HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) All Versions of this Article: jas.2008-1562v1 87/6/2142    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 Aiken, G. E. Articles by Schrick, F. N. Search for Related Content PubMed PubMed Citation Articles by Aiken, G. E. Articles by Schrick, F. N.

Hemodynamics are altered in the caudal artery of beef heifers fed different ergot alkaloid concentrations

G. E. Aiken^*, J. R. Strickland^*, M. L. Looper, L. P. Bush and F. N. Schrick

^* USDA-ARS, Forage-Animal Production Research Unit, Lexington, KY 40546 , USDA-ARS, Dale Bumpers Small Farms Research Center, Booneville, AR 72927 , University of Kentucky, Lexington, KY 40546 University of Tennessee, Knoxville, TN 37996-4574

glen.aiken{at}ars.usda.gov

Abstract

Doppler ultrasonography was used to compare blood flow characteristics in the caudal artery of heifers fed diets with either endophyte (Neotyphodium coenophialum) non-infected (E-, 0 µg of ergovaline/g of DM), a 1:1 mixture of endophyte-infected and E- (E+E-; 0.39 µg of ergovaline/g of DM), or endophyte-infected (E+, 0.79 µg of ergovaline/g of DM) tall fescue (Lolium arundinaceum) seed. Eighteen crossbred (Angus x Brangus) heifers [345 ± 19 kg (SD)] were assigned to individual pens and fed chopped alfalfa hay plus a concentrate that contained E- tall fescue seed for 7 d during an adjustment period. A 9-d experimental period followed with feeding treatments of chopped alfalfa hay plus a concentrate with either E+, E-, E+E- seed being assigned randomly to pens. Doppler ultrasound measurements (caudal artery luminal area, peak systolic velocity, end diastolic velocity, mean velocity, heart rate, and flow rate) and serum prolactin were monitored during the adjustment (3 baseline measures) and during the experimental period (7 measures). Statistical analyses compared proportionate differences between baseline and responses at 3, 27, 51, 75, 171, and 195 h from initial feeding of the experimental diets. Serum prolactin concentrations for E+ and E+E- diets were lower (P < 0.001) than baseline concentrations beginning at 27 and 51h, respectively, from initial feeding of the diets. Although baseline measures were taken when ambient temperatures were likely below thermoneutrality, caudal artery luminal cross-sectional area in E+ heifers had declined (P = 0.004) from baseline by 27 h and remained lower (P < 0.02) until 195 h, and caudal artery luminal area declined (P = 0.004) in E+E- heifers from baseline by 51 h and remained lower (P < 0.07) until 171 h. Blood flow rate was slower than the baseline rate at 51 h for E+ (P = 0.058) and E+E- (P = 0.02 heifers, but blood flow remained slower in E+E- heifers at 48 h, whereas it remained slower in E+ heifers for 96 h. Adjustments in artery luminal area and blood rate with the 3 diets appeared to parallel the increases in ambient temperature. Heifers fed a diet containing a larger amount of ergot alkaloids had less of a response to ambient temperature than heifers consuming the diet with lower or no ergot alkaloids.

Key Words: Beef cattle • Doppler ultrasonography • fescue toxicosis • Lolium arundinaceum • tall fescue • vasoconstriction