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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2008-1258v1 87/3/1184    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Looper, M. L. Articles by Rosenkrans, C. F. Search for Related Content PubMed PubMed Citation Articles by Looper, M. L. Articles by Rosenkrans, C. F., Jr.

Influence of toxic endophyte-infected fescue on sperm characteristics and endocrine factors of yearling Brahman-influenced bulls^1,2

M. L. Looper^*,3, R. W. Rorie, C. N. Person, T. D. Lester, D. M. Hallford, G. E. Aiken, C. A. Roberts^#, G. E. Rottinghaus^|| and C. F. Rosenkrans, Jr.

^* USDA-ARS, Dale Bumpers Small Farms Research Center, Booneville, AR 72927; and Department of Animal Science, University of Arkansas, Fayetteville, 72701; and Department of Animal and Range Sciences, New Mexico State University, Las Cruces 88003; and and USDA-ARS, Forage-Animal Production Research Unit, Lexington, KY 40546; and ^# Division of Plant Sciences, and ^|| Veterinary Medical Diagnostic Laboratory, University of Missouri, Columbia 65211.

³ Corresponding author: mike.looper{at}ars.usda.gov

Sixteen (mean age = 1.1 ± 0.1 yr; mean BW = 478 ± 34 kg) Brahman-influenced bulls were used to determine the influence of fescue type on sperm characteristics and serum concentrations of prolactin, cortisol, and testosterone. Bulls were blocked by BW, scrotal circumference (SC), and pregrazing sperm characteristics and randomly assigned to graze toxic endophyte-infected (EI; 4 bulls/pasture; 2 pastures) or novel endophyte-infected (NE; 4 bulls/pasture; 2 pastures) tall fescue for 121 d. Semen was collected by electroejaculation, and SC was measured and blood samples collected monthly. Sperm were evaluated for motility and morphology with an integrated visual optical system. Overall mean concentration of prolactin was decreased more (P < 0.01) in EI bulls than NE bulls from May to August. Scrotal circumference was not affected by fescue type (P = 0.58); overall SC averaged 36.7 ± 2.3 cm. Percentage of live sperm was not different (P = 0.24) between NE bulls (80%) than EI bulls (67%) in July and August. Bulls grazing NE fescue had more (P < 0.06) motile sperm than EI bulls in July and August. Percentages of progressive (57 vs. 38%, NE and EI, respectively; P < 0.06) and rapid (67 vs. 46%, NE and EI, respectively; P = 0.04) sperm were greater from bulls grazing NE than EI bulls in July and August. Average velocity of the smoothed sperm path and progressive velocity in a straight line from the beginning to the end of the sperm track were slower (P < 0.09) in EI bulls than NE bulls and were slower (P = 0.04) in August compared with July. Mean width of head oscillation as the sperm swims was less (P < 0.06) in August than July. Concentrations of cortisol and testosterone were not (P > 0.10) influenced by fescue type. Semen from bulls grazing EI had reduced motility and morphology than bulls grazing NE. Detrimental effects of toxic fescue may not be mediated by cortisol, testosterone, or both. Semen quality of bulls grazing toxic EI tall fescue was decreased with increased maximum ambient temperatures.

Key Words: bull • fescue • integrated visual optical system • sperm