Ginkgo fruit extract as an additive to modify rumen microbiota and fermentation and to mitigate methane production

Abstract

Ginkgo fruit, an unused byproduct of the ginkgo nut industry, contains antimicrobial compounds known as anacardic acids. Two major cultivars of ginkgo, Kyuju (K) and Tokuro (T), were evaluated for their potential as a feed additive for ruminants. In batch culture, we incubated a mixture of hay and concentrate in diluted rumen fluid with or without 1.6% (fruit equivalent) ginkgo fruit extract. We conducted another series of batch culture studies to determine the dose response of fermentation. We also conducted continuous culture using the rumen simulation technique (RUSITEC) with cultivar K and carried out a pure culture study to monitor the sensitivity of 17 representative rumen bacterial species to ginkgo extract and component phenolics. Although both K and T extracts led to decreased methane and increased propionate production, changes were more apparent with K extract, and were dose-dependent. Total gas production was depressed at doses ≥3.2%, suggesting that 1.6% was the optimal supplementation level. In RUSITEC fermentation supplemented with 1.6% ginkgo K, methane decreased by 53% without affecting total gas or total VFA production, but with decreased acetate and increased propionate. Disappearance of dry matter, neutral detergent fiber, and acid detergent fiber were not affected by ginkgo, but ammonia levels were decreased. Quantitative PCR indicated that the abundance of protozoa, fungi, methanogens, and bacteria related to hydrogen and formate production decreased, but the abundance of bacteria related to propionate production increased. MiSeq analysis (Illumina Inc., San Diego, CA) confirmed these bacterial changes and identified archaeal community changes, including a decrease in Methanobrevibacter and Methanomassiliicoccaceae and an increase in Methanoplanus. Pure culture study results supported the findings for the above bacterial community changes. These results demonstrate that ginkgo fruit can modulate rumen fermentation toward methane mitigation and propionate enhancement via microbial selection.

Effect of ginkgo extract supplementation on in vitro rumen fermentation and bacterial profiles under different dietary conditions

“…This may be the reason for the least methane reduction with the 1:9 ratio (14.6%, Table 2). A previous study (Oh et al 2017) reported that ammonia was decreased by ginkgo extract in the artificial rumen, possibly by inhibiting hyper-ammonia producing bacteria such as Peptostreptcoccus anaerobious, Clostridium aminophilum, Clostridium sticklandii (Chen & Russell 1989). The effect of dietary ginkgo extract supplementation on rumen ammonia was not clear (Table 2).…”

“…higher propionate and lower methane production) as a result of microbial selection (Oh et al 2017). higher propionate and lower methane production) as a result of microbial selection (Oh et al 2017).…”

“…The presence of anacardic acid, cardanol and cardol in the ginkgo extract was determined by high-performance liquid chromatography (HPLC) (Watanabe et al 2010). SCFA sample preparation and gas chromatographic determination were the same as previously described (Oh et al 2017). SCFA sample preparation and gas chromatographic determination were the same as previously described (Oh et al 2017).…”

“…The ginkgo cultivar Kyuju was selected as the source material, as it was previously identified to be a more potent modulator of rumen fermentation than Tokuro, another main cultivar (Oh et al 2017). The ginkgo fruit was physically mashed and separated using a hand-made machine, and sampled at a private ginkgo farm in Sobue, Aichi Prefecture, Japan, which is a major ginkgo nut producing area.…”

“…Recently, phytogenic compounds as novel sources of feed additives have been investigated based on the fact that plants produce a large variety of metabolites, and the use of these natural sources may not be subject to concerns raised regarding the overuse of chemically synthesized antibiotics (Cowan 1999). More recently, ginkgo fruit, which contains antimicrobial phenols such as anacardic acid, was applied to modulate fermentation in an artificial rumen including methane mitigation (Oh et al 2017). The functionality of this candidate additive was assessed in a fixed single dietary regimen and ginkgo fruit extract was found to select for rumen microbes, thereby altering fermentation toward more propionate and less methane production.…”