Suplementacao de bovinos con misturas multiplas em pastagem de Brachiaria brizantha cv. Marandu no periodo da seca.

Spanish; Castilian. En una finca de la region del Cerrado, la Empresa Brasileira de Pesquisa Agropecuaria (Embrapa-Cerrado) evaluo las ventajas del uso de una mezcla multiple, en la cual se sustituyen la proteina natural por urea y diferentes fuentes de energia en pasturas de B. brizantha cv. Marandu, establecidas en un Latossolo Vermelho Escuro de textura arcillosa. El experimento se realizo durante 84 dias en la epoca seca de 1997. Se utilizaron 160 novillos Nelore, con un peso vivo, promedio, de 175 kg en un sistema de pastoreo continuo en cuatro, potreros. Se utilizo un diseno experimental completamente al azar con cuatro tratamientos (suplementos): (1) sal mineralizada con 38% de superfosfato triple (testigo); (2) mezcla Embrapa Cerrado: maiz triturado 30%, afrecho de soja 15%, urea 10%, sal mineralizada 35%, sal comun 10%; (3) maiz triturado 36.4%, afrecho de soja 7.5%, urea 11. 1 %, sal mineralizada 35%, sal comun 10%; (4) maiz triturado 42.7%, urea 12.3%, sal mineralizada 35%, sal comun 10%. La disponibilidad de forraje durante el periodo del ensayo permanecio por encima de 4.5 t/ha de MS. La presion de pastoreo vario entre 7% y 8%, aunque la carga animal promedio fue de 0.9 UA/ha. El contenido de proteina cruda fue inferior a 6% en agosto, pero posteriormente aumento. La menor DIVMS (55%) ocurrio en agosto y la fibra en detergente neutro (FDN) vario de 60% en junio a 72% en agosto. Los animales suplementados con la mezcla multiple desarrollada por Embrapa Cerrados presentaron ganancias de peso vivo similares a los que consumieron las otras mezclas en oferta; no obstante, fueron superiores a las ganancias de los animales que solo recibieron sal mineralizada. La suplementacion con la mezcla Embrapa Cerrado represento un aumento del 46% en la ganancia liquida por animal, con un retorno de US$3.59 por cada dolar invertido.

English. This field experiment was carried out by Embrapa Cerrados on a private farm, on a Brachiaria brizantha cv. Marandu pasture over a dark-red Latosol. The objective was to test different strategies for cattle supplementation, based on urea as substitute for natural protein, as well as milled corn and soybean meal as energy sources. During the dry season (84 days), from June to September of 1987, 160 Zebu cattle, averaging 175 kg live weight were assigned to four treatments, in a completely randomized design. The treatments (supplements) were: (1) mineral salt with 38% of triple superphosphate content; (2) milled corn 30%, soy bean meal 15%, urea 10%, mineral salt 35%, common salt 10%; (3) milled corn 36.4%, soy bean meal 7.5%, urea 11. 1 %, mineral salt 35%, common salt 10%; (4) milled corn 42.7%, urea 12.3%, mineral salt 35%, common salt 10%. The mean monthly forage available presented 4,500 kg of dry matter per hectare along the season. The grazing pressure during experiment was 7%, and stocking rate 0.9 AU/ha. The crude protein content was high in June and July but fell to less than 6% in August. The in vitro dry matter digestibility decreased along the season, while the neutral detergent fiber percent increased in August. The animals fed with supplements 2, 3 and 4 presented similar live weight gain, which was superior to those in treatment 1. Supplement 2 increased in 46% the net income of the enterprise, providing US$3.59 of economic return for each US$ invested.