The relationship between grazing a high quality shrub legume, blood serum urea (BSU) and daily weight gain (DWG) in F1 Holstein x Zebu heifers was evaluated. Two pastures were compared: 1) high crude protein diet (HCP): Cratylia argentea + Brachiaria brizantha Toledo grass, and 2) low crude protein diet (LCP): Brachiaria brizantha Toledo grass alone. Grazing of each treatment lasted 164 days. Dry matter yield (DMY), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF)

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... d lignin (LIG) were evaluated in both pastures. Before grazing, DMY at HCP and LCP was 1922 ± 405 and 770 ± 405 kg ha-1, respectively, and CP was 8.3 ± 0.85 and 8.7 ± 0.85 %, respectively. The NDF, ADF and LIG of Toledo grass at HCP and LCP were similar, averaging 73.1 ± 0.92, 42.7 ± 1.2 and 13.5 ± 0.7 %, respectively, while in C. argentea averages at HCP and LCP were 51.6 ± 0.58 % (NDF), 32.5 ± 0.85 % (ADF) and 16.7 ± 1.3 % (LIG). The BSU was 11.01 ± 0.35 (HCP) and 7.87 ± 0.35 (LCP) mg dL-1. Average DWG in HCP and LCP was 839 ± 258 and 580 ± 278 g day-1, respectively. In conclusion, in F1 Holstein x Zebu heifers DWG can reach over 800 g day-1 when grazing a high CP diet.