Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2012
Publication Date: 7/15/2012
Citation: Foote, A.P., Kristensen, N.B., Klotz, J.L., Kim, D.H., Koontz, A.F., Mcleod, K.R., Bush, L.P., Harmon, D.L. 2012. Ergot alkaloids decrease rumen epithelial blood flow. J. Anim. Sci. Vol. 90, Suppl. 3:431-432. Interpretive Summary:
Technical Abstract: Two experiments were conducted to determine if ergot alkaloids affect blood flow to the absorptive surface of the rumen of steers. Steers (n=8 total) were pair-fed alfalfa cubes at 1.5× NEM and received ground endophyte-infected tall fescue seed (E+) or endophyte-free tall fescue seed (E-) via rumen cannula 2× daily for 7 d followed by ruminal incubation of a fescue seed extract at thermoneutral (TN; 21 °C) and heat stress (HS; 32°C) conditions. On d 8 rumen contents were removed and the rumen was emptied and rinsed. Buffer (bicarbonate-based buffer with VFA) was incubated in the following sequence for Exp 1: control (CON), 0.015 mg ergovaline/kg BW (1×EXT), and 0.045 mg ergovaline/kg BW (3×EXT). Ergovaline was supplied as an extract of tall fescue seed. Because we could not randomize the treatment sequence in Exp 1, in Exp 2, CON buffer was incubated 3 times to compare the changes occurring in epithelial blood flow over time of incubation. For each buffer there were 2 30-min incubations. There was a 30 min incubation of a treatment buffer with no sampling followed by removal of the buffer and incubation of an identical sampling buffer with the addition of Cr-EDTA and deuterium oxide (D2O). Epithelial blood flow was estimated as ruminal clearance of D2O that was corrected for influx of physiological water and liquid outflow. Feed intake decreased with dosing E+ at HS but not at TN (temp*day; P=0.016). In Exp 1, seed treatment did not affect rumen epithelial blood flow (P=0.73). Inclusion of the seed extract in the buffer caused approximately a 50% reduction in epithelial blood flow (P<0.0001) but there was no difference between the 1× and 3× treatments (P=0.53). 3× EXT tended to reduce blood flow more at TN than HS (P=0.11). In Exp 2 E+ steers had approximately a 20% reduction in blood flow between the first and second incubation of CON (P=0.005) but blood flow only tended to differ between CON incubation 1 and 3 (P=0.053). E- steers had (40%) greater blood flow during the third CON incubation (P=0.001). Chronic exposure to ergot alkaloids through dosing steers with TF seed did not alter rumen epithelial blood flow; however, acute exposure through inclusion of ergot alkaloids in the washed rumen buffer did decrease rumen epithelial blood flow indicating that gut vasculature does respond to acute alkaloid exposure.