Submitted to: International Symposium on Fungal Endophytes of Grasses
Publication Type: Abstract Only
Publication Acceptance Date: November 3, 2006
Publication Date: March 25, 2007
Citation: Aiken, G.E., Kirch, B.H., Strickland, J.R. 2007. Dyanmics of Peripheral Bloodflow for Endophyte-Naive Cattle Fed Toxic Tall Fescue Seed. Proceedings of the 6th International Symposium on Fungal Endophytes of Grasses. Grassland Research and Practice Series. 13:387-389. Technical Abstract: Blood flow in cattle grazed on toxic tall fescue is constricted to peripheral tissues because certain ergot alkaloids produced by the Neotyphodium endophyte that inhabits most tall fescue plants bind alpha-adrenergic receptors in the vasculature of cattle. Although the adverse effects that ergot alkaloids have on vascular circulation are understood, sensitivity of the bovine vascular system to ergot alkaloids has not been fully elucidated. Doppler ultrasonography was used to study blood flow through the caudal artery of heifers fed either toxic or non-toxic seed. Eighteen heifers that had never been exposed to tall fescue were stratified by weight for assignment to pens (3 heifers/pen) and toxic and non-toxic seed treatments were assigned to 6 pens in a completely randomized design (3 reps). Chopped alfalfa hay was fed ad libitum to each pen for 7 d, chopped alfalfa plus concentrate containing nontoxic seed for the next 7 d, and the alfalfa-concentrate toxic seed mixture was fed to assigned pens for the following 11 d. The alfalfa-concentrate ration with toxic seed contained 0.8 ppm ergovaline. Ultrasound images were collected at -92, -60, 4, 28, 52, 76, 100, 172, 268 hours from the initial feeding of the toxic diet (heifers were fed daily at 0900 h and scanned starting at 1300 h). Caudal artery area for heifers on the toxic diet were less (P < 0.01) than for those on the non-toxic diet at 0.17 d (toxic = 3.7 mm2, non-toxic = 5.0 mm2) and the difference increased and stabilized by 1.17 d (toxic = 2.0 mm2, non-toxic = 5.1 mm2). Following placement on the toxic diet, there was a tendency (P < 0.10) for lower heart rates with the toxic diet (toxic = 94 beats/min., non-toxic = 113 beats/min.). Before placement on the toxic diets, blood flow rates averaged 49.6 ml3/sec and declined to a mean flow of 25.2 ml3/sec. Results indicated a rapid change in vascular circulation following initial consumption of ergot alkaloids.