INFLUENCE OF STIMULI FROM CHICKS ON BEHAVIOR AND CONCENTRATIONS OF PLASMA PROLACTIN AND LUTEINIZING-HORMONE IN INCUBATING HENS

Removal of eggs from the nests of incubating birds or substitution of eggs for chicks disrupts incubation behavior and induces changes in th e secretion of prolactin and luteinizing hormone (LH). The aim of the present study was to determine how different stimuli, such as physical contact with eggs and tactile, visual, and/or auditory cues from chic ks, interact to control the transition between incubation and brooding and to induce changes in prolactin and LH plasma concentrations. Phys ical contact with chicks, in the presence or absence of eggs, induced brooding behavior and an immediate fall in plasma prolactin concentrat ion and a gradual increase in LH concentration. Vocalizations, particu larly clucking and food calls, increased rapidly while incubation and nest attachment disappeared slowly. No change in plasma prolactin or L H concentration was observed in incubating hens which could hear and s ee or only hear chicks. These incubating hens showed no interest in ch icks and continued to incubate persistently. To conclude, tactile stim uli, alone or in combination with visual and/or auditory stimuli from newly hatched chicks, are the only cues that induce the transition fro m incubation to brooding and the associated decrease in prolactin secr etion and increase in LH secretion. (C) 1998 Academic Press.