CZAAWE Resource Article

Feed-restricted broiler breeders: State-dependent learning as a novel welfare assessment tool to evaluate their hunger state?
Publication Type 
Journal Article
Year of publication 
Applied Animal Behaviour Science
This paper reports three experiments that aimed to validate the use of state-dependent learning (SDL) as a novel welfare assessment tool to evaluate the hunger state of feed-restricted broiler breeders. In each experiment, birds alternated every 2 days between two food rations: quantitative feed restriction (QFR) and ad libitum access to the same feed (AL). Each food ration was paired with a different, end of day, coloured food reward. It was predicted that the reward associated with hunger (QFR FR) would be preferred to the food reward associated with AL (AL FR) in a subsequent choice test. The SDL preference testing took place after 4 and 8 days of training. Each bird was tested twice (once per food ration fed on the test day). In experiment 1 (pilot, n = 4), birds preferred the QFR-associated reward during both tests (mean (±S.E.M.) preference: QFR FR: 35.0 (±3.5) g; AL FR: 2 (±1.3) g, but differential food reward intake between hunger states during training confounded the results. In experiment two (n = 12) a smaller food reward was used during training to try and equalise intake. The birds preferred the QFR FR in test 1 only (least significant difference (L.S.D.) = 15.08, P < 0.05). The mean (±S.E.M.) consumption in test 1 was: QFR FR: 31.6 (±4.3) g; AL FR: 9.41 (±2.3) g. However, differential reward intake continued to confound the findings. In experiment three (n = 8), the food reward was made more palatable by feeding moist and food reward intake during training was equalised between hunger states. During testing, birds continued to show a significant preference in test 1 only (L.S.D. = 13.73, P < 0.05). It was concluded that SDL-derived preferences observed do exist but are not a robust phenomenon. Therefore, further research is needed to quantify factors influencing SDL development and maintenance before using SDL as a tool to assess hunger in feed-restricted broiler breeders.