Estabilidade aeróbia da silagem de capim-elefante cultivar BRS Capiaçu em dois teores de matéria seca e inoculada com cepas de Lactobacillus em cultura pura e mista

Abstract

Elephant grass, cultivar BRS Capiaçu, has desirable characteristics for silage production. However, when harvested for this purpose, the plant has a high moisture content and a low content of water-soluble carbohydrates (WSA), parameters that affect the silage microbiota during fermentation and, consequently, aerobic stability. The objective of this research was to study the microbiota associated with aerobic deterioration of elephant grass silages cv. BRS Capiaçu with two levels of dry matter (DM) and inoculated with strains of Lentilactobacillus hilgardii (CNCM I-4785 82), Lactiplantibacillus plantarum (CCMA 1394). The grass was harvested with two DM contents: low DM 16.8% and high DM 24.3%, and chopped with an approximate particle size of 19 mm. After cutting the grass, the forage was prepared with the following treatments: control, CCMA 1394 (Lactiplantibacillus plantarum) 8.62log UFC/g, CNCM I-4785 82 (Lentilactobacillus hilgardii) 8.86logUFC/g and a combination of CCMA 1394 + CNCM I-4785 82. Experimental silos (30L capacity plastic pumps) were used for ensiling and opened after 104 days of fermentation. Samples of approximately 2kg of silage were removed, placed in plastic bags and stored in a room with controlled temperature. In the center of a bag with 5kg of silage, a data logger was placed to record the temperature every 30 min. Stability was evaluated at times 0, 1, 3 and 6 days. Microbiological analysis, organic acids, alcohols and pH were made from an aqueous extract of the samples at each time. The addition of inoculants affected the yeast population (P<0.0001), the silages treated with Le. hilgardii, showed lower yeast count regardless of DM content and days of aerobic exposure. On the opening day of the silo (time 0), the silages with low DM, treated with La. plantarum, Le. hilgardii and the combination La. plantarum + Le. hilgardii, did not present aerobic spore-forming bacteria counts, unlike the control silage. In silages with lower DM, the pH values increased after 3 days of exposure, reaching 7.33 with 6 days of aerobic exposure. Silages with DM content of 24.3% had the highest concentration of acetic acid compared to silages with DM content of 16.8%, in all exposure times. Regarding aerobic stability, the treatments did not differ statistically. The CNCM I-4785 82 inoculant stood out for presenting a lower yeast count and lower temperature after exposure to air, thus the silage was better preserved throughout the days of aerobic exposure.