Características agronômicas e valor nutricional das silagens de cinco genótipos de sorgo cultivados no inverno

Abstract

The experiment was carried out in the Experimental farm of UNIMONTES in Janaúba, North of Minas Gerais, aiming at determining the agronomic and nutritional characteristics of the silages of five sorghum genotypes cultivated in the winter. The used materials were Volumax, AG2005E, Qualimax, BRS610 and AG2501. The planting was accomplished in blocks at random in the field, with four repetitions for genotype. The agronomic characteristics were assessed by the counting of number of plants per hectare, number of lodged plants, number of broken plants, height of the plant and through weighting it was evaluated the green matter yield, dry matter yield and stem proportions, leaves and panícula. After cutting, part of the material was ensiled. After the silos opening, the samples were pre-dried, ground and conditioned in glass flasks for analyses of dry matter, crude protein, neutral detergent fiber (FDN), acid detergent fiber (FDA), hemicellulose, cellulose and lignin by the sequential method; pH, NH3/NT and dry matter digestibility in vitro. The values of NºPl/ha were superior in the genotype AG2501 for being of the type cut and grazing. The medium values of height varied from 1,63 to 2,40 m. Concerning to GMY /ha and DMY/ha, the largest productions were observed in the BRS610, Volumax and AG2005E genotypes. In the leaves percentile, AG2005E overcame all the others. As for the percentile of panicle, the BRS610, AG2005E, Volumax and Qualimax genotypes were similar overcoming the AG2501 one. The largest stem percentage was observed in the genotype AG2501. The DM contents were superior in the AG2501, BRS610 and AG2005E genotypes. For the values of CP of the silage, AG2005E overcame all the others ones. When analysing the NDF values of the silages, there was not significant difference between the genotypes. In relation to ADF, there was not difference (p>0,05) between the genotypes AG2501, Volumax and AG2005E that it overcame the others ones. When was analysed the values of HCEL there was not statistical difference (p>0,05) between the genotypes AG2501, Volumax and AG2005E that it overcame the others ones. When was analysed the values of HCEL there was not statistical difference (p>0,05) between the genotypes. The values of CEL varied from 25,69 to 28,45. In relation to LGN, the BRS610 genotype overcame all the others ones. The pH values, NH3/NT, lactic acid and acetic acid of the silages were satisfactory for a good fermentation profile. The largest percentages of DIVDM of the silages were found in the Qualimax, BRS610 and AG2005E genotypes that did not differ amongst themselves and they were superior to the others. The data were submitted to variance analyses through the SISVAR program and the comparisons of averages were made in agreement with Scott-Knott test at the level of 5%. The studied genotypes presented good green mass yield and also agronomic characteristics and nutritional value appropriated to production of silages with good fermentative pattern when cultivated in the winter.