Meta-analysis of endophyte-infected tall fescue effects on cattle growth rates

Abstract

The objective of this study was to quantitatively summarize literature reporting endophyte-infected (Neotyphodium coenophialum) tall fescue (Festuca arundinacea) effects on cattle ADG. This meta-analysis evaluated endophyte infection level, climate, and forage yield using a literature dataset of 138 treatments from 20 articles. Three infection level measurements were tested: endophyte infection as a percentage of infected tillers (E%); ergovaline concentration in ppb ([E]); and total ergot alkaloid concentration ([TEA]). Three types of climate variables were used: base values (temperature, humidity, and relative humidity), climate indices (heat index and temperature-heat index [THI]), and novel climate variables accounting for duration of climate effects. Mixed effect models, weighted by 1/SEM, including a random effect of study were built for each factorial combination of measurement method and climate variable group. Because many studies were missing SEM, two datasets were used: one containing only data with SEM reported and one that also included missing-SEM data. For the complete-SEM dataset (CSD), models were weighted by 1/SEM. In the missing-SEM dataset (MSD) the mean reported 1/SEM was assigned as the weight for all missing SEM treatments. Although 18 initial models were created (2 × 3 × 3 factorial approach), the backward stepwise derivation resulted in models that included only endophyte infection level, suggesting a negative relationship between infection level and ADG. The CSD models predicted ADG to decrease 39 and 33 g/d with each increase of 100 ppb of [TEA] and [E], and by 39 g/d for each increase of 10% E%. In the MSD dataset, predicted ADG decreased by 39 and 33 g/d with each increase of 100 ppb of [TEA] and [E], and by 47 g/d for each increase of 10% E%. All relationships reported had P < 0.05. After visual inspection of the data, piecewise regression was used to identify an infection threshold (IT) of 60 ppb [E] and 11 E%, where the effect of infection level was constant on either side of the IT. The ADG was 40% and 49% greater for infection levels below the IT for [E] and E%, respectively. Across THI values in the analysis, ADG decreases ranged from 11.2% to 45.0% for cattle grazing endophyte-infected tall fescue compared to non-ergot alkaloid endophyte infected tall fescue. Pasture E%, [E], and [TEA] have a negative relationship with ADG in growing cattle, and increasing temperature decreases ADG when infection level is greater than the IT.

Ergot alkaloids induce vasoconstriction of bovine uterine and ovarian blood vessels

“…The E+ seed contained a mixture of ergot alkaloids, with ergovaline and ergotamine being the most bioactive (Klotz, 2015b), while the E− seed contained only a trace level of ergovaline. A dietary concentration of 500 μg/kg ergovaline + ergotamine was chosen to induce toxicosis consistent with moderate environmental exposure (Liebe and White, 2018).…”

Comparison and Diet Preference of Novel Endophyte‐Infected Tall Fescue Cultivars

“…BarOptima and Duramax contained low concentrations of ergovaline as well, though the concentrations were 2-to >10-fold less than those for CTE+ KY31 (Fig. Ergovaline concentrations for BarOptima and Duramax were at or below thresholds reported for cattle by Liebe and White (2018) and were below thresholds suggested for cattle in Missouri (Cornell et al, 1990). Ergovaline concentrations for Estancia, Jesup, Martin2, Texoma, and E− KY31 were nil.…”

“…4). Liebe and White (2018) reported threshold ergovaline concentrations from 20 articles using meta-analysis; the authors concluded that cattle average daily gain decreased 33 g d −1 with each increase of 100 mg kg −1 of ergovaline concentration, and they reported a threshold ergovaline concentration of 60 mg kg −1 . 4).…”

“…Threshold ergovaline concentrations for cattle range from 200 mg kg −1 ergovaline in Missouri (Cornell et al, 1990) to 390 mg kg −1 in Kentucky (Aiken et al, 2009) to 475 mg kg −1 in Oregon (Aldrich-Markham et al, 2007). Liebe and White (2018) reported threshold ergovaline concentrations from 20 articles using meta-analysis; the authors concluded that cattle average daily gain decreased 33 g d −1 with each increase of 100 mg kg −1 of ergovaline concentration, and they reported a threshold ergovaline concentration of 60 mg kg −1 . Ergovaline concentrations for BarOptima and Duramax were at or below thresholds reported for cattle by Liebe and White (2018) and were below thresholds suggested for cattle in Missouri (Cornell et al, 1990).…”

“…Liebe and White (2018) reported threshold ergovaline concentrations from 20 articles using meta-analysis; the authors concluded that cattle average daily gain decreased 33 g d −1 with each increase of 100 mg kg −1 of ergovaline concentration, and they reported a threshold ergovaline concentration of 60 mg kg −1 . Ergovaline concentrations for BarOptima and Duramax were at or below thresholds reported for cattle by Liebe and White (2018) and were below thresholds suggested for cattle in Missouri (Cornell et al, 1990). Ergovaline concentrations for CTE+ KY31 were at or above these thresholds during each grazing event (Fig.…”