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Journal of Animal Science Abstract - Animal Nutrition

Effects of selected endophyte and tall fescue cultivar combinations on steer grazing performance, indicators of fescue toxicosis, feedlot performance, and carcass traits13


This article in JAS

  1. Vol. 91 No. 1, p. 342-355
    Received: Sept 19, 2011
    Accepted: Aug 23, 2012
    Published: December 3, 2014

    4 Corresponding author(s):

  1. J. A. Parish 4,
  2. J. R. Parish,
  3. T. F. Best*,
  4. H. T. Boland* and
  5. C. A. Young
  1. Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State 39762-9815
    Department of Plant and Soil Sciences, Mississippi State University, Mississippi State 39762-9555
    The Samuel Roberts Noble Foundation, Ardmore, OK 73401


Five tall fescue [Lolium arundinaceum (Schreb.)] pastures [wild-type ‘Kentucky-31’ with 78.0% of plants infected with ergot alkaloid-producing endophyte Neotyphodium coenophialum (KY31 E+), ‘Jesup’ AR542 endophyte-infected contaminated with 30.3% tall fescue containing ergot alkaloid producing-endophyte (Jesup AR542 E+); ‘GA-186’ AR584 endophyte-infected contaminated with 11.8% tall fescue containing ergot alkaloid producing-endophyte (AGRFA 140); ‘PDF’ AR584 endophyte-infected contaminated with 5.5% tall fescue containing ergot alkaloid producing-endophyte (AGRFA 144); and ‘KYFA 9301’ AR584 endophyte-infected contaminated with 10.0% tall fescue containing ergot alkaloid producing-endophyte (AGRFA 150)] were compared for steer growth performance, toxicity, feedlot performance, and carcass traits. Steers (mean initial BW = 322 kg) grazed pastures for 84 d in spring and 56 d in autumn for 2 yr. Steers were shipped after grazing in Prairie, MS, to Macedonia, IA, for finishing. Mean herbage mass was not different (P = 0.15) among pastures. Posttreatment (d 28+) serum prolactin concentrations were depressed (P = 0.013) on KY31 E+. Steers grazing KY31 E+ had greater (P < 0.01) posttreatment rectal temperatures during spring. Spring hair coat scores were greatest (P < 0.01) on KY31 E+ at d 56 and 84. Steer ADG was least (P < 0.01) on KY31 E+ in spring and depressed (P = 0.014) on KY31 E+ and Jesup AR542 E+ in autumn. Spring grazing ADG was greater (P = 0.049) on AGRFA 150 than Jesup AR542 E+ and AGRFA 140. No BW differences (P = 0.09) among pastures were seen at reimplant during feedlot finishing. Pasture had no effect on ADG after reimplant (P = 0.68), days on feed (P = 0.56), or final BW (P = 0.55). Exposure to fescue toxicosis did not affect (P ≥ 0.19) carcass traits. Hair coat price discounts applied for spring-grazed steers on KY-31 E+ affected (P < 0.01) initial steer monetary values. There were no pasture differences for finishing costs (P ≥ 0.61) or final carcass value (P = 0.59). Elite tall fescue cultivar and novel endophyte combinations improve growth performance of grazing calves over KY31 E+. Producers whose calves graze KY-31 E+ tall fescue should consider retaining ownership of these cattle through feedlot finishing to avoid market discounts and capture value from compensatory BW gains during finishing.

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