Avaliação agronômica e nutricional de genótipos de sorgo mutantes BMR e normais utilizados para corte e pastejo

Abstract

The experiment was carried out at Embrapa Milho and Sorgo in Sete LagoasMG in order to evaluate the agronomic and nutritional characteristics of genotypes of sorghum BMR mutant and normal one used for cutting and grazing. Twenty sorghum genotypes were used, being eleven mutant BMR and nine normal ones. The plantation was in blocks at random, with three blocks in which each genotype was a treatment, totalizing 60 experimental parcels. The agronomic and nutritional characteristics were analyzed in the second cutting at 42 days after the first one. The evaluated agronomic characteristics were height, production of green matter and dry matter, number of lodged plants and broken plants. For nutritional analysis, the samples were cut, pre dry, worn out and stored in polyethylene containers, being determined content of dry matter, ether extract, ashes, crude protein, neutral detergent insoluble nitrogen, acid detergent insoluble nitrogen, neutral detergent fiber, acid detergent fiber, non fiber carbohydrates, total carbohydrates, hemicellulose, cellulose and lignin. The data were submitted to analysis of variance through SISVAR, and for comparing the means was used Scott-Knott’s test (p<0.05). In relation to height, production of green matter and dry matter, there was difference (p<0.05) between the genotypes; for height, average values oscillated from 1.28 m for CMSXS156AxTX2785bmr to 1.72 m for IS10428xTX2784; concerning to green matter yield, average values varied from 12.00 t ha-1 for CMSXS157AxTX2785bmr to 18.93 t ha-1 for IS10428xTX2784; in relation to production of dry matter, the average values varied from 1.23 t ha-1 for CMSXS156AxTX2784 to 2.29 t ha-1 for IS10428xTX2784. As for dry matter, ether extract, ashes, neutral detergent unavailable nitrogen, acid detergent unavailable nitrogen, neutral detergent fiber, acid detergent fiber and hemicellulose, there was no difference (p>0.05) between the genotypes, the means were 11.87; 1.35; 6.27; 1.30; 0.23; 58.08; 35.28 and 22.73%, respectively. In relation to crude protein, there was difference (p<0.05) between the genotypes, the average contents varied from 9.77 for BR001AXTX2785bmr to 16.45 for BR001AxTX2784. Concerning to total carbohydrates and non fiber carbohydrates, there was difference (p<0.05) between the genotypes; as for total carbohydrates, the average contents varied from 75.21% for BR007AxTX2785bmr to 83.28% for BR001AXTX2785bmr; for non fiber carbohydrates the average contents oscillated from 17.46% to 25.51% for CMSXS156AxTX2785bmr and IS10428xTX2784, respectively. Concerning to cellulose and lignin, there was difference (p<0.05) between the genotypes; for cellulose the average contents varied from 22.30% for IS10428xTX2784 to 27.94% for TX635AxTX2785bmr; as for lignin, average contents were from 3.08% for BR007AxTX2785bmr to 7.31% for BR001AxTX2784. The genotypes IS10428xTX2784 and BR007AxTX2784, according to evaluated agronomic and nutritional characteristics, are the most indicated to be used in the feeding of ruminants in the conditions of accomplishment of this experiment.