Physiological and urinary metabolite responses to cold shock and confinement of sheep

Fourteen 15-kg hand-raised lambs were subjected to a control treatment or to one 3-hr, -5 C cold shock each day for 4 days. The greatest increase in heart rate occurred at the second hour of cold shock, when ambient temperatures were lowest. This increase became successively smaller each day. The greatest rectal temperature decreases occurred after 3 hr of cold shock, 1 hr after the minimum ambient temperature had been reached. This rectal temperature decrease became successively greater each day as the lambs habituated to the cold shocks. Urinary calcium excretion was 67% higher (P less than .05) in the cold-shocked lambs than in the controls during the 18-hr intervals following the shock. Urinary cortisol excretion was different only on day 2, when the control group showed higher (P less than .05) values. A confinement stress was induced by the placing of four lambs in metabolic cages 5 days after they were removed from a range environment. These lambs were compared to four other lambs in metabolic cages which had been reared in the laboratory. Confinement stress increased urinary cortisol excretion (P less than .05) above that of the laboratory-reared lambs for the first 3 days. A mean urinary cortisol excretion of 41 ng.MBS-1.mr-1 or 20 ng.mg.creatine-1 was found in lambs in the range and laboratory groups over the remainder of the study. The range lambs' nitrogen retention, measured after cortisol excretion returned to baseline, was greater (P less than .05) than that of the laboratory lambs.