GROWTH AND SUBSEQUENT FEEDLOT PERFORMANCE OF ESTRADIOL-IMPLANTED VS NONIMPLANTED STEERS GRAZING FALL-ACCUMULATED ENDOPHYTE-INFESTED OR LOW-ENDOPHYTE TALL FESCUE
Mg. Beconi et al., GROWTH AND SUBSEQUENT FEEDLOT PERFORMANCE OF ESTRADIOL-IMPLANTED VS NONIMPLANTED STEERS GRAZING FALL-ACCUMULATED ENDOPHYTE-INFESTED OR LOW-ENDOPHYTE TALL FESCUE, Journal of animal science, 73(6), 1995, pp. 1576-1584
A growing-finishing study using Angus steer calves was conducted in th
ree phases: 1) grazing stockpiled 'Kentucky-31' tall fescue (Festuca a
rundinacea Schreb.) with high (65%; HE KY-31) and low (0%; LE KY-31) i
nfestation rates of Acremonium coenophialum Morgan-Jones and Gams and
'Kenhy' and 'Johnstone' tall fescue with low (< 1%) infestation rate o
f Acremonium coenophialum from October 24 to December 19; 2) drylot fe
eding of Johnstone and HE KY-31 haylage (December 19 to April 10); and
3) feedlot finishing on a common high-concentrate diet (April 11 to A
ugust 1). In Phase 1, ADG was greatest (P < .05) for Kenhy, intermedia
te for Johnstone and LE KY-31, and lowest (P < .05) for HE KY-31. Impl
antation with estradiol 17-beta increased ADG (P < .01) by 23, 27, 7,
and 2% for steers grazing Johnstone, HE KY-31, LE KY-31, and Kenhy, re
spectively. Dry matter digestibility and DMI of stockpiled Johnstone a
nd HE KY-31 were not different (P > .10). During Phase 2, steers consu
ming Johnstone haylage had greater (P < .01) DMI, ADG, and gain:feed r
atio (G:F) than steers consuming HE KY-31 haylage. During Phase 3, ste
ers previously consuming Johnstone had greater DMI (P < .10); however,
steers previously fed HE KY-31 had greater ADG (P < .05) and G:F (P <
.01). By the end of the study, steer body weights were not different
(P > .10) between treatments. These data indicate that growth-decreasi
ng effects of endophyte-infested fescue were evident at hypothermal-am
bient temperatures. Deleterious effects of consumption of endophyte-in
fested fescue did not negatively affect subsequent feedlot performance
.