Seleção de genótipos de sorgo forrageiro para ensilagem: características agronômicas, parâmetros fermentativos e valor nutritivo

Abstract

Forage production in Brazil, especially in semi-arid regions, faces limitations imposed by irregular rainfall and climatic stresses. Forage sorghum (Sorghum bicolor) presents itself as a viable alternative due to its adaptability to water deficit and low soil fertility. The development of new, more productive genotypes with higher nutritional value represents an important advancement in improving forage production efficiency, making it essential to evaluate them for agronomic performance and silage quality. In this study, 18 genotypes (14 experimental hybrids and 4 commercial ones) were analyzed in two experiments conducted during the 2021/2022 and 2022/2023 growing seasons. In Experiment 1, the sorghum genotypes showed significant differences in agronomic characteristics. Plant height was higher in the first agricultural year, with genotypes 202110F005 to 202110F013 and CMSXS6000 to CMSXS6003 standing out, while BRS655 had shorter stature. There was a genotype-year interaction for plant number and flowering: BRS658 had a higher number of plants in the second year and CMSXS6002 was the latest to flower in both years. The leaf-to-stem ratio (LSR) was higher in genotypes BRS655, BRS658, and AGRI001E. The highest green matter productivity (GMP) in the second year was recorded by 202110F011, while the highest dry matter values (DMP) were obtained by 202110F007, 202110F011, 202110F012, 202110F013, and CMSXS6000. Multivariate analysis showed 202110F013 as the most productive and BRS655 with the lowest average values. In Experiment 2, the silages had an average pH of 3.66 and average aerobic stability of 127.4 hours, with no differences between genotypes. Ammoniacal nitrogen was higher in the silages of BRS658, CMSXS6001, and Volumax. Genotype BRS658 had the highest dry matter content (307.4 g/kg), crude protein (93.9 g/kg), and total digestible nutrients (614.2 g/kg), in addition to the lowest fiber contents. Volumax also demonstrated high nutritional quality. CMSXS6002 had a higher ash content. In ruminal kinetics, Volumax and BRS658 showed higher potential degradability of dry matter (649.5 and 639.3 g/kg) and lower indigestible fraction (350.5 and 360.6 g/kg). Regarding fiber, Volumax had the highest degradable fraction (526.5 g/kg) and lowest indigestible fraction (473.5 g/kg). Silages from genotypes 202110F007, 202110F008, CMSXS6000, and CMSXS6002 showed higher production of potentially degradable dry matter. It is concluded that the observed genetic diversity allows for the selection of materials with high productive and nutritional performance. The cross between 202110F011 and BRS655 is recommended. Genotypes such as 202110F007, CMSXS6000, and CMSXS6001 are indicated for environments with climatic variations due to their productive stability.