|FOOTE, ANDREW - University Of Kentucky|
|BUSSARD, JESSICA - University Of Kentucky|
|GOFF, BEN - University Of Kentucky|
|HARMON, DAVID - University Of Kentucky|
Submitted to: Kentucky Beef Report
Publication Type: Experiment Station
Publication Acceptance Date: 9/1/2012
Publication Date: 1/1/2014
Citation: Klotz, J.L., Aiken, G.E., Foote, A.P., Bussard, J.R., Brown, K.R., Goff, B.M., Harmon, D.L., Strickland, J.R. 2014. Vascular activity increases with time off of tall fescue. Kentucky Beef Report. pgs. 19-22.
Interpretive Summary: The objective of this experiment was to determine if the contractile response of lateral saphenous veins to ergot alkaloids and agonists for serotonin2A, '2A-, and '2C-adrenergic receptors changes as the time off of endophyte-infected tall fescue increases. The results of this study demonstrate that significant changes in peripheral vasoactivity occur beyond one month after cessation of ergot alkaloid exposure. These changes occur well beyond the time interval necessary for prolactin levels to increase (low concentrations are frequently used as an indication of fescue toxicosis) to normal levels. This would suggest that cattle might still be recovering from fescue toxicosis when they would be diagnosed otherwise if prolactin were used as the lone indicator of recovery.
Technical Abstract: Cattle continue to recover from depressed vasoactivity (vasoconstriction) beyond 60 days after removal from endophyte-infected tall fescue pasture and after prolactin (an indicator of fescue toxicosis) had returned to physiologic levels. This was determined by evaluating the contractile responses of lateral saphenous veins biopsied from cattle at different time points relative to their removal from a tall fescue pasture across 2 years. It was evident that no peripheral vascular recovery occurred within the first 28 days, but thereafter (days 42 and 63) increases in contractile response to different agonists were observed. These findings indicate that for a complete recovery from fescue toxicosis, animals should be removed from tall fescue pastures and fed a non-toxic diet for at least 6 weeks.