Effet of quebracho tannin on silage nutritive value, ergovaline concentration, and fermentation parameters of tall fescue with two dry-matter levels

Authors: GROTE, ALLY - University Of Arkansas; Nieman, Christine; THOMAS, IVAN - University Of Arkansas; COFFEY, KEN - University Of Arkansas; MUIR, JAMES - Texas A&M Agrilife; Klotz, James

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2023
Publication Date: 2/27/2023
Citation: Grote, A.J., Nieman, C.C., Thomas, I.R., Coffey, K.P., Muir, J.P., Klotz, J.L. 2023. Effet of quebracho tannin on silage nutritive value, ergovaline concentration, and fermentation parameters of tall fescue with two dry-matter levels. Agronomy. 13:694. https://doi.org/10.3390/agronomy13030694.
DOI: https://doi.org/10.3390/agronomy13030694

Interpretive Summary: Tall fescue [Schedonorus arundinaceus (Shreb.)] is a prominent forage in the United States because of its wide range of establishment and adaption, length of grazing season, and resistance to pests and harsh environmental conditions. Tall fescue can be harvested as hay, but frequent spring rains may prevent harvest before excessive maturity. Harvesting tall fescue as baleage may provide an advantage as the forage can be baled at moistures greater than hay (<20% moisture). Tall fescue has a symbiotic relationship with the fungal endophyte, Neotyphodium coenophialum, which produces ergot alkaloids. Ergot alkaloids are heavily concentrated in the seed with some presence in the leaf and stem tissue. Livestock that consume endophyte infected fescue have reduced performance and reproductive efficiency. Fresh tall fescue generally contains the greatest ergovaline concentrations, tall fescue silage can contain similar concentrations of ergovaline, enough to induce tall fescue toxicosis. Some authors have suggested that ergovaline can be bound by condensed tannins, rending them ineffective. Condensed tannins, such as quebracho tannin [Schinopsis quebracho-colorado (Schltdl.) FA Barkley & T. Meyer], are polyphenolic compounds synthesized by plants. Condensed tannins bind to proteins and may also bind to the nitrogenous components of ergot alkaloids. Condensed tannins have also been reported to reduce plant protein degradation into non-protein nitrogen during the ensiling process without affecting the overall fermentation of silages as measured by pH and lactic acid concentrations. The objective of this study was to determine the effect of added quebracho tannin on tall fescue silage nutritive value, ergovaline concentrations, and fermentation parameters. Tall fescue ensiled with quebracho tannin at concentrations of 10 and 20 g/kg of silage DM had few effects on nutritive and fermentation parameters. Ergovaline concentrations were slightly decreased or remained the same after fermentation, regardless of moisture or quebracho tannin concentrations. Effects of quebracho tannins were limited, though tall fescue ensiled with up to 20 g/kg of silage DM of quebracho tannin reduced proteolysis regardless of moisture concentrations, without affecting other fermentation parameters. Quebracho tannin inclusion at 10 and 20 g/kg DM did not reduce ergovaline concentrations and whether condensed tannins bind to ergovaline in silage requires further examination with consideration to silage pH, and condensed tannin and ergovaline concentrations.

Technical Abstract: Tall fescue (Schedonorus arundinaceus (Shreb.) Dumort) is a cool-season forage grown in the mid-south United States of America that has the potential for spring silage. Ergovaline produced by the fungal endophyte Neotyphodium coenophialum is preserved in tall fescue silage and can induce tall fescue toxicosis in livestock. Condensed tannins, such as quebracho (Schinopsis quebracho-colorado (Schltdl.) F.A. Barkley and T. Meyer) extract, can bind to the nitrogenous components of ergovaline, rendering it ineffective in the ruminant. Quebracho tannin (QT) can also bind to crude protein, reducing its conversion to ammonia. Quebracho tannin was either not added (0QT) or added at 10 (10QT) or 20 (20QT) g/kg of dry matter (DM) of silage to chopped endophyte-infected tall fescue of 670 g/kg of moisture (high moisture, HM) and 440 g/kg of moisture (low moisture, LM). A moisture x QT interaction affected the final pH (p = 0.02), with the lowest pH observed in HM silages with 0QT and 10QT. The ergovaline concentrations were not significantly different (p = 0.19) among the post-ensiled forages. Ammonia concentrations (g/kg DM) were affected by a moisture x QT interaction (p = 0.05), with greater concentrations observed in HM 0QT compared with HM 10QT, HM 20QT, and LM 20QT. Lactic acid concentrations (g/kg DM) decreased (p = 0.05) with the addition of QT. The moisture x QT interaction (p = 0.02) resulted in higher concentrations of acetic acid in the HM silages with 0QT and 20QT compared to the LM silage with 20QT. The total acid concentrations (g/kg DM) were higher (p < 0.01) at HM but did not differ (p = 0.54) across the QT concentrations. Ensiling tall fescue with quebracho tannin did not reduce the ergovaline concentrations, although proteolysis was reduced at the inclusion of 10 g/kg of QT in the HM silages and 20 g/kg of QT in the LM silages. The results indicate that QT as a tall fescue silage additive showed promise for modifying silage characteristics but it did not reduce ergovaline concentrations at the low QT levels used in this study.