Date of Award

8-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Animal Physiology

Advisor

Gibbons, John

Committee Member

Riggs , Laura

Committee Member

Coverdale , Josie

Committee Member

Bodine , A B

Abstract

Excessive exercise may induce osteoarthritis (OA), or degeneration, of articular cartilage, which is a leading cause of lameness and decreased use in horses. The purposes of this study were to utilize a sheep model to determine the effects of circular and linear exercise on the macroscopic and microscopic characteristics of articular cartilage in the metacarpal-phalangeal (MCP) joint and to evaluate biochemical changes in serum and synovial fluid compared to non-exercised control lambs.
Twenty lambs were randomly assigned to three groups: circular exercise (C, 8.5m diameter; n = 8), straight-line exercise (S, treadmill; n = 8) and non-exercised control (CON, n = 4). Lambs (C and S) were exercised at 1.3 m/s over a 6- to 8-wk period. Serum and synovial fluid (SF) from the MCP joint was collected throughout the study. Upon euthanasia, MCP joints were collected and fixed for gross morphology and histological analysis. Serum was analyzed for total protein (STP), collagen Type II cleavage ¾ fragments (C2C) and lysyl oxidase (LOX) activity. Synovial fluid was analyzed for total protein (SFTP) and LOX activity for each MCP separately.
Circularly-exercised sheep had the most severe lesion development on the lateral condyle of the distal metacarpus compared to linearly-exercised and non-exercised control sheep. Histological morphology indicated the linearly-exercised sheep had more severe histology OA scores than the circularly-exercised and the non-exercised control lambs. Biochemically, STP was not different among treatment groups over the course of the study. There were no differences among groups for serum C2C concentrations or LOX over the course of the study. There was a polynomial response to serum LOX over time, with peak LOX specific activities being reached at Wk 9 and then decreasing throughout the duration of the study. There were no differences in SFTP or SF LOX specific activities among groups throughout the study. However, SF LOX specific activity did increase over time for all treatment groups.
Results from this study indicate that early forced exercise (1.3 m/s) in juvenile lambs for 6 to 8 wks is capable of altering gross and microscopic morphology of articular cartilage in the MCP joint. However, the biomarkers utilized in this study did not directly correlate to these physical changes.

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