Avaliação agronômica e nutricional da rebrota anual de quatro genótipos de sorgo para produção de silagem na região Norte de Minas Gerais

Abstract

The experiment was carried out at Experimental Farm of UNIMONTES in Janaúba, north of Minas Gerais, in order to determine the agronomic and nutritional features of the regrowth of sorghum genotypes for the production of silage. The used genotypes were Volumax, AG2005E, and Qualimax BRS610. The planting was done in randomized blocks in the field, with five replicates per genotype and two experimental conditions (sorghum sown in the year and annual regrowth) in a 4x2 factorial. The evaluated agronomic characteristics were regrowth rate, number of plants per hectare, number of lodged plants, number of broken plants, plant height, production of green matter and dry matter, proportion of stems, leaves and panicles. After cutting, part of the material was ensiled. After opening the silos, the samples were pre-dried, ground and packed in glass bottles for analysis of dry matter, crude protein, neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose, cellulose and lignin, pH, NH3/NT and in vitro digestibility of dry matter. Values of Pl N / ha were higher in regrowth compared to sorghum of the year. In relation to GMP / ha, DMP / ha and DDM / ha the highest productions were observed in sorghum of the year. The average height ranged from 1.77 to 2.35 m, being the tallest plants found in sorghum of the year. For the experimental conditions, the highest percentages of leaf were observed for sorghum of the year. As for the panicle percentage, the production was the same in both experimental conditions. The highest percentages of stem were observed in regrowth. The rate of regrowth was similar (p> 0.05) for all of the genotypes. The DM contents were similar in regrowth and sorghum of the year. The CP values for the silage in both conditions showed some difference only for the AG 2005E and the BRS 610, and the highest levels were observed for sorghum of the year. In assessing the values of NDF of silage in different conditions, there was difference (p 0.05) for both experimental conditions. In assessing the values of HCEL in different conditions, there was difference (p< 0.05) only for the Qualimax genotype. The values of CEL ranged from 24.71 to 27.33%, not differing (p>0.05) in experimental conditions. As to LNG, in the experimental conditions, there was difference only for BRS610. The highest percentages of the IVDDM in silages were found in sorghum of the year. The pH levels, NH3/NT, lactic acid and acetic acid in silages were satisfactory for a good profile of ferrmentation. The evaluated genotypes as in the regrowth as in sorghum of the year present potential for silage production by having appropriate, productive, nutritional and fermentative characteristics. The rates of regrowth were sufficient to prove that the root system of sorghum remained alive in the field, allowing to obtain good quality silage. Thus, the regrowth of sorghum may be an alternative for the silage production.