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This study aimed to identify hungry broiler breeders (n = 12) preferences for quantitative (Control) or qualitative dietary restriction (QDR) in a closed economy environment. The QDR option was either 3 g calcium propionate/kg total feed (n = 6) or 300 g oat hulls/kg total feed (n = 6). Quantitatively restricted or QDR portions ensured equal growth regardless of choice. Birds were separately taught a Control diet versus no food and a QDR diet versus no food task to allow each diet's satiating properties to be learnt. Birds had to associate the T-maze coloured arms with dietary outcomes to immediately obtain food. Birds learnt this task easily (p<0.001). A choice between the Control diet and the QDR diet was then offered but neither group demonstrated a diet preference. Study modifications demonstrated this was not a failure to discriminate between the diets per se (the Control diet was strongly preferred under ad libitum conditions (p<0.001)) or novel colour combination confusion (the colour associated with food was immediately selected when two novel food versus no food colour combinations were offered (p<0.001)). Most birds still failed to show a significant preference when the Control diet quantity was increased by 50% to make it 'obviously' bigger and better. Therefore, it was concluded that the failure to show a dietary preference was due to task learning failure and not necessarily lack of dietary preference. Where a preference was observed it was always for the control diet. Possible reasons for this failure to learn are discussed.

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1. Calcium propionate (CAP) may improve the welfare of feed restricted broiler breeders by improving their satiety when included within the feed ration. However, the evidence for this is mixed. 2. This study used a closed economy conditioned place preference (CPP) task and aimed to identify whether broilers (as a model for broiler breeders) preferred an environment associated with quantitative food restriction (QFR) or an environment associated with a diet quality-adjusted by the inclusion of CAP. Birds taught to associate different environments with QFR and ad libitum (AL) access to feed were used to validate the methodology. 3. The two treatment groups were (1) QFR/AL (n = 12) in which birds alternated every 2 d between QFR and ad libitum access to food, and (2) QFR/CAP (n = 12) in which birds alternated every 2 d between QFR and QFR + calcium propionate (increased from 3-9% over the study period). Birds were taught to associate one diet option with vertical stripes and the other with horizontal black and white stripes. Each bird was tested twice for a CPP (once per diet). 4. QFR/AL birds showed a significant preference for the pen associated with ad libitum access to feed, but only when tested hungry (i.e. fed QFR on day of testing). QFR/CAP birds did not show a preference under either hunger state. 5. Reasons for the failure of QFR/CAP birds to show a preference are unclear but could include a lack of preference or failure to learn the task. 6. The existence of state-dependent effects indicates that care is needed in the design of future CPP studies and that the effect of calcium propionate and level of hunger on ability to learn a CPP needs further investigation.

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