Session: SSASAS: Small Ruminant Production I

470 - Changes in Cytochrome P450 in Katahdin Ewes Fed Endophyte-infected Tall Fescue Seed Diets in Spring and Fall

Friday, July 16, 2021

4:45 PM – 5:00 PM EST

Location: Kentucky International Convention Center (KICC), L006

Presenting Author(s)

Mohan Acharya

Post Doc
Department of Animal Science, University of Arkansas
Fayetteville, Arkansas

PDF Slides and Audio

Author(s)

Joan M. Burke, PhD

Research Animal Scientist
USDA-ARS
Booneville, Arkansas
EW

Erin Wood

USDA-ARS
Booneville, Arkansas
Yan Huang, PhD

Assistant Professor
University of Arkansas
Fayetteville, Arkansas
PM

Palika Dias Morse

Department of Animal Science, University of Arkansas
Fayetteville, Arkansas
KC

Ken Coffey

University of Arkansas
Fayetteville, Arkansas
EL

Edwards J L. Lannett

Department of Animal Science, University of Tennessee
Knoxville, Tennessee
CR

Charles F Rosenkrans, Jr.

Department Chair and Professor
Animal and Veterinary Sciences Department, Clemson University
Clemson, South Carolina

Objective was to examine the activity of cytochrome P450 (CYP), a liver enzyme that metabolizes ergot alkaloids which is hindered by this fescue toxin, as an indicator of fescue toxicosis in sheep. In spring and fall, ewes were blocked by age and BW, and randomly assigned to 1 kg/ewe/d of endophyte-infected (E+; 61% of diet in fall, 13% of diet in spring; 0.8 µg/g of ergovaline; and soy hulls, alfalfa pellets, cottonseed hulls, molasses) or non-infected (E-; same proportion of E+/season and same feeds) tall fescue seed supplement (n = 10/diet in each season) for 28 d, plus hay, mineral and water. Ewes were exposed to teaser, d -21 to 0, and intact rams, d 0 (first day of diet) to 30. Rectal temperature (RT), serum concentration of prolactin (using RIA), and CYP were determined every 7–14 d between d 0–28, and pregnancy status on d 56. Promega^TMP450-Glo assay was used to determine CYP from serum. Data were analyzed by using PROC MIXED with repeated measures (SAS). Rectal temperature of E+ compared with E- ewes was elevated on at least one day in fall and spring (diet × season × d, P < 0.001). Serum prolactin was lower in E+ compared with E- ewes (diet × d, P < 0.001) and lower in fall (P < 0.001). CYP was higher in E- ewes on d 28 in fall (diet × season × d, P = 0.008), but otherwise similar between diets, and higher in fall than spring (P < 0.001). There was an unexpected negative correlation between CYP and prolactin (R = -0.24; P < 0.009), but there appears to be a subpopulation of ewes with low prolactin and lower CYP. CYP activity in sera may not be a marker for fescue toxicosis in ewes.