Growth and subsequent feedlot performance of estradiol-implanted vs nonimplanted steers grazing fall-accumulated endophyte-infested or low-endophyte tall fescue.
1995
Beconi M.G. | Howard M.D. | Forbes T.D.A. | Muntifering R.B. | Bradley N.W. | Ford M.J.
A growing-finishing study using Angus steer calves was conducted in three phases: 1) grazing stockpiled 'Kentucky-31' tall fescue (Festuca arundinacea Schreb.) with high (65%; HE KY-31) and low (0%; LE KY-31) infestation rates of Acremonium coenophialum Morgan-Jones and Gams and 'Kenhy' and 'Johnstone' tall fescue with low (< 1%) infestation rate of Acremonium coenophialum from October 24 to December 19; 2) drylot feeding 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 August 1). In Phase 1, ADG was greatest (P < 0.05) for Kenhy, intermediate for Johnstone and LE KY-31, and lowest (P < 0.06) for HE KY-31. Implantation with estradiol 17-beta increased ADG (P < 0.01) by 23, 27, 7, and 2% for steers grazing Johnstone, HE KY-31, LE KY-31, and Kenhy, respectively. Dry matter digestibility and DMI of stockpiled Johnstone and HE KY-31 were not different (P > 0.10). During Phase 2, steers consuming Johnstone haylage had greater (P < 0.01) DMI, ADG, and gain:feed ratio (G:F) than steers consuming HE KY-3 1 haylage. During Phase 3, steers previously consuming Johnstone had greater DMI (P < 0.10); however, steers previously fed HE KY-31 had greater ADG (P < 0.05) and G:F (P < 0.01). By the end of the study, steer body weights were not different (P > 0.10) between treatments. These data indicate that growth-decreasing effects of endophyte-infested fescue were evident at hypothermal-ambient temperatures. Deleterious effects of consumption of endophyte-infested fescue did not negatively affect subsequent feedlot performance.
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