Wilted elephant grass (Pennisetum purpureum Schum.) Silage made from plants cut at three maturity stages. I - Yield and composition of the forages

Abstract

The present study was carried out at Instituto de Zootecnia, SP, in order to evaluate the dry inatter (DM) yield. DM chemical composition of green and wilted herbage, as well as the ehemical composition of silages rnade from grecn and wilted herbage of elephantgrass (Pennisetum purpureum Sclium.) cv. €˜Guaçu€™. To determine DM yielti, fifteen 27.95-m² plots were harvested 01110 April at 56, 70, and 84 days of regrovvth after mowing on 16 Jan, 30 Jan, and 13 Feb 1997, respectively. Each plot received 100 kg N, 80 kg P₂0₅, and 100 kg K₂0 as (NH₄)₂S0₄, simple superphosphate, and KCI, respectively. Nitrogen and potassium were split-applied, one half mowing and the other half 28 days later. The trial was set up in a completely randomized design with five replieations per treatment. Sampling was done by clipping each plot entirely, as the plots were set in the middle ot' the pasture and thus there were no border effects. After weighing, the green herbage was subsampled for determination of DM concentration and yield, weights of leaf and stem fractions plus dead material. The plots used for silage making were staged on the same dates and received the same fertilization. Silages were made from both fresh and wilted herbage, whole and chopped plants, with whole plants being dehydrated for 24 h under field conditions. Chopped herbage was wilted in the sun for 4 h on a brick-floored area. Experimental silos were 150-L plastic drums. Before ensiling the material was samplecl and sent to the laboratory for determination of chemical composition, soluble carbohydrate concentration, and buffering capacitv. Trcatments consisted of ali possible combinations of three forage ages (maturities) and three types of forage (thus a 3 x 3 factorial). Dry matter yield increase with regrowth interval, with the best leaf:steni ratio obseved at 70 days. The wilting methods raised DM concentration satisfactorily and did not reduce soluble carbohydrate concentrations to the point wliere lactic fermentation was compromised.