Fungal Endophyte Infection‐Loline Derivative Alkaloid Concentration of Grazed Tall Fescue1

Abstract

AbstractImpaired animal performance on tall fescue (Festuca arundinacea, Schreb.) pasture has been associated with the presence of a fungal endophyte (Acremonium coenophialum). A number of alkaloids, including the loline derivatives N‐formyl and N‐acetyl loline, occur in endophyte infected tall fescue. A study was conducted at Watkinsville, GA, on a Cecil sandy loam (Typic hapludult) to examine the influence of N fertilization and season on endophyte infection frequency (EIF) and loline derivative alkaloid concentration (LDA) of grazed low and high endophyte tall fescue. Paddocks (0.7 ha) established with low and high endophyte status ‘Ky‐31’ tall fescue seed were fertilized with 134 and 336 kg N ha−1 (22 factorial) and replicated three times. Endophyte infection frequency was greater in high than low fungus paddocks during the 3‐yr study. Endophyte infection frequency means within a given paddock, i.e., high or low fungus, remained relatively constant in 1983 and 1984 but increased by 50% in high and 100% in low fungus paddocks in 1985. Endophyte infection frequency was not affected by N nor did infection frequency vary significantly within a growing season. Loline derivative alkaloid concentration and EIF were significantly correlated (positive) in each growing season. High fungus paddocks had significantly greater (100%) LDA than low fungus paddocks. The ratio of LDA to EIF was greater under high N and high fungus conditions in the fall of 1983 and in 1984. Periods of LDA production may be more closely associated with short‐term weather conditions than absolute EIF. The relationship between LDA and EIF may not be simply defined in continuously grazed tall fescue, especially under moderate EIF.