Qualidade das silagens de seis genótipos de sorgo (Sorghum bicolor (L.) Moench) em diferentes estádios de maturação

In order to evaluate the quality of sorghum silages, six genotypes of this crop were cultivated and ensiled at three different times of harvesting. The genotypes evaluated were BR 601, BR 303, BR 304, AG 2006, BR 700 and BRS 701. The sorghum hybrids were ensiled in laboratory silos made of PVC tubes. Eighteen treatments, six hybrids in three different times of harvesting, with four repetitions were analysed in a totally randomized design. The original material was analysed for dry matter. At the opening of the silos, pH and ammonia nitrogen were determined and the silages were analysed for dry matter, crude protein and fibrous fractions. In all treatments, differences between the dry matter content in periods 1 and 2 and periods 1 and 3 were observed. Differences between hybrids (P<0.05) for dry matter content in the same period were also found. The lowest value was BR 601, period 1 (20.8%), and the highest was BR 304, period 3 (49.1%). The pH values achieved were between 3.6 and 3.9. Significant differences (P<0.05) between treatments and periods of harvesting were observed. In all treatments, the silages presented good fermentation patterns based on ammonia nitrogen content. The BR 601 showed the lowest value of crude protein (5.6%) and the highest value was shown by BR 304 (8.4%). In all hybrids the silages showed good fermentation patterns and were considered of good quality. The fibrous fraction content did not change with the age of the plant. All hybrids must be ensiled at the early-dough stage, except for BR 601 that must be ensiled at the late-dough stage.