Desempenho ponderal de novilhas mestiças Holandês x Zebu submetidas a duas estratégias de suplementação mineral

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The ponderal performance of heifers under rotational grazing fed two types mineral supplement was evaluated. A total of 25 heifers Holstein x Zebu, including nine regulator animals and 16 test animals, was divided into four treatments: mombaçagrass (Panicum maximum, CV. Mombaça) with selective salt (MSS), mombaçagrass with commercial salt (MSC), elephantgrass (Pennisetum purpureum, CV. Napier) with selective salt (ESS) and elephantgrass with commercial salt (ESC). Average daily live weight gain (DWG) was calculated by weighing the test animal every 28 days after fasting of 16 hours. Dry matter intake (CMSLFV) and apparent digestibility (DMSLFV) of green leaf blade were evaluated with chromium oxide and indigestible neutral detergent fiber, as external and internal markers, respectively. Mineral supplement intake was measured and the levels of dry matter, crude protein, and of Ca. P, K, Mg, Na, Cu, Zn, Fe and Mn only in grass leaves samples. A completely randomized design in 2 x 2 factorial arrangement (grass and mineral mix), was used. Each treatment was composed by four animals, and each animal as considered a experimental unit. Only Cu, Na and Zn were deficient in the forages. The CMSLFV were not affected by the studied variables and no significant interactions were observed. There was interaction between salt mix and grass for DMSLF. The DWG was affected only by grasses, the performance that ingested elephantgrass was higher. The nutritional composition of the elephantgrass was slightly better than that of mombaçagrass what probably provided better weight gains for the animals in this treatment. © 2008 Sociedade Brasileira de Zootecnia.