1st Page



This article in JAS

  1. Vol. 91 No. 8, p. 3686-3692
    unlockOPEN ACCESS
    Received: Nov 7, 2012
    Accepted: May 3, 2013
    Published: November 25, 2014

    2 Corresponding author(s):


Effects of fescue toxicosis on bull growth, semen characteristics, and breeding soundness evaluation1

  1. H. M. Stowe*,
  2. M. Miller*,
  3. M. G. Burns*,
  4. S. M. Calcatera*,
  5. J. G. Andrae*,
  6. G.E. Aiken,
  7. F. N. Schrick,
  8. T. Cushing§,
  9. W. C. Bridges* and
  10. S. L. Pratt 2
  1. Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC 29634
    USDA-ARS-Forage-Animal Production Research Unit, University of Kentucky Campus, Lexington 40546
    Department of Animal Science, University of Tennessee, Knoxville 37996
    Livestock and Poultry Health, Clemson University, Columbia, SC 29229


Tall fescue possesses heat, drought, and pest resistance conferred to the plant by its mutualistic relationship with the ergot alkaloid producing fungal endophyte, Neotyphodium coenophialum. The objective of this study was to evaluate the impact of ergot alkaloid consumption on growth, scrotal circumference (SC), and semen quality. The SC measurement and percentage of motile and normal sperm were used to determine if a bull passed the breeding soundness exam (BSE) requirements. Bulls (n = 14) between 13 and 16 mo of age exhibiting ≥32 cm SC and having passed a BSE were assigned to 1 of 2 dietary treatments accounting for BCS and BW. Bulls were fed the treatment diet containing toxic tall fescue seed (E+; 0.8 μg of ergovaline and ergovalanine/g DM) or the control diet containing endophyte-free nontoxic tall fescue seed (E–) for 126 d. Blood samples were collected and BSE and BCS accessed at the start of the test (d 0) and every 21 d to the end of test (d 126). Weights were obtained on d 0 and d 126. Serum prolactin (PRL) concentrations were affected by treatment × day interactions (P = 0.04) verifying the effectiveness of the E+ diet. Bulls consuming the E+ diet exhibited declining PRL concentrations from 250 ± 52.1 ng/mL on d 0 to 30.6 ± 46.9 ng/mL by d 126 whereas bulls receiving the E– ration maintained serum PRL concentrations greater than or equal to 226.7 ± 50.4 ng/mL across the 126-d study. Body condition score (P = 0.4) and BW (P = 0.4) were not different between treatments. No difference due to treatment was observed for the percentage of bulls passing a standard BSE exam (P = 0.6) and no treatment effect was observed for any semen characteristic measured by computer-assisted semen analysis (CASA; P ≥ 0.2). The SC was negatively affected by treatment × day interaction (P = 0.04) with E– bulls exhibiting a larger SC at d 126 compared with E+ bulls of 36.7 ± 0.8 versus 34.3 ± 0.8 cm, respectively. Within treatment, E+ bulls exhibited a decrease in SC (P = 0.0001) with a d 0 SC of 37.3 ± 0.8 cm and dropping to 34.3 ± 0.8 by d 126. Theoretically, reduced SC would negatively impact semen quality, but this was not observed. However, CASA and BSE evaluation data are consistent with recent reports indicating that bulls grazing E+ tall fescue exhibited only subtle, if any, differences on semen characteristics.

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