Arterial Responses to Acute Low-Level Ergot Exposure in Hereford Cows

Abstract

Ergot alkaloids are toxic secondary metabolites produced by the fungus Claviceps purpurea that contaminate cereal grains. Current Canadian standards allow 2 to 3 parts per million of ergot alkaloids in animal feed. The purpose of this study was to determine whether hemodynamic parameters were altered when beef cows were fed permissible levels of ergot alkaloids (i.e., <3 ppm) on a short-term basis. A dose-response relationship between ergot alkaloid concentration and hemodynamic changes in caudal (coccygeal), median sacral, and internal iliac arteries was hypothesized. Beef cows were randomly allocated to: Control (<15 μg total ergot alkaloids/kg dry matter), Low (132 μg/kg), Medium (529 μg/kg), and High (2115 μg/kg) groups (n = 4 per group). Animals were fed 8.8 kg of dry matter daily for 4 days (pre-treatment), 7 days (treatment), and 4 days (post-treatment). The caudal, median sacral, and internal iliac arteries were examined daily using ultrasonography in B-mode and Doppler (color and spectral) mode and hemodynamics endpoints were analyzed by repeated measures mixed model analyses. Caudal artery diameter decreased in the Medium (p = 0.004) and High (p < 0.001) groups compared to pre-treatment values and the pulsatility index increased (p ≤ 0.033) in all ergot treatments during the post-exposure period compared to the Control group. Blood volume per pulse (mL) and blood flow (mL/min) through the caudal artery during the treatment period were reduced in the Medium (−1.0 mL reduction; p ≤ 0.004) and High (−1.1 mL p ≤ 0.006) groups compared to pre-treatment values. The median sacral artery diameter decreased in the Medium (p = 0.006) and High (p = 0.017) treatments compared to the Control group. No differences were detected in any hemodynamic endpoints for the internal iliac artery except changes in pulse rate (p = 0.011). There was no treatment (p > 0.554) or Treatment*Time interaction (p > 0.471) for plasma prolactin concentration or body temperature. In conclusion, alterations in caudal artery hemodynamics were detected when cows were fed 529 and 2115 μg ergot alkaloids per kg dry matter per day for 1 week. The caudal artery was more sensitive to ergot alkaloids than the median sacral and internal iliac arteries. Our results partially support the hypothesis of a dose-response effect of ergot alkaloids in feed on hemodynamics.

Arterial Responses in Periparturient Beef Cows Following a 9-Week Exposure to Ergot (Claviceps purpurea) in Feed

“…Total concentrations of ergot alkaloids in feed in this study were designed to be within current Canadian guidelines for cattle, corresponding to 2,000–3,000 μg/kg total mixed ration (3). Based on the results of a previous study (20), concentrations were chosen to be conservative of development of vascular alterations as cattle were to be fed for a longer period of time than that study.…”

“…The caudal artery and right branch of the internal iliac artery were evaluated weekly using ultrasonography as described previously (20). The caudal artery was chosen based on its previously documented sensitivity to ergot alkaloids in feed (20, 22, 23).…”

“…The caudal artery and right branch of the internal iliac artery were evaluated weekly using ultrasonography as described previously (20). The caudal artery was chosen based on its previously documented sensitivity to ergot alkaloids in feed (20, 22, 23). The internal iliac artery was selected to serve as a negative control based on the results of a previous study in which no hemodynamic changes, aside from altered pulse rate, were observed in the internal iliac following 1-week exposure to ergot alkaloids in feed in beef cows (20).…”

“…The caudal artery was chosen based on its previously documented sensitivity to ergot alkaloids in feed (20, 22, 23). The internal iliac artery was selected to serve as a negative control based on the results of a previous study in which no hemodynamic changes, aside from altered pulse rate, were observed in the internal iliac following 1-week exposure to ergot alkaloids in feed in beef cows (20). Briefly, the caudal artery was imaged at the fourth coccygeal vertebra, while the internal iliac artery was measured between the uterine and vaginal branches.…”

“…In a previous study by our research group, beef cows were fed C. purpurea ergot alkaloids for 1 week and observed for signs of vasoconstriction in the caudal artery at 529 and 2,115 μg total ergot alkaloids (ergocristine, ergocornine, ergocryptine, ergosine, ergotamine, and ergometrine) per kg of dry matter (20). The caudal artery of these animals recovered to pre-treatment status once ergot was removed from the feed.…”