Date Available

7-19-2021

Year of Publication

2021

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College

Agriculture, Food and Environment

Department/School/Program

Animal and Food Sciences

Advisor

Dr. David Harmon

Abstract

Cattle consuming endophyte-infected tall fescue (E+) typically experience a syndrome termed fescue toxicosis which is thought to be caused by ergot alkaloids produced by the endophyte. The most abundant alkaloid, and considered the most likely cause of the syndrome, is ergovaline (ERV). During fescue toxicosis, a decrease in ADG is observed which is likely due to the decrease in DMI commonly observed in animals consuming E+ compared to animals consuming non-endophyte-infected tall fescue (E-). However, the cause of the decrease in intake is not well elucidated. Many physiological responses control feed intake including, but not limited to, physical, neural, metabolic, and hormonal factors. The present study focused on investigating the impact of E+ consumption on hormonal factors related to intake regulation as well as investigating the effects on nonesterified fatty acid (NEFA) and b-hydroxybutyrate (BHB). Twelve growing Holsteins steers were assigned to one of three treatments (n=4 per treatment): 0 ppm ERV, 1.8 ppm ERV, and 2.7 ppm ERV. Animals were adapted to the treatment diets for 7 days followed by a 7-day treatment period.Cattle were catheterized to facilitate blood sampling. Blood samples (25mL) were collected every 20 minutes for 8 hours, beginning 1-hour before feeding, on day 7 of the treatment period. Samples were centrifuged for 30 minutes at 5000 x g at 4 C, and plasma was aliquoted for hormone, NEFA, and BHB analysis. DMI intake decreased linearly (p< 0.0001) with increasing intake of ERV. Plasma insulin and leptin concentrations both displayed a quadratic response. Plasma active ghrelin exhibited a linear response (p=0.0431) where concentrations decreased as ERV concentration increased. NEFA concentrations produced a significant treatment x time interaction (p< 0.0001). BHB concentrations exhibited a quadratic response where concentrations were lowest for the 2.7 ppm ERV treatment (p=0.0286). Glucose concentrations were shown to increase linearly with increasing ERV intake (p=0.0456). These results indicate that consumption of E+ decreases intake which may be possible through alteration of hormones related to intake regulation and potentially alter postabsorptive metabolism.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2021.258

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