Producción de metano in vitro y parámetros fermentativos de mezclas de ensilado de girasol silvestre y pasto elefante, inoculadas o no con cepas de bacterias ácido-lácticas epífitas

The present investigation was carried out to determine the extent of the incorporation of Tithonia diversifolia (TD) and the possibility of blending it with Pennisetum purpureum (PP) to obtain the maximum benefit for ensilability and for animal nutrition. Silage mixtures of wild sunflower (TD) and elephant grass (PP) were evaluated based on chemical composition, quantification of gas production, methane release and fermentation parameters. The silage blends were arranged in four T. diversifolia / P. purpureum proportions, namely: 100/0; 67/33; 33/67; and 0/100 (fresh weight). Silages with higher proportions of T. diversifolia increased crude protein content, in vitro digestibility while decreasing NDF and ADF fractions (P<0.05). High amounts of T. diversifolia showed the lowest gas production values (160.2 ml), while treatments with higher grass inclusion produced a greater amount of gas up to 194.5 ml. Methane production was higher by increasing the proportion of P. purpureum into the silage blends. The silage inoculum did not have any impact on in vitro gas production (P<0.05). Also, higher proportions of T. diversifolia reduced acidification process while P. purpureum inclusion facilitated lower pH values. Lactic acid bacteria inoculum tended to decrease pH of silages but no clear effects on silage temperature were observed. Silages with high proportions of T. diversifolia (67 % of inclusion) would be more palatable for animals and might also translate into larger animal performance due to greater protein supply and better digestibility than silages with larger proportion of P. purpureum (67 and 100 % of inclusion).