Migratory fat deposition in European quail: a role for prolactin?

The present study addresses the role of prolactin as a regulator of migratory fattening in European quail (Coturnix coturnix). Plasma prolactin levels in captive birds undergoing migratory fattening in an outdoor aviary and in the laboratory were measured by radioimmunoassay with an antibody raised against recombinant-derived chicken prolactin. No strong association between prolactin and migratory fattening was apparent, and prolactin levels were more closely related to daylength, with the highest concentrations being reached on long days. Plasma prolactin profiles were similar in intact and castrated male quail. Prolactin was secreted in a daily rhythm, with the highest concentrations occurring early in the photophase. However, when birds were food-restricted for 50 days during a migratory phase, there was no difference in fat deposition between birds food-deprived for the first half of the daily photophase compared with those deprived for the second half. Fattening was reduced in the food-restricted birds relative to ad libitum-fed controls, but there was no difference in plasma prolactin levels between the groups. Injections of ovine prolactin (4 mg/kg) significantly increased food intake and body mass of birds maintained on long days, but there were no differences in fattening between birds injected in the morning compared with those injected in the afternoon. Collectively, these results do not support a major role for prolactin in the regulation of migratory fat deposition in European quail.