Evaluación de la presión de pastoreo en tanner (Urochloa arrecta) y la Suplementación estratégica en mautes mestizos en bosque seco tropical y suelos neutros Evaluation of grazing pressure in tannergrass (Urochloa arrecta) and strategic supplementation on growth crossbred steers in tropical dry forest and neutral soils

In order to evaluate the effect of grazing pressure in tannergrass (Urochloa arrecta (Hack. ex T. Durand & Schinz) Morrone & Zuloaga) and strategic supplementation in crossbred steers a research was carried out research in counties Sucre, Zulia State, Venezuela, witha tropical dry forest area (1745 mm and 28.6oC) and sandy loamy soils and neutral (pH 6.5-6.6). Two grazing pressures were used (GP): high (HP) and low (LP) (20 and 14.3 kg body weight (BW).kg dry matter (DM)-1.d-1, respectively) and two levels of strategic supplementation (SS): with (WS) and without supplementation (NS) (0.5 and 0 kg DM.100 kg LW-1.d-1, respectively). The supplement was a mixture of palm kernel meal (65%), poultry litter (25%), minerals (5%) and molasses (5%). The experimental design was completely randomized with replicated measures over time (8 cycles of grazing). The outcome variables were: forage mass before and after grazing (HMBG and HMAG, t.ha-1), crude protein (CP, %), neutral detergent fiber (FDN, %), acid detergent fiber (ADF, %), acid detergent lignin (ADL, %), in vitro dry matter digestibility (DMD, %), daily weight gain (DWG, g.d-1) and live weight gain (LGH, kg BW.ha-1.yr-1). The variance analysis showed that GP affected (P<0.01) the HMBG (2.78 HP vs. 2.66 LP) and HMAG (1.20 HP vs. 1.12 LP), and (P<0.05) the ADG (434.8 HP vs. 588.4 HP). Meanwhile, the SS had an influence (P<0.05) on the ADG (574.1 WS vs. 449.1 NS). The effect was found (P<0.01) in GPxSS interaction on HMBG (2.83 HPNS; 2.75 LPWS; 2.73 HPWS and 2.56 LPNS) and HMAG (1.23 HPNS; 1.17 HPWS; 1.15 LPWS and 1.10 LPNS). The best response was obtained by using a LP and WS.