Effect of different additives on chemical composition, fermentation parameters, digestibility and gas production of Gundelia tournefortii silage

Intake of poor quality plants of rangelands and pasture grasses and agriculture by products by ruminants is usually low to maintain animal performance because of their poor digestibility and nutrient deficiency. So, it seems essential to explore new feed resources, which may have potential as an animal feedstuff. So, one possible way to reduce this alimentary deficit is to use of naturally growing forages including Gundelia tournefortii (G. tournefortii). G. tournefortii is one of the most important rangeland plants that can be used to feed livestock. G. tournefortii are known to be a plant with high nutritional value and water content, and are therefore likely to be highly selective for consumption by native herbivores. It is very resistant to cold and dry weather and tolerates high temperature changes. Therefore, due to their diversity, they are able to propagate in large ecological areas and can be dry and semi-arid areas, often as part of forage and even a relatively good source of protein for ruminants. The aim of this study was to evaluate the effect of adding different additives on chemical composition, fermentation characteristics, gas production and digestibility parameters of G. tournefortii silage in a completely randomized design.

Whole forage Gundelia tournefortii were harvested and chopped with a conventional forage harvester under farm condition to length of 3-4 cm. Representative of Gundelia tournefortii forage samples were packed manually, in triplicate into plastic bags. The filled silos were stored at ambient temperature and allowed to ensile for 3, 7, 21 and 45 days. The following treatments were: 1) Gundelia tournefortii silage without any additives (control), 2) control + molasses (5% of DM), 3) control + organic acid (1% of DM), 4) control + barley meal (10% of DM) and 5) control + barley silage (20% of DM). After designated ensiling times, silos were opened and the ensiled forage was mixed thoroughly and then were dried at a 60°C in oven for 48 h and then ground to pass through a 2 mm screen for later analysis.

Results showed that different additives had effect on chemical composition of G. tournefortii silage significantly (p<0.05). Treatment G. tournefortii + barley meal had highest dry matter (DM) and organic matter (OM) content compared with others. Fermentation characteristics of silage were affected by different additives (p<0.05) and G. tournefortii treated with molasses had lowest pH. The highest and lowest aerobic stability was observed in organic acid treated silage (42 h) and barley treated silage (31/5), respectively. There were significantly differences among treatments on gas production parameters (P<0.05) and barley meal treated silage (on day 3) had highest gas production potential, organic matter digestibility (OMD) and short chain fatty acid (SCFA). In vitro digestibility of DM and OM were affected by additives (P<0.05). Treatment control (on day 7) had highest partitioning factor, and microbial crud protein efficiency.

Overall, these results indicated that in vitro gas production and digesibilty of G. tournefortii silage were improved by the application of molasses and barley silage as additive and its aerobic stability was improved by using acis asetic.