|BURNS, M - Clemson University|
|STOWE, H - Clemson University|
|ANDRAE, J - Clemson University|
|PRATT, S - Clemson University|
Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2015
Publication Date: 4/1/2015
Citation: Aiken, G.E., Burns, M.G., Stowe, H.M., Andrae, J.G., Pratt, S.L. 2015. Vasoconstrictive responses of the testicular and caudal arteries in bulls exposed to ergot alkaloids from tall fescue. Professional Animal Scientist. 31:130-136. doi:10.15232\pas.2014-01373.
Interpretive Summary: Tall fescue [Lolium arundinaceum (Schreb.) Darbysh] is the predominant grass utilized for pasture in the transition zone between the temperate northeast and subtropical southeast; however, ergot alkaloids produced by an endophyte (Neotyphodium coenophialum) that infects most tall fescue plants can cause a toxicosis in cattle that reduces growth and thriftiness, and reproductive performance. The alkaloids cause some hormonal imbalance and induce a persistent constriction of the vasculature that reduces the animal’s ability to regulate core body temperatures. Reduced calving percentages and weaning weights have been estimated to cost the U.S. beef industry over 1 billion dollars annually. Although most of the research on effects of ergot alkaloids on cattle reproduction has focused on heifers and cows, recent research has evaluated ergot alkaloid effects on bull fertility. A collaboration between USDA-ARS Forage-Animal Production Research Unit and the Department of Animal and Veterinary Sciences at Clemson University used color Doppler ultrasonography to determine a vasoconstrictive response by the testicular arteries in bulls that consumed endophyte-infected tall fescue seed in a pen experiment and also in bulls that grazed endophyte-infected tall fescue pastures. Blood flow constriction was coupled with subtle negative effects on some fertility traits in the bulls on toxic treatments. The research indicated that ergot alkaloid induced vasoconstriction could decrease blood flow to the testes and make it a contributing factor in reducing conception rates for cow herds grazing endophyte-infected tall fescue.
Technical Abstract: Color Doppler ultasonography was used to evaluate vasoconstrictive responses of the testicular artery in yearling bulls to ergot alkaloids. Ergot alkaloid-induced constriction of the testicular artery could disrupt thermoregulation of the testes and reduce bull fertility. Luminal areas of the testicular artery were monitored during two experiments that evaluated fertility traits and sperm characteristics of bulls. Experiment 1 (pen experiment) compared diets containing toxic endophyte-infected or endophyte-free tall fescue seed, and experiment 2 (grazing experiment) compared grazing diets consisting of toxic endophyte-infected and non-toxic endophyte-infected tall fescue pasture. Ultrasound images were acquired on three dates during the 126-d pen experiment and on four dates during the 155-d grazing experiment. Luminal area of the caudal artery also was monitored as an indicator of alkaloid-induced constriction of blood flow to peripheral tissues. Caudal and testicular arteries in bulls on the toxic endophyte treatment responded similarly in each experiment. Across imaging dates for the pen experiment, caudal artery lumens in bulls fed the toxic diet averaged 42% less (P < 0.01) luminal area than those fed the nontoxic diet, and testicular arteries in bulls fed the toxic diet averaged 40% less (P < 0.05) area than those fed the nontoxic diet. For the grazing experiment, there were interactions (P < 0.05) between treatment and imaging date on caudal and testicular artery luminal areas. Differences between treatments were not detected until the last two image dates, with luminal areas of caudal and testicular arteries on the last imaging date for the toxic tall fescue being 46 and 41%, respectively, less than for the nontoxic fescue grazing treatment. Results indicated that ergot alkaloids in toxic endophyte-infected tall fescue can induce constriction of blood flow to the testes that could potentially adversely affect bull fertility.