Valor nutritivo das silagens da Brachiaria decumbens colhidas em três idades

Abstract

It was aimed to evaluate the nutritional value of the Brachiaria decumbens grass silage harvested at 56, 84 and 112 days of growth. The experimental design was completely randomized and means were compared by Studant-Newman-Keuls at 5% level of significance. At first was evaluated, Chapter 3, the intake and apparent digestibility in sheep,of the nutrients from the Brachiaria decumbens grass silage in three ages of cut. Were not observed difference in dry matter intake (P>0.05) by the sheep. It was found that the diet of Brachiaria decumbens grass silage harvested at 56 days presented (P<0.05) the highest apparent digestibility of dry matter (ADDM) and organic matter (ADOM) whem werecompared to the treatments containing silage harvested at 84 and 112 days of regrowth. It was observed higher (P<0.05) intake and apparent digestibility of the crude protein, and higher (P<0.05) apparent digestibility of neutral detergent fiber (NDF) and acid detergent fiber (ADF) for the treatment containing the silage made at 56 days. In the Chapter 4, wasevaluated the energy partition and the methane production in sheeps fed with Brachiaria decumbens grass silage in three different ages of cut. The intakes of digestible energy (DE), metabolizable energy (ME) and net energy (NE) were lower (P<0.05) for the animals receiving the oldest material. The values of the DE of the Brachiaria decumbens grass silageranged from 1.72 to 2.27 Mcal/kg of dry matter (DM), as that the treatment ensiled at 56 days had the highest (P<0.05) value and the material made at 112 days resulted in lower (P>0.05) value. Similar result was founded between the treatments when was evaluated the values of the ME and the NE, where the silage containing the youngest forage harvested presented the highest (P<0.05) values. The ME and NE values ranged from 1.43 to 1.90 Mcal/kg of dry matter and from 0.62 to 0.97 Mcal/kg of dry matter, respectively. The methane production by the fermentation of the ensiled material did not differ (P>0.05) between the three treatments measured. In Chapter 5, with the semi-automatic in vitro technic of gases production, was observed that the accumulated gases production by the Brachiaria decumbens grass silage harvested at 56 days was higher than the others treatments at 24, 48 and 96 hours of incubation (P<0.05), and the same treatment had higher (P<0.05) degradability for the DM and the organic matter (OM) in all of the fermentation times evaluated. Already in the experiment of in situ degradability of nutritional components, was observed that the average ruminal disappearance of DM, OM, crude protein, NDF and ADF, after 96 hours of ruminal incubation, were higher (P<0.05) for the silage made with the plant harvested at 56 days ofregrowth. It was conclude that the best age to cut the Brachiaria decumbens grass for silage is at 56 days of growth.