Qualitative feed restriction affects frustration, fear, motivation to explore, and feather fault bars in Ross 308 broiler breeder cockerels

Broiler breeders show behaviours indicative of hunger and frustration stemming from unfulfilled behavioural needs for feeding. This is largely due to quantitative feed restriction which is common practice in the management of these birds, particularly in the rearing period. As an alternative, qualitative feed restriction allows a larger portion of feed to be provided without increasing the caloric intake. While several studies have assessed the effects of qualitative feeding on female broiler breeders, no such assessment has been done on broiler breeder cockerels. The aim of this study was to investigate the effects of feed dilution and roughage on the level of stress, fear and motivation to explore of broiler breeder cockerels. 200 Ross 308 broiler breeder cockerels (between 5 and 10 weeks of age) were housed in 12 pens (6 pens/treatment), 17 birds/pen. The treatments were standard feed (Control) and feed diluted with 20 % insoluble oat hulls and 150 g of alfalfa roughage daily/pen (D+R). The D+R birds received 20 % more feed per day. Novel object (NO) and frustration during thwarted feeding tests were performed in the home pen and the response recorded with video cameras. In addition, four birds from each pen were subjected to a tonic immobility test (TI). All behavioural tests were performed once a week at 6, 8 and 10 weeks of age. Finally, after euthanasia, two feathers from each bird were plucked and macroscopically examined for the presence of fault bars. The control birds showed a tendency to approach the NO faster than the D+R birds (P = 0.07) and were more likely to approach at 10 weeks of age (P = 0.006). In the frustration test, D+R birds spent less time pecking the feed container (P = 0.049), more time standing (P = 0.01) and tended to have fewer behavioural transitions (P = 0.09) than control birds, which indicates a reduction in frustration levels. In addition, Control birds stayed in TI longer than D+R birds (160.7 ± 15.5 s and 98.1 ± 15.4, respectively. P = 0.005). However, D+R had more fault bars compared to Control birds (P = 0.02), highlighting that care is needed to interpret these contradicting results. Nevertheless, the results show that the combination of feed dilution and daily roughage can have positive effects on the welfare of broiler breeder cockerels by reducing the sensation of hunger as indicated by fear, frustration, and motivation to explore.