Restrictively fed broiler breeders are known to have increased motivation to explore and reduced fearfulness because hunger increases the motivation to search for and to acquire food, forcing the birds to face and engage with aversive stimuli that they would otherwise avoid. The aim of this study was to compare the effects of four dietary treatments on the level of fear and motivation to explore during rearing. In total, 1200 female breeder chicks of the genotype Ross 308 were housed in 24 pens, six pens of 50 birds per treatment. The treatments were: 1) standard feed (Control), 2) feed containing insoluble fibres (Insoluble), 3) feed containing a mix of both insoluble and soluble fibres (Mixed) and 4) standard feed supplemented with maize silage (Roughage). The treatments followed a qualitative restriction feeding strategy meant to allow the birds to consume larger portions of feed, increasing feeding time and reducing hunger and frustration. A novel object (NO) test was performed in the home pens at 6, 13 and 18 weeks of age. The test was performed two times at each age: 1 h before feeding and 5 h after feeding. In addition, at 7 weeks of age, 12 birds from each pen from all treatment groups were subjected to a tonic immobility (TI) test. We hypothesised that the Control birds would be less fearful in the TI test and keep a shorter distance to the NO than the treatment birds. For the NO test, there was an effect of the interaction between treatment and time of day on the likelihood of the birds to approach the NO at all ages (P ≤ 0.0001). At 13 weeks of age, in the afternoon, birds from the Mixed treatment were more likely to approach the NO compared to the birds from the Insoluble and Roughage treatments (P = 0.003) and tended to be more likely to approach than Control birds (P = 0.009). This suggests that the Mixed birds were in a hungrier state at that moment and therefore more willing to approach a NO than the birds fed the other dietary treatments. There was no effect of treatment on the latency to touch the NO or on the TI test. The results show minimal effects of the three qualitative dietary treatments on fearfulness and motivation to explore in female broiler breeders during rearing and, therefore, do not provide evidence of decreased sensation of hunger.
|Publication Title||Applied Animal Behaviour Science|
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