Indices of stress in housed experimental sheep

Six trained sheep were used in isotope dilution studies to determine the relations between glucose and lactate metabolism. The animals were judged by their behaviour and by their arterialplasma glucose and cortisol concentrations to be unstressed before and during each experiment. In each animal, however, the concentration of lactate in an arterial plasma sample taken immediately before an experiment was greater than the mean arterial plasma lactate concentration found during the course of the experiment. This increase in the concentration of lactate may be a sensitive index of apprehension in sheep which are well accustomed to being handled and which by other criteria appear to be unstressed.