Abstract
Tall fescue (Schedonorus arundinaceus) is a cool-season perennial grass that is widely used as a forage for many livestock species including sheep. An endophyte (Neotyphodium coenophialum) in tall fescue produces ergot alkaloids that enhance plant survival but produce toxicosis in animals. The objective of this study was to investigate the rumen microbiota from gestation and lactation in ewes grazing tall fescue pastures with high (HA) or moderate (MA) levels of endophyte infection, and their relationship with serum parameters. Data were collected at the beginning of the study (d1), the week before initiation of lambing (d51), and at the end of the trial (d115). The rumen microbiota was evaluated using 16S rRNA gene sequencing. Ewes grazing HA had greater serum non-esterified fatty acid (NEFA) (P = 0.024) levels compared with ewes in MA pasture at d115. Both the number of observed OTUs and Shannon diversity index tended (P = 0.08, P = 0.06) to be greater for HA than for MA on d115. At the genus level, Prevotella relative abundance increased with time in both MA and HA (on d1, d51, and d115: 15.17, 25.59, and 24.78% in MA; 14.17, 18.10, and 19.41% in HA). Taxa unclassified at the genus level including (unclassified) Lachnospiraceae, Coriobacteriaceae, and Veillonellaceae exhibited higher abundances in HA at d51 (3.72, 2.07, and 11.22%) compared with MA (2.06, 1.28, and 7.42%). The predictor microbiota for HA and MA were identified by a random forest classification model. The HA predictors included bacteria associated with unclassified Coriobacteriaceae and Ruminococcaceae. Other OTUs classified as Prevotella and Clostridiales could be microbial predictors for MA. The OTUs classified as Prevotella and Lachnospiraceae were negatively correlated with serum concentration of prolactin. Negative correlations with NEFA were observed in the microbiota such as species affiliated to unclassified Clostridiales and Prevotella. OTUs classified as Bacteroidetes and Coriobacteriaceae exhibited a positive correlation with NEFA. Our study confirmed that the rumen microbiota populations were affected by high levels of toxins in endophyte-infected tall fescue and were associated with host hormone and energy metabolism.
Highlights
Tall fescue [Schedonorus arundinaceus (Schreb.) Dumort, syn
One of the most common classes of mycotoxins associated with N. coenophialum include ergot alkaloids, in which toxicity is typically characterized within livestock by reduced weight gain and volatile fatty acid absorption, restricted blood flow, and reduced reproductive rates [7, 8]
Concentration of ergovaline and total ergot alkaloids changed over time, they were greater in HA than MA throughout this study
Summary
Tall fescue [Schedonorus arundinaceus (Schreb.) Dumort, syn. Festuca arundinacea] is a cool-season perennial grass that has been widely used as a forage for livestock [1]. Ergovaline is the main ergopeptine alkaloid produced in the endophyte-infected tall fescue, and is considered the primary causative agent of fescue toxicosis in livestock [9, 10]. Ergot alkaloids contain a tetracyclic ergoline ring and are structurally similar to biogenic amines such as serotonin, dopamine, norepinephrine, and epinephrine [11]. This structural confirmation enables the compound to ligate receptors for biogenic amines, which have been hypothesized to decrease serum prolactin (PRL) concentrations and induce vasoconstriction via downstream signaling events [12, 13]. The EC50 dose of ergovaline is relatively low, and can induce a series of adverse reactions in animals, such as the reduction of feed efficiency and gastrointestinal passage rates [7]
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