Effects of red clover isoflavones on tall fescue seed fermentation and microbial populations in vitro

Abstract

Negative impacts of endophyte-infected Lolium arundinaceum (Darbyshire) (tall fescue) are responsible for over $2 billion in losses to livestock producers annually. While the influence of endophyte-infected tall fescue has been studied for decades, mitigation methods have not been clearly elucidated. Isoflavones found in Trifolium pratense (red clover) have been the subject of recent research regarding tall fescue toxicosis mitigation. Therefore, the aim of this study was to determine the effect of ergovaline and red clover isoflavones on rumen microbial populations, fiber degradation, and volatile fatty acids (VFA) in an in vitro system. Using a dose of 1.10 mg × L-1, endophyte-infected or endophyte-free tall fescue seed was added to ANKOM fiber bags with or without 2.19 mg of isoflavones in the form of a control, powder, or pulverized tablet, resulting in a 2 × 3 factorial arrangements of treatments. Measurements of pH, VFA, bacterial taxa, as well as the disappearance of neutral detergent fiber (aNDF), acid detergent fiber (ADF), and crude protein (CP) were taken after 48 h of incubation. aNDF disappearance values were significantly altered by seed type (P = 0.003) and isoflavone treatment (P = 0.005), and ADF disappearance values were significantly different in a seed × isoflavone treatment interaction (P ≤ 0.05). A seed × isoflavone treatment interaction was also observed with respect to CP disappearance (P ≤ 0.05). Eighteen bacterial taxa were significantly altered by seed × isoflavone treatment interaction groups (P ≤ 0.05), eight bacterial taxa were increased by isoflavones (P ≤ 0.05), and ten bacterial taxa were altered by seed type (P ≤ 0.05). Due to the beneficial effect of isoflavones on tall fescue seed fiber degradation, these compounds may be viable options for mitigating fescue toxicosis. Further research should be conducted to determine physiological implications as well as microbiological changes in vivo.

Endophyte-Infected Tall Fescue Affects Rumen Microbiota in Grazing Ewes at Gestation and Lactation

“…Lachnospiraceae can produce volatile fatty acids (VFA), whose metabolism may be influenced by changes in the bioavailability of the primary fermentation metabolites by mycotoxins ( 30 , 32 ). Foote et al ( 33 ) confirmed that ergovaline reduced rumen VFA concentrations, which provides further support that intake of highly endophyte-infected tall fescue impacts nutrient bioavailability, and potentially absorption, along with the resident microbiota ( 34 ). Moreover, members of the Prevotella genus and Clostridiales order relatively abundant in MA on d115 are reported as ergovaline degraders ( 17 ).…”

Effects of endophyte-infected tall fescue seed and red clover isoflavones on rumen microbial populations and physiological parameters of beef cattle1,2

“…Among several isoflavones in clover tissue, biochanin A inhibits Gram-positive hyper-ammonia-producing bacteria (HAB; Flythe and Kagan, 2010 ) and reduces ammonia production from ruminal bacteria at a concentration of 30 ppm of rumen volume ( Flythe et al, 2013 ). Biochanin A is also a selective inhibitor of certain amylolytic and cellulolytic bacteria ( Harlow et al, 2017a , 2018; Melchior et al, 2018 ). Aiken et al (2016) determined that when biochanin A was ruminally dosed into goats consuming endophyte-infected tall fescue seed, vasodilation, and return to normal blood flow rates was observed.…”

In vitro metabolism of red clover isoflavones in rumen fluid

“…Furthermore, inhibitory effects of red clover isoflavones on specific bacteria in the rumen were reported in recent studies. Melchior et al (2018), Harlow et al (2017 and Harlow, Flythe, and Aiken (2018) Moreover, the metabolic pathways of daidzein include production of equol and O-desmethylangolensin (O-DMA) as the end products of either dehydroxylation or C-ring cleavage of dihydrodaidzein and distinct bacteria are involved into those metabolic processes (Luca et al, 2019). So both the shift in the bacterial abundance and diversity as well as the shift in metabolic pathway from equol to O-DMA production could explain the very low levels of equol in concentrate-rich diet supplemented with high levels of isoflavones.…”