heifers from referenced studies (1) Wilkerson et al. (1997), (2) Rotz (2004), (3) Nennich et al. (2005), (4) Kebreab et al. (2002), (5) Marini and Van Amburgh (2003), and (6) James et al. (1999).