Sympathoadrenal Neurochemistry and early weaning of swine

Three litters of pigs were weaned at 21 days of age, and 3 others were left with the sow. Pigs were killed at 21, 23, 28, or 39 days of age. Weaned pigs exhibited anxiety, gastrointestinal dysfunction, and decreased rate of body weight gain. Plasma glucose or liver glycogen concentrations were not decreased by weaning. Adrenal gland weights and tyrosine hydroxylase (EC 1.14.3a), dopamine beta-hydroxylase (EC 1.14.2.1), phenethanolamine-N-methyl transferase (EC 2.1.1), and monoamine oxidase (EC 1.4.3.4) activities were increased after weaning. Adrenal catecholamine and cortisol levels and dopa decarboxylase (EC 4.1.1.26) and catechol-o-methyl transferase (EC 2.1.1.6) activities were not significantly altered, although some increases were indicated. Cranial cervical ganglionic choline acetyltransferase (EC 2.3.1.6) and tyrosine hydroxylase activities were increased after weaning. Weaning of swine at 21 days of age is a stressful experience, and many effects persist for at least 18 days; however, growth was no longer impaired 18 days after weaning.