Effect of using organic acid and alcoholic extract of propolis on chemical composition, aerobic stability, microbial population and gas production parameters of barley silage in ruminant nutrition

A study was conducted to evaluate the effect of addition alcoholic extract of propolis and organic acid (acetic acid) on chemical composition, fermentation characteristic and gas production parameters of barley silage in a complete randomized design. Whole crop barley was harvested and chopped with a conventional forage harvester under farm condition to length of 2-3 cm. Representative of barley forage samples were packed manually, in triplicate into plastic bags and were stored at ambient temperature and allowed to ensile for 1, 3, 7, 21 and 45 days. The following treatments were applied to the forage samples: 1) barley silage without any additives (control), 2) control + alcoholic extract of propolis (500 µl/kg of fresh forage) and 3) control + acetic acid (1% of DM).Results showed that there were differences among treatments on DM content and pH (p < 0.05). The highest and lowest pH was related to barley silage treated with organic acid and control treatment, respectively. Compared with control treatment, barley silage treated with acetic acid and alcoholic extract of propolis improved (40 and 18 h, respectively) aerobic stability (p < 0.05). The fungi count was lowest in organic acid treatment on days 3 and 7 (p < 0.05). However, the fungi population was not observed on days 21 and 45 after ensiling in all treatments. Organic acid treated barley silage had highest gas production potential and in contrast, using alcoholic extract of propolis increased ME, OMD and SCFA content. Generally, obtained results showed that although organic acid and alcoholic extract of propolis as additives had not considerably effect on nutritive value of barley silage, but they improved aerobic stability (p < 0.05).