Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Animal Science

Major Professor

John T. Mulliniks

Committee Members

Janice L. Edwards, Brian Whitlock, Justin Rhinehart


Livestock grazing endophyte-infected tall fescue can have decreased performance due to vasoconstriction and reduced reproductive performance. Therefore, the objective of this study was to determine the effect of supplementing rumen-protected arginine to cows consuming endophyte-infected tall fescue seed on caudal blood flow and LH dynamics. Four ruminally cannulated, open beef cows (539 ± 30 kg) were used in a 2 x 2 factorial arrangement of treatments utilizing a Latin Square design with 4 periods of 31 d each. Each cow was assigned to individual pens and fed orchardgrass hay (10.3% CP and 85% NDF; OM basis) during a 10-d adaptation period, followed by a 21-d collection period in which each cow was assigned one of 4 treatments: (1) rumen-protected ARG (180 mg/kg of BW) and 1.0 kg/d of endophyte-infected fescue seed (AE+); (2) rumen-protected ARG (180 mg/kg of BW) and 1.0 kg/d of non-infected fescue seed (AE-); (3) 1.0 kg/d of endophyte-infected fescue seed (E+) alone; or (4) 1.0 kg/d of non-infected fescue seed (E-) alone. In each period, doppler ultrasound measurements for blood flow parameters were quantified on d 1, 5, 10, 15, and 19. On d 20 of each period, blood samples were collected every 10 min for 6 h and then once every hour for 12 h. Caudal blood flow exhibited an interaction (P = 0.05) of ARG × fescue seed type, resulting from an increase in blood flow in cows fed rumen-protected ARG. In addition, mean velocity was greater (P = 0.01) with the inclusion of rumen-protected ARG in the diet. Caudal artery area (P = 0.03) and diameter (P = 0.01) were decreased in cows consuming E+ compared to E- with no effect (P ≥ 0.38) by ARG supplementation. Mean serum LH concentration exhibited (P = 0.02) an ARG × fescue seed type interaction. Cows consuming E+ had decreased LH concentrations compared to all other treatments. However, cows consuming AE+ had similar LH concentrations compared to cows consuming AE- or E-. Thus, supplementing rumen-protected ARG to cows grazing endophyte-infected fescue seed has the potential to increase reproductive performance and peripheral blood flow.

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