Parâmetros bromatológicos e microbiológicos de silagens do terço superior da rama de mandioca (Manihot esculenta Crantz)

Abstract

This work aimed to evaluate the bromatological composition, and in vitro digestibility (IVD), by verifying the losses related to the fermentative process and microbiology of silages of the upper third of the cassava branch (SUTCB) of 4 cultivars, at 2 cutting ages (8 and 18 months) and 2 storage times (28 and 56 days). The cultivars used were BRS399, BRS420, BRSCS01, and IPR Paraguainha. The analyses related to the quality of the fermentation process and microbiology were performed on the samples in natura and at two ensiling times. The bromatological and digestibility analyses were carried out at the two silos' opening times. In the evaluation of losses resulting from the process, the means obtained for the variables were significant (P<0.001) for the isolated factors, such as cultivar, cutting age, and storage time. The bromatological and digestibility analyses were carried out at the two silos' opening times. In the evaluation of losses resulting from the process, the means obtained for the variables were significant (P<0.001) for the isolated factors, such as cultivar, cutting age, and storage time. The gas loss was 0.22% and 0.30% and effluent loss was 29.47 and 10.95 kg/ton DM for the cutting ages of 8 and 18, showing a difference between these treatments. There was a reduction in pH in plants ensiled at 18 months in relation to 8-month-old plants, as these have greater buffer capacity than those. There was a decrease (P<0.001) of undesirable microorganisms with time. The development of lactic acid bacteria (LAB) showed an increasing linear effect until 56 days of storage, being 5.18, 7.12, and 7.15 log CFU/g. The NDF content observed for averages obtained in the cutting age factor was 52.874% and 76.810% for the cutting ages of 8 and 18 months respectively. Corroborating with the values obtained for NDF, the content of ADF, cellulose, and lignin showed similar results, pointing to lower quality of plants harvested at 18 months. The content of CP presented was 13.09% and 8.70% for ages 8 and 18 months, indicating a higher leaf composition of the material harvested at younger ages. The in vitro digestibility of NDF for the cutting ages of 8 and 18 months were 67.16% and 54.73%. The results obtained showed superior bromatological composition for plants harvested at 8 months, without this interfering negatively in the fermentative process. The ensiling time of 56 days consolidated higher LAB counts. Therefore, the in vitro digestibility tests allowed us to conclude that SUTCB at 8 months can be considered an alternative food to be used in ruminant rations.