The effect of magnesium aspartate, xylazine and morphine on the immobilization-induced increase in the levels of prolactin in turkey plasma.

The effect of pre-treating turkey poults (8 weeks old) with magnesium aspartate, xylazine or morphine on the concentration of prolactin (PRL) in plasma was studied in normal birds, and birds stressed with immobilization. Acute immobilization (2 h) without drug treatment increased significantly the PRL concentration in plasma. Pretreatment with magnesium aspartate (405 mg/ml) at intramuscular doses of 100, 200, and 400 mg/bird decreased significantly, in a dose-dependent manner, the PRL plasma concentration when compared with the immobilized birds. Drug treatment without immobilization had no significant effect on PRL concentration. Similar results were obtained with xylazine (20 mg/ml) when given to birds intramuscularly at doses of 5, 10, or 20 mg/bird, 1 h before immobilization. Morphine, at intramuscular doses of 5 or 10 mg/kg, did not affect significantly the prolactin concentration of immobilized turkeys. At a dose of 25 mg/kg, however, it significantly lowered the PRL plasma concentration in immobilized birds. Morphine treatment alone did not influence significantly the basal PRL plasma concentration.