The Interaction Between Pre-Laying Behaviour and Feeding in Hens: Implications for Motivation

Abstract

Abstract While considerable research has been undertaken on the hormonal basis of pre-laying behaviour of domestic hens (Gallus gallus domesticus), less is known about how the behaviour is initiated and about how changes in this behaviour occur. Two experiments were conducted to investigate aspects of the interaction of pre-laying behaviour with feeding motivation. Experiment 1 examined the effect of the absence of food. Pre-laying behaviour was observed in 20 laying hens either with or without food available. The duration of pre-laying behaviour was longer when deprived of food for short or long periods of time than for hens with access to food. The time of oviposition, however, appeared unchanged suggesting that motivation for pre-laying behaviour is initially increasing and that it competes with feeding behaviour for expression when food is available. Experiment 2 examined the effect of food in the absence of deprivation. The food of 17 hens was topped up at various intervals before oviposition. Contrary to expectation the delay in oviposition was greater (24 minutes) if food was presented closer to the expected oviposition (2 minutes) than if it was earlier (12 minutes before oviposition, which caused a delay of 12 minutes). When interrupted close to oviposition, most birds repeated part of the searching phase of pre-laying behaviour (7 minutes of searching as opposed to 3 minutes). It is concluded that a hypothesis based on competition between motivational systems offers a good predictor for the start of pre-laying behaviour, but not for the duration of interruption later in the pre-laying behaviour sequence.