Cinética de fermentação das silagens e dos fenos de diferentes frações da parte aérea de variedades de mandioca pela técnica in vitro de produção de gases

Abstract

The objective of this work was to determine kinetics of fermentation of dry matter by means of in vitro technique of gas production of silagens and hays of different fractions of shoots of four varieties of cassava. The experiment was conducted in a completely randomized design with four replications, arranged in a 4 x 3 factorial design, being four varieties of cassava (Amarelinha, Sabará, Olho Roxo and Periquita) and three fraction of shoots (superior third, planting surpluses and whole plant). Part of the material was ensiled in mini-silos of PVC, being opened after 56 days of fermentation and another part was submitted to pre-dry to produce hay. Samples of silage and hay were collected and submitted to pre-dried, ground and then proceeded to essay of in vitro gas production. The pressure readings of gases produced during fermentations were performed at 0, 2; 4; 6; 8; 10; 12; 15; 18; 21; 24; 30; 36; 48; 72 and 96 hours after the beginning of incubations. Pressure readings of gases were made by means of pressure transducer and subsequently adjusted to volume of gases. The silage of Amarelinha and Periquita varieties, both in the superior third, showed the lowest rate of fermentation. The cumulative gas production was higher for silage of superior third for all of the varieties in the early days of incubation. Silages had no significant effect (P> 0.05), depending on the varieties, as for the parameters Soluble fraction (A) and potential fermentable insoluble fraction (B). The highest DM degradability for hay also occurred in the early days of incubation. Hays of superior third for variety Amarelinha showed potential and effective degradability of DM higher than the other varieties and fractions of shoots. The hay of the superior third of the variety Olho Roxo has the highest concentration of soluble substrates, low time of colonization and higher rate of gas production indicating better nutritional value.