Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science


The effect of stress on intramuscular and plasma lipids was studied in rabbits and beef. Nine mature rabbits were subjected to a constant infusion of ACTH (1.5 mU./min./kg.). Four rabbits completed a 12 hour treatment and two completed an 11-hour treatment. The remaining three rabbits survived treatments of 6, 4, and 2 hours. Blood samples taken at 0, 1, 3, 6, 9 and 12 hours or immediately upon death if it occurred before 12 hours. Initial and final muscle biopsies were taken from the longissimus dorsi directly posterior to the 13th rib on right and left sides, respectively. The stress evoked by a 2-day marketing period was evaluated in 11 yearling fed steers. Following initial biopsy of the left longissimus dorsi steers were placed in an unfamiliar lot with feed and water for 42 hours after the initial biopsy. At the completion of this holding period, animals were trucked 120 kilometers to a commercial packing house where they were slaughtered 48 hours after the initial biopsy. Carcasses were chilled 48 hours before the final sample was removed from the right longissimus dorsi. Plasma and intramuscular lipids were extracted with chloroform-methanol and the resulting total lipid (TL) was separated into classes by thin-layer chromatography. Free fatty acids (FFA), triglycerides (TG), cholesterol (C) and cholesteryl esters (CE) were estimated quantitatively by photoreflectometric techniques which were developed in the course of this research. Micro determinations of phosphorus were utilized to measure phospholipids (PL). The purpose of this research was to determine if the source of such FFA [free fatty acids] might be the intramuscular lipid of the longissimus dorsi, commonly called marbling.

Library of Congress Subject Headings

Lipids -- Metabolism
Fatty acids




South Dakota State University