Efeito de diferentes teores de matéria seca na conservação de mata-pasto (Senna obtusifolia)

Abstract

The use of legumes such as mata-pasto (Senna obtusifolia) has been encouraged in the semiarid region due to its adaptability and high biomass production. However, its high moisture content and low water-soluble carbohydrates concentration difficult its preservation via ensilage. This study aimed to evaluate the effects of different dry matter (DM) contents on the fermentative, chemical, and microbiological properties of mata-pasto ensilage. The experiment was conducted in a completely randomized design, with five DM contents: 22%, 35%, 45%, 55%, and 65%, with four replicates per treatment. Plastic buckets (10 L) were used as experimental silos and stored for 75 d. Variables related to chemical, fermentative, microbiological characteristics, and aerobic stability were evaluated. Data were subjected to analysis of variance, and a significant effect was considered at P < 0.05. There was a linear effect for DM (P < 0.001) and crude protein (CP; P = 0.001) concentrations, in which their concentrations increased as DM contents increased, with values between 22.1 – 65.3% for DM and 11.5-15.3% for CP. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) were not affected (P > 0.05) by DM. There was a quadratic (P = 0.006) adjustment for pH, with values between 4.89 and 5.46 and lower values observed in silages with 45 and 55% DM. There was a quadratic (P = 0.024) and linear (P < 0.001) adjustment for NH3-N concentration. A peak in NH3-N concentration was observed in silage with 35% DM (7,84% Total-N), reducing at 45% DM (5.21% Total-N), and increasing with 55 and 65% DM. There was a quadratic (P < 0.001) adjustment for dry matter losses (DML), with lower values observed with 45 and 55% DM (4.2 and 3.8%, respectively), and higher DML with 22 and 65% DM (8.9 and 5.7%, respectively). There was a linear adjustment (P = 0.002) for weight losses, where an increase in losses was observed as DM contents increased. A quadratic (P < 0.001) adjustment in silo density was observed as DM concentration at the time of ensiling was higher. Lower density values were obtained in forage ensiled with 65% DM 550 kg/m³). There was no effect (P > 0.05) on the aerobic stability. No changes were observed in microorganism counts, except for the Enterobacteriaceae count, where a reduction (P = 0.028) in the count was observed when DM contents increased. Ensiling with 45% and 55% DM provides better fermentation conditions, with lower DM, more adequate pH, less protein degradation, and greater stability.