Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Dinh, Thu

Committee Member

Blanton, John

Committee Member

Baldwin, Brian

Committee Member

Martin, Steve

Committee Member

Schilling, Wes

Date of Degree

5-3-2019

Document Type

Dissertation - Open Access

Major

Animal and Dairy Sciences

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Agriculture and Life Sciences

Department

Department of Animal and Dairy Sciences

Abstract

The objective of this study was to determine the effects of feeding endophyte-infected tall fescue seed to Angus steers on average daily gain, carcass characteristics, ergovaline concentration, lipid oxidation, hepatic enzyme activity, metmyoglobin reductase activity, and mitochondrial lipid composition. Animals were blocked into light, medium, and heavy body weight groups and were randomly assigned to either a KY31 seed treatment (6796 ppb ergovaline; 20 MUg/kg BW; E+; n = 6) or a KY32 control (< 100 ppb; E-; n = 6). There was a 2-way treatment × time interaction effect on ADG (P < 0.001). The E+ steers gained 0.56 kg/d less than the E- steers from d 0 to 14 (P < 0.001) until d 56 (ADG difference = 0.27 kg/d; P = 0.007) but both group had similar ADG from d 70 till the end of the feeding period 2 (ADG = 0.53 kg/d; P > 0.070). No difference in carcass characteristics were found between the E+ and E- steers by at the time of ultrasonography (P >= 0.120) or at harvest (P >= 0.199). In both period 1 and 2, there was a 2-way treatment × time interaction for ergovaline concentration in blood (P = 0.002 and 0.022, respectively). Infected tall fescue seed did not change d-3 hepatic enzyme activity in both feeding periods (P = 0.149 to 0.645). In period 1, thiobarbituric acid reactive substances, primarily consisting of malondialdehyde (MDA), were greater in blood serum of E+ steers than E- steers (6.56 MUM vs. 2.56 MUM; P = 0.048). An overall increase in MDA from d 0 (2.39 MUM) to d 3 (7.59 MUM) was also observed (P = 0.049). There was no effect of endophyte infected tall fescue seed on metmyoglobin reductase in longissimus thoracis (4.82 MUM/min/g in E- muscle vs. 3.93 MUM/min/g in E+ muscle; P = 0.484. There was no treatment effect on mitochondrial lipid composition (P >= 0.094), including phospholipids and fatty acids.

URI

https://hdl.handle.net/11668/21082

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