The use of conditioned place preference to determine broiler preferences for quantitative or qualitative dietary restriction

Abstract

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.