title: Ergot alkaloids from endophyte-infected tall fescue decrease reticuloruminal epithelial blood flow and volatile fatty acid absorption from the washed reticulorumen.
abstract: An experiment was conducted to determine if ergot alkaloids affect blood flow to the absorptive surface of the rumen. Steers (n=8) were pair-fed alfalfa cubes and received ground endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum; E+) seed (0.015 mg ergovaline·kg BW(-1)·d(-1)) or endophyte-free tall fescue (E-) seed via the rumen cannula 2x daily for 7 d at thermoneutral (TN; 22°C) and heat stress (HS; 32°C) conditions. On d 8, the rumen was emptied and rinsed. A buffer containing VFA was incubated in the following sequence: control (CON), 15 μg ergovaline·kg BW(-1) (1×EXT) from a tall fescue seed extract, and 45 μg ergovaline·kg BW(-1) (3×EXT). For each buffer treatment there were two 30-min incubations: a 30-min incubation of a treatment buffer with no sampling followed by an incubation of an identical sampling buffer with the addition of Cr-EDTA and deuterium oxide (D2O). Epithelial blood flow was calculated as ruminal clearance of D2O corrected for influx of physiological water and liquid outflow. Feed intake decreased with dosing E+ seed at HS but not at thermoneutral conditions (TN; P<0.02). Dosing E+ seed decreased serum prolactin (P<0.005) at TN. At HS, prolactin decreased in both groups over the 8-d experiment (P<0.0001), but there was no difference in E+ and E- steers (P=0.33). There was a seed treatment×buffer treatment interaction at TN (P=0.038), indicating that E+ seed treatment decreased reticuloruminal epithelial blood flow at TN during the CON incubation, but the two groups of steers were not different during 1×EXT and 3×EXT (P>0.05). Inclusion of the extract in the buffer caused at least a 50% reduction in epithelial blood flow at TN (P=0.004), but there was no difference between 1×EXT and 3×EXT. There was a seed × buffer treatment interaction at HS (P=0.005), indicating that the reduction of blood flow induced by incubating the extract was larger for steers receiving E- seed than E+ seed. Volatile fatty acid flux was reduced during the 1×EXT and 3×EXT treatments (P<0.01). An additional experiment was conducted to determine the effect of time on blood flow and VFA flux because buffer sequence could not be randomized. Time either increased (P=0.05) or did not affect blood flow (P=0.18) or VFA flux (P>0.80), indicating that observed differences are due to the presence of ergot alkaloids in the rumen. A decrease in VFA absorption could contribute to the signs of fescue toxicosis including depressed growth and performance.
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington 40546-0215.
authors.forename: A P
authors.initials: AP
authors.lastname: Foote
authors.forename: N B
authors.initials: NB
authors.lastname: Kristensen
authors.forename: J L
authors.initials: JL
authors.lastname: Klotz
authors.forename: D H
authors.initials: DH
authors.lastname: Kim
authors.forename: A F
authors.initials: AF
authors.lastname: Koontz
authors.forename: K R
authors.initials: KR
authors.lastname: McLeod
authors.forename: L P
authors.initials: LP
authors.lastname: Bush
authors.forename: F N
authors.initials: FN
authors.lastname: Schrick
authors.forename: D L
authors.initials: DL
authors.lastname: Harmon
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects / Q000662:veterinary*; D002417:Cattle; D004032:Diet / Q000662:veterinary; D060026:Endophytes / Q000502:physiology*; D004876:Ergot Alkaloids / Q000633:toxicity*; D005232:Fatty Acids, Volatile / Q000378:metabolism; D006358:Hot Temperature; D008297:Male; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D006109:Poaceae / Q000382:microbiology*; D011388:Prolactin / Q000097:blood; D012159:Reticulum / Q000098:blood supply* / Q000378:metabolism; D012417:Rumen / Q000098:blood supply*; D012639:Seeds / Q000737:chemistry
chemical_list: D004876:Ergot Alkaloids; D005232:Fatty Acids, Volatile; D010936:Plant Extracts; D011388:Prolactin