Effect of Green Silver Nanoparticles Synthesized via Phlomis cancellata Bunge Extract on in vitro Ruminal Fermentation

 The anaerobic microbial fermentative digestion of feedstuffs in the rumen is not efficient. The gases are considered as waste products of rumen fermentation and also pollutants of the environment. Recent studies indicated that some metal nanoparticles (NPs) were toxic to rumen microbial population and inhibit methane production in anaerobic conditions. Plant extracts can be used to produce cost effective and eco-friendly green nanoparticles. Phlomis cancellata Bunge with Persian names Gushbarre sefid has high medicinal value and antibacterial properties and distributed dramatically in Khorasan, Mazandaran and Golestan. Hence, there is potential of using bio-synthesized nanoparticles in ruminant nutrition. However, there is not enough information regarding the effect of green nanoparticles on runminal condition. Therefore, the present investigation was carried out to study the effect of green silver nanoparticles synthesized via Phlomis cancellata Bunge extract on rumen fermentation in vitro.

Synthesis of sliver nanoparticles was prepared by adding of 1 ml of the aqueous extract to 4.76 mM sliver nitrate solution (pH= 6.84) allowed to react at 77 °C for 24.79 min in the dark to minimize the photo activation of silver nitrate. The color change of solution from yellow to brown after 3 min of incubation is indicative of the bioreduction of Ag+ ions in the solution to Ag°. Effects of increasing the concentration of green silver nanoparticles synthesized via Phlomis cancellata Bunge extract (0, 125 and 250 µg/ml) on rumen fermentation were evaluated using in vitro gas production technique. Gas production volumes were recorded at 3, 6, 9, 12, 24, 48, 72 and 96 h of incubation and then gas production kinetic was estimated. The obtained data from gas production at 24 h after incubation were used for estimation of digestible dry and organic matter, metabolisable energy, short chain fatty acids, partitioning factor, microbial biomass production and microbial biomass production efficiency.

 The increasing level of green silver nanoparticles synthesized via Phlomis cancellata Bunge extract did not significantly affect in vitro potential of gas production and gas production rate. For the cumulative gas production, no significant difference was found among the treatments. The lowest and highest in vitro potential of gas production, gas production rate and cumulative gas production was recorded for treatments 3 and 1, respectively. Silver nanoparticles exhibit unique bacteriostatic and bactericidal properties. At the atomic level, silver has the ability to absorb oxygen and acts as an oxidation catalyst. Atomic oxygen absorbed on the silver surface reacts with the thiol groups surrounding the surface of bacteria and viruses and removes hydrogen atoms. The bacterium loses respiration ability by disruption of the so-called respiratory channel, which results in bacterial death. The apparent in vitro dry matter digestibility and organic matter digestibility and true in vitro organic matter digestibility, were not significantly affected by addition of green silver nanoparticles synthesized via Phlomis cancellata Bunge extract. Addition of green silver nanoparticles synthesized via Phlomis cancellata Bunge extract failed to affect metabolisable energy, short chain fatty acids, partitioning factor, microbial biomass production and microbial biomass production efficiency. However, the lack of significant effect of the synthesized silver nanoparticles on the digestibility may be due to factors such as concentration, surface capacity, size, and other properties of silver nanoparticles. For treatment 1, the cumulative gas production over 24 and 48 h was negatively correlated apparent in vitro dry matter digestibility and organic matter digestibility. There was significant negative correlation between apparent in vitro organic matter digestibility and partitioning factor with cumulative gas production during hours of incubation for treatments 2. No significant correlation was found between apparent in vitro dry matter digestibility and organic matter digestibility and partitioning factor with the volume of cumulative gas produced during different incubation hours in for treatments 3.

 Supplementing of green silver nanoparticles synthesized via Phlomis cancellata Bunge extract could modify the characteristics of gas production and fermentation parameters basal diet and reduce the side effects of the anaerobic microbial fermentation. However, additional microbial studies with different level of green silver nanoparticles are necessary to determine the mode of action. Additionally, further in vivo work is needed to assess the effect of green silver nanoparticles inclusion on animal performance when cattle are fed ingredients commonly used in beef feedlot or dairy diets.