Spectral analysis of bovine grazing behavior on Neotyphodium coenophialum infested tall fescue

Abstract

Bovines spend less time grazing and have reduced intake when grazing endophyte-infected (E +), Neotyphodium coenophialum Glen, Bacon, and Hamlin ( 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 studied using spectral analysis to determine if grazing response differed due to endophyte presence. Two 0.81-ha paddocks, one containing E − Kentucky-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 during two 48-h periods in each year. Spectral analysis, a technique used to detect sinusoidal components in a time series, revealed that steers grazing E − fescue repeated grazing behavior in 12- and 6-h intervals 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 between 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 − fescue and that spectral analysis was valuable in describing grazing behavior.