Effects of previous experience on total blood and free iodothyronine responses to isolation, restraint and shearing in sheep (Ovis aries)

Abstract

ABSTRACT:The aim of this study was to investigate a possible effect on thyroid hormone concentrations in peripheral blood in sheep submitted to isolation, restraint and shearing. Circulating T 3 , T 4 , fT 3 and fT 4 concentrations of No. 40 Pinzirita sheep were evaluated under baseline conditions, 24 h before isolation, restraint and shearing (T0), after isolation (T1), and after restraint and shearing (T2), with respect to the influence of a previous shearing experience (just shorn). A control group of 40 sheep was evaluated under baseline conditions (T0). Two-way RM ANOVA showed a significant effect of previous experience and sex on T 3 (P ≤ 0.05) and fT 3 (P ≤ 0.01) changes, with lower T 3 and higher fT 3 concentrations in just shorn than in intact females; on T 4 (P ≤ 0.005), fT 3 (P ≤ 0.0001) and fT 4 (P ≤ 0.001) changes, with higher T 4 , fT 3 and fT 4 changes in just shorn than in intact females; on T 4 (P ≤ 0.001), fT 3 (P ≤ 0.0005) and fT 4 (P ≤ 0.001) changes, with higher T 4 , fT 3 and fT 4 changes in intact females than males. The magnitude of total and free iodothyronine changes following handling practices suggests that restraint and shearing represent a moderate stressor in sheep, while isolation is probably perceived as a severe stress stimulus.

The Influence of Shearing Stress on Thermal Homeostasis and Performance of Barki Ewes in the North Western Desert of Egypt

“…Even under mild climates, shearing corrupts heat balance mechanisms as it makes sheep more reliable to climatic stress after removing its insulating layer, fleece. Therefore, several changes could be expected in rectal temperature, skin temperature and respiration frequency [8], [23]and [27].The impact of shearing as stress stimulus ranges between moderate [11] to effective [12] stressor.…”