PROTEIN-BOUND AND UNBOUND FORMS OF PLASMA-CORTISOL IN PIGLETS AFTER CASTRATION AT 7 OR 14 DAYS OF AGE

Male piglets from seven litters were used to evaluate the long-term ef fects of castration and age at castration on the concentrations of cor tisol and its distribution in peripheral plasma. The piglets were allo tted to one of three groups of 12 animals according to whether they ha d been castrated at seven or 14 days old or left intact. The animals w ere weighed and blood samples were collected from the anterior vena ca va at three, seven, 10, 14, 17, 21, 28, 35 and 42 days of age. The pla sma concentrations of albumin, total protein, cortisol, and the percen tage distribution of cortisol. among corticosteroid binding globulin-b ound (CBG-bound), albumin-bound and unbound forms, were determined. Ca stration at seven or 14 days of age had no effect on any of the parame ters measured. In all the piglets, the percentage of unbound cortisol decreased (P<0.001) from 24.5 to 11.6 per cent over the period of samp ling. The percentage of CBG-bound cortisol increased (P<0.001) from 19 per cent on day 17 to 47 per cent on day 21, and albumin-bound cortis ol declined from 61 to 37 per cent over the same period. These results agree with previous findings of age-related changes in the percentage distribution of cortisol in the piglet and demonstrate that these pat terns are unaffected by castration.