SPECTRAL-ANALYSIS OF BOVINE GRAZING BEHAVIOR ON NEOTYPHODIUM-COENOPHIALUM INFESTED TALL FESCUE

Bovines spend less time grazing and have reduced intake when grazing e ndophyte-infected (E +), Neotyphodium coenophialum Glen, Bacon, and Ha mlin (comb. novo) Morgan-Jones and Gams vs. endophyte-free (E -) tall fescue (Festuca arundinacea, Shreb.). Because bovine grazing behavior follows series of repeatable cycles, cyclic grazing behavior was studi ed using spectral analysis to determine if grazing response differed d ue to endophyte presence. Two 0.81-ha paddocks, one containing E -Kent ucky-31 (KY-31) tall fescue and one containing E + KY-31 (100% tiller infection rate) were stocked with yearling Angus steers in the spring and summer for two years. Trained observers monitored steer behavior d uring two 48-h periods in each year, Spectral analysis, a technique us ed to detect sinusoidal components in a time series, revealed that ste ers grazing E -fescue repeated grazing behavior in 12- and 6-h interva ls while E + steers exhibited an additional 8-h cycle. Steers grazing E + fescue spent less time(P < 0.05) grazing and lying, and more time standing(P < 0.05), than E -steers for both years, Crosscorrelations b etween hourly grazing behavior and hourly solar radiation resulted in significant, negative correlations at lag = 0 for E + Steers and with correlations near zero for E - steers. We conclude steers grazing E fescue exhibited different grazing behavior from steers grazing E -fes cue and that spectral analysis was valuable in describing grazing beha vior. (C) 1997 Elsevier Science B.V.