EFFECT OF CONFINEMENT ON THE CIRCADIAN RHYTHM OF OVINE CORTISOL

Abstract
Department of Animal Science, University of California, Davis, California 95616, U.S.A. (Received 8 October 1974) Few studies have dealt with diurnal cortisol rhythm in sheep (McNatty, Cashmore & Young, 1972; McNatty & Young, 1973). The present results elucidate further the circadian rhythm of ovine plasma cortisol and describe the effect of sudden and continuous cage restraint. Experimental methods and conditions were reported in detail by Holley & Evans (1974). Six mature rams were sampled at 4 h intervals for 32 days. On day 17 the animals were placed singly in small cages. Throughout the experiment the sheep received lucerne pellets at 16.00 h and the lighting schedule was maintained at 14 h light: 10 h darkness. Plasma cortisol was determined in duplicate without correction for other steroids as described by Bassett & Hinks (1969) and adjusted for extraction efficiency. Fig. 1. Daily percentage variations (means ± s.e.m.) in plasma cortisol

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