Soybean-sorghum mixture and soybean treated with molasses effects on quality and silage fermentation

Abstract

Soybean [Glycine max (L.) Merr.] harvested at R6 phenological growth stage (PGS) and ensiled [treated with 6% molasses, and 50:50 soybean-sorghum mixture (SSOR)] were assessed. Treatments were ensiled in 15-L micro-silos and sampled after 30-d of fermentation. The soybean-sorghum mixture (SSOR) had highest DMY (4.0 Mg ha^-1) and mean values of 32% dry matter (DM), 16% crude protein, 54% total digestible nutrients, 1.13 Mcal net energy for lactation (NEL) kg^-1 DM and 103 RFV. These values were lower ((p0.05) than those obtained for soybean alone (S) and soybean with molasses (SM). Highest neutral detergent fiber was observed in SSOR (56%), but difference in acid detergent fiber (35%). The SSOR had mean values of 4.13, 7.82, 2.88, 0.03 and 8.25, pH, and percentage lactic, acetic, butyric and NH₃-N, respectively.  Silage pH, lactic acid, and NH₃-N values of SSOR were different (p 0.05) from both soybean alone and soybean treated with molasses, but acetic acid and butyric acid content differed only relative to soybean (sole crop). As for aerobic stability, there were differences (p0.05) between treatments in pH, with values of 4.75, 4.35 and 4.04 for soybean, soybean-molasses, and SSOR, respectively. However, SSOR silage had the highest (p 0.05) temperature and loss of DM.  There was a quadratic relationship (p0.05) between time of exposure and temperature of the silage. Adding molasses and a mixture with sorghum improved (p0.05) fermentation characteristics of soybean silage on pH, organic acids, ammonium equivalent protein (AEP) and NH₃-N. From a nutritional standpoint, the addition of molasses appears to be the best option for soybean silage preparation, because it does not adversely affect CP, ADF, NDF nor energy level (TDN and NEL). However, if maximum forage yield is desired the SSOR mixture may be more advantageous.