There is provided a method of treating a weaning piglet with a cortisol agonist where the method includes administering a dose of the cortisol agonist to the weaning piglet, in a therapeutically effective amount, to cause an increase in body mass as compared to a like weaning but untreated piglet. The cortisol agonist may be dexamethasone. Further, the dose may range from about 0.1 mg/kg body mass to about 1.0 mg/kg of body mass, administered via intra-muscular injection. In a particular exemplary embodiment, the method includes administering a dose of 0.2 mg/kg body mass via intra-muscular injection. The method may include administering a first dose before weaning, and administering a second dose after weaning. Further, the first dose may be administered a day before commencing weaning, and the second dose 3 days after weaning has commenced.
