Fermentation quality, in vitro digestibility and aerobic stability of total mixed ration silages prepared with whole-plant corn (Zea mays L.) and hulless barley (Hordeum vulgare L.) straw

Abstract

This study was carried out to assess the effects of adding Lactobacillus plantarum, molasses or/and ethanol on the fermentation quality, in vitro digestibility and aerobic stability of total mixed ration (TMR) silage, which is well accepted in small-scale dairy farms in Tibet. Total mixed ration were ensiled in laboratory silos (1 L) and treated with (1) no additive (Control), (2) ethanol (E, 25 ml/kg fresh weight (FW)), (3) molasses (M, 30 g/kg FW); (4) Lactobacillus plantarum (L, 106cfu/g FW); (5) ethanol + molasses (EM); and (6) ethanol + Lactobacillus plantarum (EL). After 45 days of ensiling, six silos per treatment were opened for the fermentation quality and in vitro digestibility analyses, whereas 18 silos were used for the aerobic stability test for the following 9 days. All TMR silages were well preserved with dominant lactic acid (LA), low pH and ammonia nitrogen, and negligible propionic and butyric acid. The L and EL silages had the lowest pH and highest LA concentrations. The addition of ethanol did not inhibit silage fermentation as there were no significant differences for the pH, LA, acetic acid, negligible propionic acid or ammonia nitrogen content, lactic acid bacteria and yeast counts between Control and the E silage. During the aerobic stability test, pH increased by 1.39, 1.67, 1.69 and 0.74 for the Control, M, L and EM silages, but only 0.40 and 0.34 for E and EL silages, respectively. Upon exposure to air, the LA concentration in the L silage was evidently (P < 0.05) decreased, whereas LA concentration in the EL silage remained the highest value after the third day of aerobic exposure. Mean populations of aerobic bacteria and yeast in the E and EL silages were lower (P < 0.05) than those of the Control. These findings suggested that L. plantarum is effective in improving fermentation quality of TMR silages. Although the addition of ethanol in our study did not depress the fermentation of the TMR silages, it showed potential to inhibit the aerobic spoilage of TMR silages, either alone or in combination with the L. plantarum. It is concluded that L. plantarum combined with ethanol not only ensures better fermentation but also could improve aerobic stability.