Degradabilidade in situ da matéria seca, proteína bruta e fibra em detergente neutro, de diferentes gramíneas, em novilhos suplementados com misturas múltiplas

Abstract

The experiment was conducted with the purpose of evaluating the effect of different mineral supplements on the degradability of dry matter, crude protein and neutral detergent fiber in cattle on pasture, at Escola Agrotecnica Federal de Cuiabá – MT, from July to November, 2001. It was utilized 12 steers. Twelve steers aged 18 months and average weight of 240 kilograms, from several breedings and rumen fistulated, were utilized. From the differing management of the pasture, the area was divided into six padlocks, provided with covered drinker and feeder. The rotated grazing with 14 days occupation and the stocking rate of 1 animal/ha was utilized. The treatments were: T0 - pasture without minerals (control); T1 - pasture with mineralized salt; T2 - Pasture with mineralized salt plus urea; T3 - Pasture with mineralized salt plus urea plus corn; T4 - pasture with mineralized salt plus urea plus soybean meal; T5 – pasture with mineralized salt plus urea plus soybean meal plus corn. The sample of forage was obtained by the technique of simulated grazing and homogenized. The forage used in the degradability trial showed a mean of 8.4% of CP and 77.2% of NDF on the DM basis and was incubated in natura with 37.2% DM. The in situ ruminal degradability was obteined with the nylon bag technique. Each nylon bag contained 20 mg DM/cm2 of surface and incubated in rumen for 0, 3, 6, 12, 24, 36, 48, 72 and 96 hours. The potential and effective degradability and the undegradable fraction of DM, CP and NDF were analyzed utilizing the Randomized Block Design with six treatments and six replicates and means compared by the Scott Knott test. The blocks were arranged by considering each fistulated animal. The results obtained showed that, for the effective degradability of DM, there was difference (P<0.07) among the treatments and the degradability rates of CP and NDF of the forage were not influenced (P>0.05) by the treatments. Feeding nitrogen and/or energy source in supplement provided efficient and effective degradability of DM, on average, 6.8% bigger than the others without these sources.