Effects of poults on plasma concentrations of prolactin in Turkey hens incubating without eggs or a nest

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Abstract
1. Plasma prolactin (PRL) concentrations, total daylight sitting time and extent of brood patch development were compared in singly caged hens incubating without a nest or eggs and in penned hens incubating eggs in nest boxes. No significant differences were found in any of the three measures of incubation intensity. 2. When 10 newly‐hatched poults were placed in the cages of incubating hens their plasma PRL concentrations fell rapidly. No fall in plasma PRL was observed in hens that could see and hear, but not touch the poults. 3. When physical contact between hens and poults was maintained, visual isolation of hens from poults, surgical devocalisation of poults, or the combination of visual isolation and devocalisation of poults had no effect on the poult‐stimulated decline in plasma PRL concentrations. 4. Sensory cues from poults that evoke the PRL response in incubating hens are primarily tactile.